Drop support for Android 4

new minSdk is 21

bramble-android/build.gradle

@@ -11,7 +11,7 @@ android {
 	}
 
 	defaultConfig {
-		minSdkVersion 16
+		minSdkVersion 21
 		targetSdkVersion 31
 		versionCode 10500
 		versionName "1.5.0"

bramble-android/src/main/java/org/briarproject/bramble/account/AndroidAccountManager.java

@@ -20,7 +20,6 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.GuardedBy;
 import javax.inject.Inject;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Arrays.asList;
 import static java.util.logging.Level.INFO;
 import static org.briarproject.bramble.util.IoUtils.deleteFileOrDir;
@@ -105,15 +104,11 @@ class AndroidAccountManager extends AccountManagerImpl
 		}
 		files.add(appContext.getFilesDir());
 		addIfNotNull(files, appContext.getExternalCacheDir());
-		if (SDK_INT >= 19) {
+		for (File file : appContext.getExternalCacheDirs()) {
-			for (File file : appContext.getExternalCacheDirs()) {
+			addIfNotNull(files, file);
-				addIfNotNull(files, file);
-			}
 		}
-		if (SDK_INT >= 21) {
+		for (File file : appContext.getExternalMediaDirs()) {
-			for (File file : appContext.getExternalMediaDirs()) {
+			addIfNotNull(files, file);
-				addIfNotNull(files, file);
-			}
 		}
 		// Clear the cache directory but don't delete it
 		File cacheDir = appContext.getCacheDir();

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPlugin.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.plugin.bluetooth;
 
+import android.annotation.SuppressLint;
 import android.app.Application;
 import android.bluetooth.BluetoothAdapter;
 import android.bluetooth.BluetoothDevice;
@@ -49,7 +50,6 @@ import static android.bluetooth.BluetoothAdapter.STATE_ON;
 import static android.bluetooth.BluetoothDevice.ACTION_FOUND;
 import static android.bluetooth.BluetoothDevice.DEVICE_TYPE_LE;
 import static android.bluetooth.BluetoothDevice.EXTRA_DEVICE;
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Collections.shuffle;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
@@ -60,6 +60,7 @@ import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
+@SuppressLint("MissingPermission")
 class AndroidBluetoothPlugin extends
 		AbstractBluetoothPlugin<BluetoothSocket, BluetoothServerSocket> {
 
@@ -253,7 +254,7 @@ class AndroidBluetoothPlugin extends
 					} else if (ACTION_FOUND.equals(action)) {
 						BluetoothDevice d = i.getParcelableExtra(EXTRA_DEVICE);
 						// Ignore Bluetooth LE devices
-						if (SDK_INT < 18 || d.getType() != DEVICE_TYPE_LE) {
+						if (d.getType() != DEVICE_TYPE_LE) {
 							String address = d.getAddress();
 							if (LOG.isLoggable(INFO))
 								LOG.info("Discovered " +

bramble-android/src/main/java/org/briarproject/bramble/plugin/tcp/AndroidLanTcpPlugin.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.plugin.tcp;
 
-import android.annotation.TargetApi;
 import android.app.Application;
 import android.net.ConnectivityManager;
 import android.net.LinkAddress;
@@ -37,7 +36,6 @@ import javax.net.SocketFactory;
 import static android.content.Context.CONNECTIVITY_SERVICE;
 import static android.content.Context.WIFI_SERVICE;
 import static android.net.NetworkCapabilities.TRANSPORT_WIFI;
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.list;
 import static java.util.Collections.singletonList;
@@ -118,7 +116,7 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 		// If there's no wifi IPv4 address, we might be a client on an
 		// IPv6-only wifi network. We can only detect this on API 21+
 		if (wifi == null) {
-			return SDK_INT >= 21 ? getWifiClientIpv6Address() : null;
+			return getWifiClientIpv6Address();
 		}
 		// Use the wifi IPv4 address to determine which interface's IPv6
 		// address we should return (if the interface has a suitable address)
@@ -172,7 +170,6 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	 * Returns a link-local IPv6 address for the wifi client interface, or null
 	 * if there's no such interface or it doesn't have a suitable address.
 	 */
-	@TargetApi(21)
 	@Nullable
 	private InetAddress getWifiClientIpv6Address() {
 		// https://issuetracker.google.com/issues/175055271
@@ -234,7 +231,6 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	// On API 21 and later, a socket that is not created with the wifi
 	// network's socket factory may try to connect via another network
 	private SocketFactory getSocketFactory() {
-		if (SDK_INT < 21) return SocketFactory.getDefault();
 		// https://issuetracker.google.com/issues/175055271
 		try {
 			for (Network net : connectivityManager.getAllNetworks()) {
@@ -302,7 +298,7 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 		Pair<InetAddress, Boolean> wifi = getWifiIpv4Address();
 		// If there's no wifi IPv4 address, we might be a client on an
 		// IPv6-only wifi network. We can only detect this on API 21+
-		if (wifi == null && SDK_INT >= 21) {
+		if (wifi == null) {
 			InetAddress ipv6 = getWifiClientIpv6Address();
 			if (ipv6 != null) return new Pair<>(ipv6, false);
 		}

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidSecureRandomProvider.java

@@ -31,8 +31,6 @@ import static android.provider.Settings.Secure.ANDROID_ID;
 @NotNullByDefault
 class AndroidSecureRandomProvider extends UnixSecureRandomProvider {
 
-	private static final int SEED_LENGTH = 32;
-
 	private final Context appContext;
 
 	@Inject
@@ -72,27 +70,6 @@ class AndroidSecureRandomProvider extends UnixSecureRandomProvider {
 		// Silence strict mode
 		StrictMode.ThreadPolicy tp = StrictMode.allowThreadDiskWrites();
 		super.writeSeed();
-		if (SDK_INT <= 18) applyOpenSslFix();
 		StrictMode.setThreadPolicy(tp);
 	}
-
-	// Based on https://android-developers.googleblog.com/2013/08/some-securerandom-thoughts.html
-	private void applyOpenSslFix() {
-		byte[] seed = new UnixSecureRandomSpi().engineGenerateSeed(
-				SEED_LENGTH);
-		try {
-			// Seed the OpenSSL PRNG
-			Class.forName("org.apache.harmony.xnet.provider.jsse.NativeCrypto")
-					.getMethod("RAND_seed", byte[].class)
-					.invoke(null, (Object) seed);
-			// Mix the output of the Linux PRNG into the OpenSSL PRNG
-			int bytesRead = (Integer) Class.forName(
-							"org.apache.harmony.xnet.provider.jsse.NativeCrypto")
-					.getMethod("RAND_load_file", String.class, long.class)
-					.invoke(null, "/dev/urandom", 1024);
-			if (bytesRead != 1024) throw new IOException();
-		} catch (Exception e) {
-			throw new SecurityException(e);
-		}
-	}
 }

bramble-android/src/main/java/org/briarproject/bramble/util/AndroidUtils.java

@@ -11,14 +11,10 @@ import org.briarproject.bramble.api.Pair;
 import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.io.File;
-import java.io.IOException;
 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-import java.util.ArrayList;
 import java.util.Collection;
-import java.util.List;
-import java.util.Scanner;
 
 import javax.annotation.Nullable;
 
@@ -29,7 +25,6 @@ import static android.content.pm.PackageManager.PERMISSION_GRANTED;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.os.Process.myPid;
 import static android.os.Process.myUid;
-import static java.lang.Runtime.getRuntime;
 import static java.util.Arrays.asList;
 import static org.briarproject.nullsafety.NullSafety.requireNonNull;
 
@@ -43,14 +38,7 @@ public class AndroidUtils {
 	private static final String STORED_LOGCAT = "dev-logcat";
 
 	public static Collection<String> getSupportedArchitectures() {
-		List<String> abis = new ArrayList<>();
+		return asList(Build.SUPPORTED_ABIS);
-		if (SDK_INT >= 21) {
-			abis.addAll(asList(Build.SUPPORTED_ABIS));
-		} else {
-			abis.add(Build.CPU_ABI);
-			if (Build.CPU_ABI2 != null) abis.add(Build.CPU_ABI2);
-		}
-		return abis;
 	}
 
 	public static boolean hasBtConnectPermission(Context ctx) {
@@ -136,19 +124,6 @@ public class AndroidUtils {
 		return new String[] {"image/jpeg", "image/png", "image/gif"};
 	}
 
-	@Nullable
-	public static String getSystemProperty(String propName) {
-		try {
-			Process p = getRuntime().exec("getprop " + propName);
-			Scanner s = new Scanner(p.getInputStream());
-			String line = s.nextLine();
-			s.close();
-			return line;
-		} catch (SecurityException | IOException e) {
-			return null;
-		}
-	}
-
 	public static boolean isUiThread() {
 		return Looper.myLooper() == Looper.getMainLooper();
 	}

briar-android/build.gradle

@@ -24,7 +24,7 @@ android {
 	}
 
 	defaultConfig {
-		minSdkVersion 16
+		minSdkVersion 21
 		targetSdkVersion 31
 		versionCode 10500
 		versionName "1.5.0"
@@ -62,7 +62,6 @@ android {
 	productFlavors {
 		screenshot {
 			dimension "version"
-			minSdkVersion 21
 			applicationIdSuffix ".screenshot" // = org.briarproject.briar.android.screenshot.debug
 			proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt', 'proguard-test.txt'
 		}

briar-android/src/main/AndroidManifest.xml

@@ -99,11 +99,6 @@
 			android:exported="false"
 			android:label="@string/app_name" />
 
-		<activity
-			android:name="org.briarproject.briar.android.splash.ExpiredOldAndroidActivity"
-			android:exported="false"
-			android:label="@string/app_name" />
-
 		<activity
 			android:name="org.briarproject.briar.android.login.StartupActivity"
 			android:exported="false"

briar-android/src/main/java/org/briarproject/briar/android/AndroidNotificationManagerImpl.java

@@ -294,10 +294,8 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 		b.setOngoing(true);
 		Intent i = new Intent(appContext, SplashScreenActivity.class);
 		b.setContentIntent(getActivity(appContext, 0, i, getImmutableFlags(0)));
-		if (SDK_INT >= 21) {
+		b.setCategory(CATEGORY_SERVICE);
-			b.setCategory(CATEGORY_SERVICE);
+		b.setVisibility(VISIBILITY_SECRET);
-			b.setVisibility(VISIBILITY_SECRET);
-		}
 		b.setPriority(PRIORITY_MIN);
 		return b.build();
 	}
@@ -773,8 +771,7 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 		i.setAction(ACTION_STOP_HOTSPOT);
 		PendingIntent actionIntent =
 				getActivity(appContext, 0, i, getImmutableFlags(0));
-		int icon = SDK_INT >= 21 ? R.drawable.ic_portable_wifi_off : 0;
+		b.addAction(R.drawable.ic_portable_wifi_off, actionTitle, actionIntent);
-		b.addAction(icon, actionTitle, actionIntent);
 		notificationManager.notify(HOTSPOT_NOTIFICATION_ID, b.build());
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -212,7 +212,7 @@ public class AppModule {
 			public Collection<SimplexPluginFactory> getSimplexFactories() {
 				List<SimplexPluginFactory> simplex = new ArrayList<>();
 				simplex.add(mailbox);
-				if (SDK_INT >= 19) simplex.add(drive);
+				simplex.add(drive);
 				return simplex;
 			}
 

briar-android/src/main/java/org/briarproject/briar/android/Localizer.java

@@ -56,16 +56,8 @@ public class Localizer {
 	// Get Locale from BCP-47 tag
 	@Nullable
 	public static Locale getLocaleFromTag(String tag) {
-		if (tag.equals("default"))
+		if (tag.equals("default")) return null;
-			return null;
+		return Locale.forLanguageTag(tag);
-		if (SDK_INT >= 21) {
-			return Locale.forLanguageTag(tag);
-		}
-		if (tag.contains("-")) {
-			String[] langArray = tag.split("-");
-			return new Locale(langArray[0], langArray[1]);
-		} else
-			return new Locale(tag);
 	}
 
 	/*
@@ -94,12 +86,8 @@ public class Localizer {
 		if (locale.equals(currentLocale))
 			return context;
 		Locale.setDefault(locale);
-		if (SDK_INT >= 17) {
+		conf.setLocale(locale);
-			conf.setLocale(locale);
+		context = context.createConfigurationContext(conf);
-			context = context.createConfigurationContext(conf);
-		} else
-			conf.locale = locale;
-		//noinspection deprecation
 		res.updateConfiguration(conf, res.getDisplayMetrics());
 		return context;
 	}

briar-android/src/main/java/org/briarproject/briar/android/TestingConstants.java

@@ -2,8 +2,8 @@ package org.briarproject.briar.android;
 
 import org.briarproject.briar.BuildConfig;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.concurrent.TimeUnit.DAYS;
+import static org.briarproject.briar.BuildConfig.BuildTimestamp;
 
 public interface TestingConstants {
 
@@ -20,15 +20,9 @@ public interface TestingConstants {
 	 */
 	boolean PREVENT_SCREENSHOTS = !IS_DEBUG_BUILD;
 
-	boolean IS_OLD_ANDROID = SDK_INT <= 19;
-	long OLD_ANDROID_WARN_DATE = 1659225600_000L;   // 2022-07-31
-	long OLD_ANDROID_EXPIRY_DATE = 1675123200_000L; // 2023-01-31
-
 	/**
-	 * Debug builds expire after 90 days. Release builds running on Android 4
+	 * Debug builds expire after 90 days.
-	 * expire at a set date, otherwise they expire after 292 million years.
 	 */
 	long EXPIRY_DATE = IS_DEBUG_BUILD ?
-			BuildConfig.BuildTimestamp + DAYS.toMillis(90)
+			BuildTimestamp + DAYS.toMillis(90) : Long.MAX_VALUE;
-			: (IS_OLD_ANDROID ? OLD_ANDROID_EXPIRY_DATE : Long.MAX_VALUE);
 }

briar-android/src/main/java/org/briarproject/briar/android/account/UnlockActivity.java

@@ -32,7 +32,6 @@ import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_KEYGU
 import static org.briarproject.briar.android.util.UiUtils.hasKeyguardLock;
 import static org.briarproject.briar.android.util.UiUtils.hasUsableFingerprint;
 
-@RequiresApi(21)
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class UnlockActivity extends BaseActivity {

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityComponent.java

@@ -81,7 +81,6 @@ import org.briarproject.briar.android.sharing.ShareBlogFragment;
 import org.briarproject.briar.android.sharing.ShareForumActivity;
 import org.briarproject.briar.android.sharing.ShareForumFragment;
 import org.briarproject.briar.android.sharing.SharingModule;
-import org.briarproject.briar.android.splash.ExpiredOldAndroidActivity;
 import org.briarproject.briar.android.splash.SplashScreenActivity;
 import org.briarproject.briar.android.test.TestDataActivity;
 
@@ -184,8 +183,6 @@ public interface ActivityComponent {
 
 	void inject(RemovableDriveActivity activity);
 
-	void inject(ExpiredOldAndroidActivity activity);
-
 	// Fragments
 
 	void inject(SetupFragment fragment);

briar-android/src/main/java/org/briarproject/briar/android/activity/BriarActivity.java

@@ -24,7 +24,6 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import androidx.annotation.RequiresApi;
 import androidx.annotation.StringRes;
 import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.app.AlertDialog;
@@ -105,7 +104,7 @@ public abstract class BriarActivity extends BaseActivity {
 			LOG.info("Not signed in, launching StartupActivity");
 			Intent i = new Intent(this, StartupActivity.class);
 			startActivityForResult(i, REQUEST_PASSWORD);
-		} else if (SDK_INT >= 21 && lockManager.isLocked() && !isFinishing()) {
+		} else if (lockManager.isLocked() && !isFinishing()) {
 			// Also check that the activity isn't finishing already.
 			// This is possible if we finished in onActivityResult().
 			// Launching another UnlockActivity would cause a loop.
@@ -135,8 +134,7 @@ public abstract class BriarActivity extends BaseActivity {
 	 * @param exitTransition used to move views out when starting a <b>new</b> activity.
 	 * @param returnTransition used when window is closing, because the activity is finishing.
 	 */
-	@RequiresApi(api = 21)
+	protected void setSceneTransitionAnimation(
-	public void setSceneTransitionAnimation(
 			@Nullable Transition enterTransition,
 			@Nullable Transition exitTransition,
 			@Nullable Transition returnTransition) {
@@ -232,8 +230,7 @@ public abstract class BriarActivity extends BaseActivity {
 
 	@Wakeful
 	private void finishAndExit() {
-		if (SDK_INT >= 21) finishAndRemoveTask();
+		finishAndRemoveTask();
-		else supportFinishAfterTransition();
 		LOG.info("Exiting");
 		BriarApplication app = (BriarApplication) getApplication();
 		if (!app.isInstrumentationTest()) System.exit(0);

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogPostViewHolder.java

@@ -21,7 +21,6 @@ import androidx.annotation.UiThread;
 import androidx.core.view.ViewCompat;
 import androidx.recyclerview.widget.RecyclerView;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
@@ -134,12 +133,6 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 		} else {
 			reblogger.setVisibility(GONE);
 		}
-
-		// Apply Android 4 padding fix after setting up author/reblogger views
-		if (SDK_INT < 21) {
-			reblogger.setPadding(padding, padding, padding, padding);
-			author.setPadding(padding, padding, padding, padding);
-		}
 	}
 
 	private void onBindComment(BlogCommentItem item, boolean authorClickable) {

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedImportFragment.java

@@ -27,11 +27,9 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import androidx.activity.result.ActivityResultLauncher;
-import androidx.annotation.RequiresApi;
 import androidx.fragment.app.Fragment;
 import androidx.lifecycle.ViewModelProvider;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
 import static android.view.inputmethod.EditorInfo.IME_ACTION_DONE;
@@ -52,7 +50,6 @@ public class RssFeedImportFragment extends BaseFragment {
 	private Button importButton;
 	private ProgressBar progressBar;
 
-	@RequiresApi(19)
 	private final ActivityResultLauncher<String[]> docLauncher =
 			registerForActivityResult(new OpenDocumentAdvanced(),
 					this::onFileChosen);
@@ -74,7 +71,7 @@ public class RssFeedImportFragment extends BaseFragment {
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
 		requireActivity().setTitle(getString(R.string.blogs_rss_feeds_import));
-		if (SDK_INT >= 19) setHasOptionsMenu(true);
+		setHasOptionsMenu(true);
 		View v = inflater.inflate(R.layout.fragment_rss_feed_import,
 				container, false);
 
@@ -117,15 +114,13 @@ public class RssFeedImportFragment extends BaseFragment {
 
 	@Override
 	public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
-		if (SDK_INT >= 19) {
+		inflater.inflate(R.menu.rss_feed_import_actions, menu);
-			inflater.inflate(R.menu.rss_feed_import_actions, menu);
-		}
 		super.onCreateOptionsMenu(menu, inflater);
 	}
 
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item) {
-		if (item.getItemId() == R.id.action_import_file && SDK_INT >= 19) {
+		if (item.getItemId() == R.id.action_import_file) {
 			launchActivityToOpenFile(requireContext(), docLauncher,
 					contentLauncher, "*/*");
 			return true;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -55,7 +55,6 @@ import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener
 import org.briarproject.briar.android.introduction.IntroductionActivity;
 import org.briarproject.briar.android.privategroup.conversation.GroupActivity;
 import org.briarproject.briar.android.removabledrive.RemovableDriveActivity;
-import org.briarproject.briar.android.util.ActivityLaunchers.GetImageAdvanced;
 import org.briarproject.briar.android.util.ActivityLaunchers.GetMultipleImagesAdvanced;
 import org.briarproject.briar.android.util.ActivityLaunchers.OpenMultipleImageDocumentsAdvanced;
 import org.briarproject.briar.android.util.BriarSnackbarBuilder;
@@ -122,13 +121,11 @@ import androidx.vectordrawable.graphics.drawable.VectorDrawableCompat;
 import de.hdodenhof.circleimageview.CircleImageView;
 import uk.co.samuelwall.materialtaptargetprompt.MaterialTapTargetPrompt;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static android.view.Gravity.RIGHT;
 import static android.widget.Toast.LENGTH_SHORT;
 import static androidx.core.app.ActivityOptionsCompat.makeSceneTransitionAnimation;
 import static androidx.lifecycle.Lifecycle.State.STARTED;
 import static androidx.recyclerview.widget.SortedList.INVALID_POSITION;
-import static java.util.Collections.singletonList;
 import static java.util.Collections.sort;
 import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.INFO;
@@ -200,18 +197,13 @@ public class ConversationActivity extends BriarActivity
 		requireNonNull(name);
 		loadMessages();
 	};
-	@Nullable
+
-	private final ActivityResultLauncher<String[]> docLauncher = SDK_INT >= 19 ?
+	private final ActivityResultLauncher<String[]> docLauncher =
 			registerForActivityResult(new OpenMultipleImageDocumentsAdvanced(),
-					this::onImagesChosen) :
+					this::onImagesChosen);
-			null;
 	private final ActivityResultLauncher<String> contentLauncher =
-			SDK_INT >= 18 ?
+			registerForActivityResult(new GetMultipleImagesAdvanced(),
-					registerForActivityResult(new GetMultipleImagesAdvanced(),
+					this::onImagesChosen);
-							this::onImagesChosen) :
-					registerForActivityResult(new GetImageAdvanced(), uri -> {
-						if (uri != null) onImagesChosen(singletonList(uri));
-					});
 
 	private AttachmentRetriever attachmentRetriever;
 	private ConversationViewModel viewModel;
@@ -242,13 +234,11 @@ public class ConversationActivity extends BriarActivity
 
 	@Override
 	public void onCreate(@Nullable Bundle state) {
-		if (SDK_INT >= 21) {
+		// Spurious lint warning - using END causes a crash
-			// Spurious lint warning - using END causes a crash
+		@SuppressLint("RtlHardcoded")
-			@SuppressLint("RtlHardcoded")
+		Transition slide = new Slide(RIGHT);
-			Transition slide = new Slide(RIGHT);
+		slide.setDuration(TRANSITION_DURATION_MS);
-			slide.setDuration(TRANSITION_DURATION_MS);
+		setSceneTransitionAnimation(slide, null, slide);
-			setSceneTransitionAnimation(slide, null, slide);
-		}
 		super.onCreate(state);
 
 		Intent i = getIntent();
@@ -389,10 +379,6 @@ public class ConversationActivity extends BriarActivity
 						this::showIntroductionOnboarding);
 			}
 		});
-		// Transfer Data feature only supported on API 19+
-		if (SDK_INT >= 19) {
-			menu.findItem(R.id.action_transfer_data).setVisible(true);
-		}
 		// enable alias and bluetooth action once available
 		observeOnce(viewModel.getContactItem(), this, contact -> {
 			menu.findItem(R.id.action_set_alias).setEnabled(true);
@@ -434,11 +420,9 @@ public class ConversationActivity extends BriarActivity
 			startActivity(intent);
 			return true;
 		} else if (itemId == R.id.action_transfer_data) {
-			if (SDK_INT >= 19) {
+			Intent intent = new Intent(this, RemovableDriveActivity.class);
-				Intent intent = new Intent(this, RemovableDriveActivity.class);
+			intent.putExtra(CONTACT_ID, contactId.getInt());
-				intent.putExtra(CONTACT_ID, contactId.getInt());
+			startActivity(intent);
-				startActivity(intent);
-			}
 			return true;
 		} else if (itemId == R.id.action_delete_all_messages) {
 			askToDeleteAllMessages();
@@ -955,14 +939,10 @@ public class ConversationActivity extends BriarActivity
 
 	private void showImageOnboarding(Boolean show) {
 		if (!show) return;
-		if (SDK_INT >= 21) {
+		// show onboarding only after the enter transition has ended
-			// show onboarding only after the enter transition has ended
+		// otherwise the tap target animation won't play
-			// otherwise the tap target animation won't play
+		textInputView.postDelayed(this::showImageOnboarding,
-			textInputView.postDelayed(this::showImageOnboarding,
+				TRANSITION_DURATION_MS + ONBOARDING_DELAY_MS);
-					TRANSITION_DURATION_MS + ONBOARDING_DELAY_MS);
-		} else {
-			showImageOnboarding();
-		}
 	}
 
 	private void showImageOnboarding() {
@@ -973,14 +953,10 @@ public class ConversationActivity extends BriarActivity
 
 	private void showIntroductionOnboarding(@Nullable Boolean show) {
 		if (show == null || !show) return;
-		if (SDK_INT >= 21) {
+		// show onboarding only after the enter transition has ended
-			// show onboarding only after the enter transition has ended
+		// otherwise the tap target animation won't play
-			// otherwise the tap target animation won't play
+		textInputView.postDelayed(this::showIntroductionOnboarding,
-			textInputView.postDelayed(this::showIntroductionOnboarding,
+				TRANSITION_DURATION_MS + ONBOARDING_DELAY_MS);
-					TRANSITION_DURATION_MS + ONBOARDING_DELAY_MS);
-		} else {
-			showIntroductionOnboarding();
-		}
 	}
 
 	private void showIntroductionOnboarding() {

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageActivity.java

@@ -26,6 +26,7 @@ import org.briarproject.briar.android.util.BriarSnackbarBuilder;
 import org.briarproject.briar.android.view.PullDownLayout;
 import org.briarproject.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.nullsafety.ParametersNotNullByDefault;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.List;
 
@@ -41,13 +42,11 @@ import androidx.viewpager2.adapter.FragmentStateAdapter;
 import androidx.viewpager2.widget.ViewPager2;
 
 import static android.graphics.Color.TRANSPARENT;
-import static android.os.Build.VERSION.SDK_INT;
 import static android.view.View.GONE;
 import static android.view.View.SYSTEM_UI_FLAG_FULLSCREEN;
 import static android.view.View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN;
 import static android.view.View.SYSTEM_UI_FLAG_LAYOUT_STABLE;
 import static android.view.View.VISIBLE;
-import static android.view.WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS;
 import static com.google.android.material.snackbar.Snackbar.LENGTH_LONG;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.util.UiUtils.formatDateAbsolute;
@@ -77,11 +76,9 @@ public class ImageActivity extends BriarActivity
 	private List<AttachmentItem> attachments;
 	private MessageId conversationMessageId;
 
-	@Nullable
+	private final ActivityResultLauncher<String> launcher =
-	private final ActivityResultLauncher<String> launcher = SDK_INT >= 19 ?
 			registerForActivityResult(new CreateDocumentAdvanced(),
-					this::onImageUriSelected) :
+					this::onImageUriSelected);
-			null;
 
 	@Override
 	public void injectActivity(ActivityComponent component) {
@@ -97,10 +94,8 @@ public class ImageActivity extends BriarActivity
 		// Transitions
 		if (state == null) supportPostponeEnterTransition();
 		Window window = getWindow();
-		if (SDK_INT >= 21) {
+		Transition transition = new Fade();
-			Transition transition = new Fade();
+		setSceneTransitionAnimation(transition, null, transition);
-			setSceneTransitionAnimation(transition, null, transition);
-		}
 
 		// Intent Extras
 		Intent i = getIntent();
@@ -124,12 +119,7 @@ public class ImageActivity extends BriarActivity
 		layout.getViewTreeObserver().addOnGlobalLayoutListener(this);
 
 		// Status Bar
-		if (SDK_INT >= 21) {
+		window.setStatusBarColor(TRANSPARENT);
-			window.setStatusBarColor(TRANSPARENT);
-		} else if (SDK_INT >= 19) {
-			// we can't make the status bar transparent, but translucent
-			window.addFlags(FLAG_TRANSLUCENT_STATUS);
-		}
 
 		// Toolbar
 		appBarLayout = findViewById(R.id.appBarLayout);
@@ -257,16 +247,12 @@ public class ImageActivity extends BriarActivity
 
 	private void showSaveImageDialog() {
 		OnClickListener okListener = (dialog, which) -> {
-			if (SDK_INT >= 19) {
+			String name = viewModel.getFileName() + "." +
-				String name = viewModel.getFileName() + "." +
+					getVisibleAttachment().getExtension();
-						getVisibleAttachment().getExtension();
+			try {
-				try {
+				launcher.launch(name);
-					requireNonNull(launcher).launch(name);
+			} catch (ActivityNotFoundException e) {
-				} catch (ActivityNotFoundException e) {
+				viewModel.onSaveImageError();
-					viewModel.onSaveImageError();
-				}
-			} else {
-				viewModel.saveImage(getVisibleAttachment());
 			}
 		};
 		Builder builder = new Builder(this, R.style.BriarDialogTheme);
@@ -295,7 +281,7 @@ public class ImageActivity extends BriarActivity
 				.show();
 	}
 
-	AttachmentItem getVisibleAttachment() {
+	private AttachmentItem getVisibleAttachment() {
 		return attachments.get(viewPager.getCurrentItem());
 	}
 
@@ -307,6 +293,7 @@ public class ImageActivity extends BriarActivity
 			super(ImageActivity.this);
 		}
 
+		@NotNull
 		@Override
 		public Fragment createFragment(int position) {
 			Fragment f = ImageFragment.newInstance(

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageFragment.java

@@ -31,7 +31,6 @@ import androidx.fragment.app.Fragment;
 import androidx.lifecycle.LifecycleOwner;
 import androidx.lifecycle.ViewModelProvider;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static android.widget.ImageView.ScaleType.FIT_START;
 import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
 import static org.briarproject.briar.android.attachment.AttachmentItem.State.AVAILABLE;
@@ -150,7 +149,7 @@ public class ImageFragment extends Fragment
 	public boolean onResourceReady(Drawable resource, Object model,
 			Target<Drawable> target, DataSource dataSource,
 			boolean isFirstResource) {
-		if (SDK_INT >= 21 && !(resource instanceof Animatable)) {
+		if (!(resource instanceof Animatable)) {
 			// set transition name only when not animatable,
 			// because the animation won't start otherwise
 			photoView.setTransitionName(

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageViewHolder.java

@@ -18,7 +18,6 @@ import androidx.annotation.DrawableRes;
 import androidx.recyclerview.widget.RecyclerView.ViewHolder;
 import androidx.recyclerview.widget.StaggeredGridLayoutManager.LayoutParams;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static android.widget.ImageView.ScaleType.CENTER_CROP;
 import static android.widget.ImageView.ScaleType.FIT_CENTER;
 import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
@@ -58,10 +57,8 @@ class ImageViewHolder extends ViewHolder {
 			loadImage(attachment, r);
 			imageView.setScaleType(CENTER_CROP);
 		}
-		if (SDK_INT >= 21) {
+		imageView.setTransitionName(
-			imageView.setTransitionName(
+				attachment.getTransitionName(conversationItemId));
-					attachment.getTransitionName(conversationItemId));
-		}
 	}
 
 	private void setImageViewDimensions(AttachmentItem a, boolean single,

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumPostItem.java

@@ -1,8 +1,5 @@
 package org.briarproject.briar.android.forum;
 
-import org.briarproject.bramble.api.identity.Author;
-import org.briarproject.briar.api.identity.AuthorInfo;
-import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.android.threaded.ThreadItem;
 import org.briarproject.briar.api.forum.ForumPostHeader;
 

briar-android/src/main/java/org/briarproject/briar/android/hotspot/FallbackFragment.java

@@ -2,7 +2,6 @@ package org.briarproject.briar.android.hotspot;
 
 import android.content.Context;
 import android.content.Intent;
-import android.content.pm.ResolveInfo;
 import android.net.Uri;
 import android.os.Bundle;
 import android.view.LayoutInflater;
@@ -17,8 +16,6 @@ import org.briarproject.briar.android.util.ActivityLaunchers.CreateDocumentAdvan
 import org.briarproject.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.nullsafety.ParametersNotNullByDefault;
 
-import java.util.List;
-
 import javax.inject.Inject;
 
 import androidx.activity.result.ActivityResultLauncher;
@@ -29,14 +26,11 @@ import androidx.lifecycle.ViewModelProvider;
 import static android.content.Intent.ACTION_SEND;
 import static android.content.Intent.EXTRA_STREAM;
 import static android.content.Intent.FLAG_GRANT_READ_URI_PERMISSION;
-import static android.content.pm.PackageManager.MATCH_DEFAULT_ONLY;
-import static android.os.Build.VERSION.SDK_INT;
 import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
 import static androidx.transition.TransitionManager.beginDelayedTransition;
 import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 import static org.briarproject.briar.android.hotspot.HotspotViewModel.getApkFileName;
-import static org.briarproject.nullsafety.NullSafety.requireNonNull;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -48,11 +42,9 @@ public class FallbackFragment extends BaseFragment {
 	ViewModelProvider.Factory viewModelFactory;
 
 	private HotspotViewModel viewModel;
-	@Nullable
+	private final ActivityResultLauncher<String> launcher =
-	private final ActivityResultLauncher<String> launcher = SDK_INT >= 19 ?
 			registerForActivityResult(new CreateDocumentAdvanced(),
-					this::onDocumentCreated) :
+					this::onDocumentCreated);
-			null;
 	private Button fallbackButton;
 	private ProgressBar progressBar;
 
@@ -89,12 +81,7 @@ public class FallbackFragment extends BaseFragment {
 			beginDelayedTransition((ViewGroup) v);
 			fallbackButton.setVisibility(INVISIBLE);
 			progressBar.setVisibility(VISIBLE);
-
+			launcher.launch(getApkFileName());
-			if (SDK_INT >= 19) {
-				requireNonNull(launcher).launch(getApkFileName());
-			} else {
-				viewModel.exportApk();
-			}
 		});
 		viewModel.getSavedApkToUri().observeEvent(this, this::shareUri);
 	}
@@ -110,23 +97,11 @@ public class FallbackFragment extends BaseFragment {
 		progressBar.setVisibility(INVISIBLE);
 	}
 
-	void shareUri(Uri uri) {
+	private void shareUri(Uri uri) {
 		Intent i = new Intent(ACTION_SEND);
 		i.putExtra(EXTRA_STREAM, uri);
 		i.setType("*/*"); // gives us all sharing options
 		i.addFlags(FLAG_GRANT_READ_URI_PERMISSION);
-		Context ctx = requireContext();
-		if (SDK_INT <= 19) {
-			// Workaround for Android bug:
-			// ctx.grantUriPermission also needed for Android 4
-			List<ResolveInfo> resInfoList = ctx.getPackageManager()
-					.queryIntentActivities(i, MATCH_DEFAULT_ONLY);
-			for (ResolveInfo resolveInfo : resInfoList) {
-				String packageName = resolveInfo.activityInfo.packageName;
-				ctx.grantUriPermission(packageName, uri,
-						FLAG_GRANT_READ_URI_PERMISSION);
-			}
-		}
 		startActivity(Intent.createChooser(i, null));
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotViewModel.java

@@ -25,7 +25,6 @@ import org.briarproject.nullsafety.NotNullByDefault;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
-import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.util.concurrent.Executor;
@@ -38,9 +37,6 @@ import androidx.annotation.UiThread;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
-import static android.os.Build.VERSION.SDK_INT;
-import static android.os.Environment.DIRECTORY_DOWNLOADS;
-import static android.os.Environment.getExternalStoragePublicDirectory;
 import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -168,7 +164,6 @@ class HotspotViewModel extends DbViewModel
 	}
 
 	void exportApk(Uri uri) {
-		if (SDK_INT < 19) throw new IllegalStateException();
 		try {
 			OutputStream out = getApplication().getContentResolver()
 					.openOutputStream(uri, "wt");
@@ -178,20 +173,6 @@ class HotspotViewModel extends DbViewModel
 		}
 	}
 
-	void exportApk() {
-		if (SDK_INT >= 19) throw new IllegalStateException();
-		File path = getExternalStoragePublicDirectory(DIRECTORY_DOWNLOADS);
-		//noinspection ResultOfMethodCallIgnored
-		path.mkdirs();
-		File file = new File(path, getApkFileName());
-		try {
-			OutputStream out = new FileOutputStream(file);
-			writeApk(out, Uri.fromFile(file));
-		} catch (FileNotFoundException e) {
-			handleException(e);
-		}
-	}
-
 	static String getApkFileName() {
 		return "briar" + (DEBUG ? "-debug-" : "-") + VERSION_NAME + ".apk";
 	}

briar-android/src/main/java/org/briarproject/briar/android/logout/ExitActivity.java

@@ -5,8 +5,6 @@ import android.os.Bundle;
 
 import java.util.logging.Logger;
 
-import static android.os.Build.VERSION.SDK_INT;
-
 public class ExitActivity extends Activity {
 
 	private static final Logger LOG =
@@ -15,8 +13,7 @@ public class ExitActivity extends Activity {
 	@Override
 	public void onCreate(Bundle state) {
 		super.onCreate(state);
-		if (SDK_INT >= 21) finishAndRemoveTask();
+		finishAndRemoveTask();
-		else finish();
 		LOG.info("Exiting");
 		System.exit(0);
 	}

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerActivity.java

@@ -75,15 +75,12 @@ import static org.briarproject.bramble.api.plugin.Plugin.State.ENABLING;
 import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
 import static org.briarproject.briar.android.BriarService.EXTRA_STARTUP_FAILED;
 import static org.briarproject.briar.android.BriarService.EXTRA_START_RESULT;
-import static org.briarproject.briar.android.TestingConstants.EXPIRY_DATE;
 import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PASSWORD;
 import static org.briarproject.briar.android.navdrawer.IntentRouter.handleExternalIntent;
-import static org.briarproject.briar.android.util.UiUtils.formatDateFull;
 import static org.briarproject.briar.android.util.UiUtils.getDaysUntilExpiry;
 import static org.briarproject.briar.android.util.UiUtils.observeOnce;
 import static org.briarproject.briar.android.util.UiUtils.resolveColorAttribute;
-import static org.briarproject.briar.android.util.UiUtils.shouldWarnOldAndroidExpiry;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -140,11 +137,9 @@ public class NavDrawerActivity extends BriarActivity implements
 		setContentView(R.layout.activity_nav_drawer);
 
 		BriarApplication app = (BriarApplication) getApplication();
-		if (!app.isInstrumentationTest()) {
+		if (IS_DEBUG_BUILD && !app.isInstrumentationTest()) {
-			if (IS_DEBUG_BUILD || shouldWarnOldAndroidExpiry()) {
+			navDrawerViewModel.showExpiryWarning()
-				navDrawerViewModel.showExpiryWarning()
+					.observe(this, this::showExpiryWarning);
-						.observe(this, this::showExpiryWarning);
-			}
 		}
 		navDrawerViewModel.shouldAskForDozeWhitelisting().observe(this, ask -> {
 			if (ask) showDozeDialog(R.string.dnkm_doze_intro);
@@ -212,7 +207,7 @@ public class NavDrawerActivity extends BriarActivity implements
 	public void onStart() {
 		super.onStart();
 		lockManager.checkIfLockable();
-		if (IS_DEBUG_BUILD || shouldWarnOldAndroidExpiry()) {
+		if (IS_DEBUG_BUILD) {
 			navDrawerViewModel.checkExpiryWarning();
 		}
 	}
@@ -384,23 +379,14 @@ public class NavDrawerActivity extends BriarActivity implements
 			return;
 		}
 
-		String text;
-		if (IS_DEBUG_BUILD) {
-			text = getResources().getQuantityString(
-					R.plurals.expiry_warning, (int) daysUntilExpiry,
-					(int) daysUntilExpiry);
-		} else {
-			text = getResources().getQuantityString(
-					R.plurals.old_android_expiry_warning, (int) daysUntilExpiry,
-					formatDateFull(this, EXPIRY_DATE),
-					(int) daysUntilExpiry);
-		}
-
 		ViewGroup expiryWarning = findViewById(R.id.expiryWarning);
 		if (show) {
 			// show expiry warning text
 			TextView expiryWarningText =
 					expiryWarning.findViewById(R.id.expiryWarningText);
+			String text = getResources().getQuantityString(
+					R.plurals.expiry_warning, (int) daysUntilExpiry,
+					(int) daysUntilExpiry);
 			expiryWarningText.setText(text);
 			// make close button functional
 			ImageView expiryWarningClose =
@@ -432,7 +418,7 @@ public class NavDrawerActivity extends BriarActivity implements
 			}
 
 			@Override
-			public View getView(int position, View convertView,
+			public View getView(int position, @Nullable View convertView,
 					ViewGroup parent) {
 				View view;
 				if (convertView != null) {

briar-android/src/main/java/org/briarproject/briar/android/panic/PanicResponderActivity.java

@@ -19,7 +19,6 @@ import info.guardianproject.panic.Panic;
 import info.guardianproject.panic.PanicResponder;
 import info.guardianproject.trustedintents.TrustedIntents;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.android.panic.PanicPreferencesFragment.KEY_LOCK;
 import static org.briarproject.briar.android.panic.PanicPreferencesFragment.KEY_PURGE;
@@ -73,12 +72,7 @@ public class PanicResponderActivity extends BriarActivity {
 				}
 			}
 		}
-
+		finishAndRemoveTask();
-		if (SDK_INT >= 21) {
-			finishAndRemoveTask();
-		} else {
-			finish();
-		}
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/removabledrive/ReceiveFragment.java

@@ -20,7 +20,6 @@ import javax.inject.Inject;
 
 import androidx.activity.result.ActivityResultLauncher;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentActivity;
 import androidx.lifecycle.ViewModelProvider;
@@ -31,7 +30,6 @@ import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 import static org.briarproject.briar.android.util.UiUtils.hideViewOnSmallScreen;
 import static org.briarproject.briar.android.util.UiUtils.launchActivityToOpenFile;
 
-@RequiresApi(19)
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class ReceiveFragment extends Fragment {

briar-android/src/main/java/org/briarproject/briar/android/removabledrive/RemovableDriveActivity.java

@@ -19,7 +19,6 @@ import javax.inject.Inject;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.annotation.StringRes;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
@@ -29,7 +28,6 @@ import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
 import static org.briarproject.briar.android.util.UiUtils.showFragment;
 
-@RequiresApi(19)
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class RemovableDriveActivity extends BriarActivity {

briar-android/src/main/java/org/briarproject/briar/android/removabledrive/SendFragment.java

@@ -24,7 +24,6 @@ import javax.inject.Inject;
 
 import androidx.activity.result.ActivityResultLauncher;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentActivity;
 import androidx.lifecycle.ViewModelProvider;
@@ -38,7 +37,6 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 import static org.briarproject.briar.android.util.UiUtils.hideViewOnSmallScreen;
 
-@RequiresApi(19)
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class SendFragment extends Fragment {

briar-android/src/main/java/org/briarproject/briar/android/reporting/BriarReportCollector.java

@@ -220,10 +220,10 @@ class BriarReportCollector {
 				method.setAccessible(true);
 				mobileEnabled = (Boolean) requireNonNull(method.invoke(cm));
 			} catch (ClassNotFoundException
-					| NoSuchMethodException
+			         | NoSuchMethodException
-					| IllegalArgumentException
+			         | IllegalArgumentException
-					| InvocationTargetException
+			         | InvocationTargetException
-					| IllegalAccessException e) {
+			         | IllegalAccessException e) {
 				connectivityInfo
 						.add("MobileDataReflectionException", e.toString());
 			}
@@ -300,15 +300,12 @@ class BriarReportCollector {
 					scanMode == SCAN_MODE_CONNECTABLE_DISCOVERABLE;
 			connectivityInfo.add("BluetoothDiscoverable", btDiscoverable);
 
-			if (SDK_INT >= 21) {
+			// Is Bluetooth LE scanning and advertising supported?
-				// Is Bluetooth LE scanning and advertising supported?
+			boolean btLeScan = bt.getBluetoothLeScanner() != null;
-				boolean btLeScan = bt.getBluetoothLeScanner() != null;
+			connectivityInfo.add("BluetoothLeScanningSupported", btLeScan);
-				connectivityInfo.add("BluetoothLeScanningSupported", btLeScan);
+			boolean btLeAdvertise = bt.getBluetoothLeAdvertiser() != null;
-				boolean btLeAdvertise =
+			connectivityInfo.add("BluetoothLeAdvertisingSupported",
-						bt.getBluetoothLeAdvertiser() != null;
+					btLeAdvertise);
-				connectivityInfo.add("BluetoothLeAdvertisingSupported",
-						btLeAdvertise);
-			}
 
 			Pair<String, String> p = getBluetoothAddressAndMethod(ctx, bt);
 			String address = p.getFirst();

briar-android/src/main/java/org/briarproject/briar/android/settings/DisplayFragment.java

@@ -27,7 +27,6 @@ import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
 import static android.os.Build.VERSION.SDK_INT;
 import static androidx.core.view.ViewCompat.LAYOUT_DIRECTION_LTR;
 import static java.util.Objects.requireNonNull;
-import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.android.BriarApplication.ENTRY_ACTIVITY;
 import static org.briarproject.briar.android.navdrawer.NavDrawerActivity.SIGN_OUT_URI;
@@ -75,12 +74,6 @@ public class DisplayFragment extends PreferenceFragmentCompat {
 			Locale locale = Localizer.getLocaleFromTag(tag);
 			if (locale == null)
 				throw new IllegalStateException();
-			// Exclude RTL locales on API < 17, they won't be laid out correctly
-			if (SDK_INT < 17 && !isLeftToRight(locale)) {
-				if (LOG.isLoggable(INFO))
-					LOG.info("Skipping RTL locale " + tag);
-				continue;
-			}
 			String nativeName = locale.getDisplayName(locale);
 			// Fallback to English if the name is unknown in both native and
 			// current locale.

briar-android/src/main/java/org/briarproject/briar/android/settings/SecurityFragment.java

@@ -18,7 +18,6 @@ import androidx.preference.ListPreference;
 import androidx.preference.PreferenceFragmentCompat;
 import androidx.preference.SwitchPreferenceCompat;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 import static org.briarproject.briar.android.settings.SettingsActivity.enableAndPersist;
@@ -71,17 +70,12 @@ public class SecurityFragment extends PreferenceFragmentCompat {
 	@Override
 	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
 		super.onViewCreated(view, savedInstanceState);
-		if (SDK_INT < 21) {
+		// timeout depends on screenLock and gets disabled automatically
-			screenLock.setVisible(false);
+		LifecycleOwner lifecycleOwner = getViewLifecycleOwner();
-			screenLockTimeout.setVisible(false);
+		viewModel.getScreenLockTimeout().observe(lifecycleOwner, value -> {
-		} else {
+			screenLockTimeout.setValue(value);
-			// timeout depends on screenLock and gets disabled automatically
+			enableAndPersist(screenLockTimeout);
-			LifecycleOwner lifecycleOwner = getViewLifecycleOwner();
+		});
-			viewModel.getScreenLockTimeout().observe(lifecycleOwner, value -> {
-				screenLockTimeout.setValue(value);
-				enableAndPersist(screenLockTimeout);
-			});
-		}
 	}
 
 	@Override
@@ -92,7 +86,6 @@ public class SecurityFragment extends PreferenceFragmentCompat {
 	}
 
 	private void checkScreenLock() {
-		if (SDK_INT < 21) return;
 		LifecycleOwner lifecycleOwner = getViewLifecycleOwner();
 		viewModel.getScreenLockEnabled().removeObservers(lifecycleOwner);
 		if (hasScreenLock(requireActivity())) {

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java

@@ -24,7 +24,6 @@ import androidx.preference.Preference;
 import androidx.preference.PreferenceFragmentCompat;
 import androidx.preference.PreferenceGroup;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
@@ -49,11 +48,9 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 	private SettingsViewModel viewModel;
 	private AvatarPreference prefAvatar;
 
-	@Nullable
+	private final ActivityResultLauncher<String[]> docLauncher =
-	private final ActivityResultLauncher<String[]> docLauncher = SDK_INT >= 19 ?
 			registerForActivityResult(new OpenImageDocumentAdvanced(),
-					this::onImageSelected) :
+					this::onImageSelected);
-			null;
 	private final ActivityResultLauncher<String> contentLauncher =
 			registerForActivityResult(new GetImageAdvanced(),
 					this::onImageSelected);

briar-android/src/main/java/org/briarproject/briar/android/splash/ExpiredOldAndroidActivity.java

@@ -1,57 +0,0 @@
-package org.briarproject.briar.android.splash;
-
-import android.content.Intent;
-import android.os.Bundle;
-
-import org.briarproject.android.dontkillmelib.wakelock.AndroidWakeLockManager;
-import org.briarproject.briar.R;
-import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.activity.BaseActivity;
-import org.briarproject.briar.android.controller.BriarController;
-import org.briarproject.briar.android.logout.ExitActivity;
-import org.briarproject.nullsafety.MethodsNotNullByDefault;
-import org.briarproject.nullsafety.ParametersNotNullByDefault;
-
-import javax.annotation.Nullable;
-import javax.inject.Inject;
-
-import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TASK;
-import static android.content.Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS;
-import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
-import static android.content.Intent.FLAG_ACTIVITY_NO_ANIMATION;
-
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-public class ExpiredOldAndroidActivity extends BaseActivity {
-
-	@Inject
-	BriarController briarController;
-	@Inject
-	AndroidWakeLockManager wakeLockManager;
-
-	@Override
-	public void onCreate(@Nullable Bundle state) {
-		super.onCreate(state);
-
-		setContentView(R.layout.activity_expired_old_android);
-		findViewById(R.id.delete_account_button).setOnClickListener(v -> {
-			// Hold a wake lock to ensure we exit before the device goes to sleep
-			wakeLockManager.runWakefully(() -> {
-				// we're not signed in, just go ahead and delete
-				briarController.deleteAccount();
-				// remove from recent apps
-				Intent i = new Intent(this, ExitActivity.class);
-				i.addFlags(FLAG_ACTIVITY_NEW_TASK
-						| FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS
-						| FLAG_ACTIVITY_NO_ANIMATION
-						| FLAG_ACTIVITY_CLEAR_TASK);
-				startActivity(i);
-			}, "DeleteAccount");
-		});
-	}
-
-	@Override
-	public void injectActivity(ActivityComponent component) {
-		component.inject(this);
-	}
-}

briar-android/src/main/java/org/briarproject/briar/android/splash/SplashScreenActivity.java

@@ -21,7 +21,6 @@ import javax.inject.Inject;
 
 import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
 import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
-import static android.os.Build.VERSION.SDK_INT;
 import static androidx.preference.PreferenceManager.setDefaultValues;
 import static java.lang.System.currentTimeMillis;
 import static java.util.logging.Logger.getLogger;
@@ -50,12 +49,8 @@ public class SplashScreenActivity extends BaseActivity {
 	public void onCreate(@Nullable Bundle state) {
 		super.onCreate(state);
 
-		if (SDK_INT >= 21) {
+		getWindow().setExitTransition(new Fade());
-			getWindow().setExitTransition(new Fade());
-		}
-
 		setPreferencesDefaults();
-
 		setContentView(R.layout.splash);
 
 		if (accountManager.hasDatabaseKey()) {
@@ -65,14 +60,9 @@ public class SplashScreenActivity extends BaseActivity {
 			int duration =
 					getResources().getInteger(R.integer.splashScreenDuration);
 			new Handler().postDelayed(() -> {
-				if (currentTimeMillis() >= EXPIRY_DATE) {
+				if (IS_DEBUG_BUILD && currentTimeMillis() >= EXPIRY_DATE) {
-					if (IS_DEBUG_BUILD) {
+					LOG.info("Expired");
-						LOG.info("Expired: debug build");
+					startNextActivity(ExpiredActivity.class);
-						startNextActivity(ExpiredActivity.class);
-					} else {
-						LOG.info("Expired: running on old Android");
-						startNextActivity(ExpiredOldAndroidActivity.class);
-					}
 				} else {
 					startNextActivity(ENTRY_ACTIVITY);
 				}

briar-android/src/main/java/org/briarproject/briar/android/util/ActivityLaunchers.java

@@ -13,7 +13,6 @@ import androidx.activity.result.contract.ActivityResultContracts.OpenDocument;
 import androidx.activity.result.contract.ActivityResultContracts.OpenMultipleDocuments;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 
 import static android.app.Activity.RESULT_CANCELED;
 import static android.bluetooth.BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE;
@@ -26,7 +25,6 @@ import static org.briarproject.bramble.util.AndroidUtils.getSupportedImageConten
 @NotNullByDefault
 public class ActivityLaunchers {
 
-	@RequiresApi(19)
 	public static class CreateDocumentAdvanced extends CreateDocument {
 		@NonNull
 		@Override
@@ -48,7 +46,6 @@ public class ActivityLaunchers {
 		}
 	}
 
-	@RequiresApi(19)
 	public static class OpenDocumentAdvanced extends OpenDocument {
 		@NonNull
 		@Override
@@ -69,13 +66,11 @@ public class ActivityLaunchers {
 			putShowAdvancedExtra(i);
 			i.setType("image/*");
 			i.addFlags(FLAG_GRANT_READ_URI_PERMISSION);
-			if (SDK_INT >= 19)
+			i.putExtra(EXTRA_MIME_TYPES, getSupportedImageContentTypes());
-				i.putExtra(EXTRA_MIME_TYPES, getSupportedImageContentTypes());
 			return i;
 		}
 	}
 
-	@RequiresApi(18)
 	public static class GetMultipleImagesAdvanced extends GetMultipleContents {
 		@NonNull
 		@Override
@@ -84,13 +79,11 @@ public class ActivityLaunchers {
 			putShowAdvancedExtra(i);
 			i.setType("image/*");
 			i.addFlags(FLAG_GRANT_READ_URI_PERMISSION);
-			if (SDK_INT >= 19)
+			i.putExtra(EXTRA_MIME_TYPES, getSupportedImageContentTypes());
-				i.putExtra(EXTRA_MIME_TYPES, getSupportedImageContentTypes());
 			return i;
 		}
 	}
 
-	@RequiresApi(19)
 	public static class OpenImageDocumentAdvanced extends OpenDocument {
 		@NonNull
 		@Override
@@ -99,13 +92,11 @@ public class ActivityLaunchers {
 			putShowAdvancedExtra(i);
 			i.setType("image/*");
 			i.addFlags(FLAG_GRANT_READ_URI_PERMISSION);
-			if (SDK_INT >= 19)
+			i.putExtra(EXTRA_MIME_TYPES, getSupportedImageContentTypes());
-				i.putExtra(EXTRA_MIME_TYPES, getSupportedImageContentTypes());
 			return i;
 		}
 	}
 
-	@RequiresApi(19)
 	public static class OpenMultipleImageDocumentsAdvanced
 			extends OpenMultipleDocuments {
 		@NonNull
@@ -115,8 +106,7 @@ public class ActivityLaunchers {
 			putShowAdvancedExtra(i);
 			i.setType("image/*");
 			i.addFlags(FLAG_GRANT_READ_URI_PERMISSION);
-			if (SDK_INT >= 19)
+			i.putExtra(EXTRA_MIME_TYPES, getSupportedImageContentTypes());
-				i.putExtra(EXTRA_MIME_TYPES, getSupportedImageContentTypes());
 			return i;
 		}
 	}

briar-android/src/main/java/org/briarproject/briar/android/util/BriarNotificationBuilder.java

@@ -8,7 +8,6 @@ import androidx.annotation.ColorRes;
 import androidx.core.app.NotificationCompat;
 import androidx.core.content.ContextCompat;
 
-import static android.os.Build.VERSION.SDK_INT;
 import static androidx.core.app.NotificationCompat.VISIBILITY_PRIVATE;
 
 public class BriarNotificationBuilder extends NotificationCompat.Builder {
@@ -24,7 +23,7 @@ public class BriarNotificationBuilder extends NotificationCompat.Builder {
 
 		setLights(ContextCompat.getColor(context, R.color.briar_lime_400),
 				750, 500);
-		if (SDK_INT >= 21) setVisibility(VISIBILITY_PRIVATE);
+		setVisibility(VISIBILITY_PRIVATE);
 	}
 
 	public BriarNotificationBuilder setColorRes(@ColorRes int res) {
@@ -33,7 +32,7 @@ public class BriarNotificationBuilder extends NotificationCompat.Builder {
 	}
 
 	public BriarNotificationBuilder setNotificationCategory(String category) {
-		if (SDK_INT >= 21) setCategory(category);
+		setCategory(category);
 		return this;
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/util/BriarSnackbarBuilder.java

@@ -4,7 +4,6 @@ import android.view.View;
 import android.view.View.OnClickListener;
 
 import com.google.android.material.snackbar.Snackbar;
-import com.google.android.material.snackbar.Snackbar.Callback;
 
 import org.briarproject.briar.R;
 import org.briarproject.nullsafety.NotNullByDefault;
@@ -13,11 +12,7 @@ import androidx.annotation.ColorRes;
 import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
 
-import static android.os.Build.VERSION.SDK_INT;
-import static android.view.View.INVISIBLE;
-import static android.view.View.VISIBLE;
 import static androidx.core.content.ContextCompat.getColor;
-import static com.google.android.material.snackbar.Snackbar.LENGTH_INDEFINITE;
 
 @NotNullByDefault
 public class BriarSnackbarBuilder {
@@ -37,24 +32,6 @@ public class BriarSnackbarBuilder {
 					R.color.briar_button_text_positive));
 			s.setAction(actionResId, onClickListener);
 		}
-		// Workaround for https://issuetracker.google.com/issues/64285517
-		if (duration == LENGTH_INDEFINITE && SDK_INT < 21) {
-			// Hide snackbar while it's opening to make bouncing less noticeable
-			s.getView().setVisibility(INVISIBLE);
-			s.addCallback(new Callback() {
-				@Override
-				public void onShown(Snackbar snackbar) {
-					snackbar.getView().setVisibility(VISIBLE);
-					// Request layout again in case snackbar is in wrong place
-					snackbar.getView().requestLayout();
-				}
-
-				@Override
-				public void onDismissed(Snackbar snackbar, int event) {
-					snackbar.getView().setVisibility(INVISIBLE);
-				}
-			});
-		}
 		return s;
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/util/UiUtils.java

@@ -51,7 +51,6 @@ import androidx.annotation.ColorInt;
 import androidx.annotation.ColorRes;
 import androidx.annotation.DrawableRes;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.annotation.UiThread;
 import androidx.appcompat.app.AlertDialog;
 import androidx.core.content.ContextCompat;
@@ -108,8 +107,6 @@ import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.briar.android.TestingConstants.EXPIRY_DATE;
-import static org.briarproject.briar.android.TestingConstants.IS_OLD_ANDROID;
-import static org.briarproject.briar.android.TestingConstants.OLD_ANDROID_WARN_DATE;
 import static org.briarproject.briar.android.reporting.CrashReportActivity.EXTRA_APP_LOGCAT;
 import static org.briarproject.briar.android.reporting.CrashReportActivity.EXTRA_APP_START_TIME;
 import static org.briarproject.briar.android.reporting.CrashReportActivity.EXTRA_INITIAL_COMMENT;
@@ -244,11 +241,6 @@ public class UiUtils {
 		return (EXPIRY_DATE - now) / DAYS.toMillis(1);
 	}
 
-	public static boolean shouldWarnOldAndroidExpiry() {
-		return IS_OLD_ANDROID &&
-				System.currentTimeMillis() >= OLD_ANDROID_WARN_DATE;
-	}
-
 	public static SpannableStringBuilder getTeaser(Context ctx, Spanned text) {
 		if (text.length() < TEASER_LENGTH)
 			throw new IllegalArgumentException(
@@ -376,7 +368,6 @@ public class UiUtils {
 	}
 
 	public static boolean hasKeyguardLock(Context ctx) {
-		if (SDK_INT < 21) return false;
 		KeyguardManager keyguardManager =
 				(KeyguardManager) ctx.getSystemService(KEYGUARD_SERVICE);
 		if (keyguardManager == null) return false;
@@ -438,7 +429,6 @@ public class UiUtils {
 				keyEvent.getKeyCode() == KEYCODE_ENTER;
 	}
 
-	@RequiresApi(api = 21)
 	public static void excludeSystemUi(Transition transition) {
 		transition.excludeTarget(android.R.id.statusBarBackground, true);
 		transition.excludeTarget(android.R.id.navigationBarBackground, true);
@@ -480,7 +470,6 @@ public class UiUtils {
 	}
 
 	public static boolean isRtl(Context ctx) {
-		if (SDK_INT < 17) return false;
 		return ctx.getResources().getConfiguration().getLayoutDirection() ==
 				LAYOUT_DIRECTION_RTL;
 	}
@@ -507,7 +496,7 @@ public class UiUtils {
 		view.setVisibility(small ? GONE : VISIBLE);
 	}
 
-	public static boolean isSmallScreenRelativeToFontSize(Context ctx) {
+	private static boolean isSmallScreenRelativeToFontSize(Context ctx) {
 		Configuration config = ctx.getResources().getConfiguration();
 		if (config.fontScale == 0f) return true;
 		return config.screenHeightDp / config.fontScale < 600;
@@ -546,7 +535,7 @@ public class UiUtils {
 	}
 
 	public static void launchActivityToOpenFile(Context ctx,
-			@Nullable ActivityResultLauncher<String[]> docLauncher,
+			ActivityResultLauncher<String[]> docLauncher,
 			ActivityResultLauncher<String> contentLauncher,
 			String contentType) {
 		// Try GET_CONTENT, fall back to OPEN_DOCUMENT if available
@@ -556,13 +545,11 @@ public class UiUtils {
 		} catch (ActivityNotFoundException e) {
 			logException(LOG, WARNING, e);
 		}
-		if (docLauncher != null) {
+		try {
-			try {
+			docLauncher.launch(new String[] {contentType});
-				docLauncher.launch(new String[] {contentType});
+			return;
-				return;
+		} catch (ActivityNotFoundException e) {
-			} catch (ActivityNotFoundException e) {
+			logException(LOG, WARNING, e);
-				logException(LOG, WARNING, e);
-			}
 		}
 		Toast.makeText(ctx, R.string.error_start_activity, LENGTH_LONG).show();
 	}

briar-android/src/main/java/org/briarproject/briar/android/widget/TouchInterceptingLinearLayout.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.widget;
 
-import android.annotation.TargetApi;
 import android.content.Context;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
@@ -27,7 +26,6 @@ public class TouchInterceptingLinearLayout extends LinearLayout {
 		super(context, attrs, defStyleAttr);
 	}
 
-	@TargetApi(21)
 	public TouchInterceptingLinearLayout(Context context, AttributeSet attrs,
 			int defStyleAttr, int defStyleRes) {
 		super(context, attrs, defStyleAttr, defStyleRes);

briar-android/src/main/res/menu/conversation_actions.xml

@@ -35,7 +35,6 @@
 			<item
 				android:id="@+id/action_transfer_data"
 				android:title="@string/removable_drive_menu_title"
-				android:visible="false"
 				app:showAsAction="never" />
 		</menu>
 	</item>

briar-android/src/main/res/values/strings.xml

@@ -55,10 +55,6 @@
 		<item quantity="one">This is a test version of Briar. Your account will expire in %d day and cannot be renewed.</item>
 		<item quantity="other">This is a test version of Briar. Your account will expire in %d days and cannot be renewed.</item>
 	</plurals>
-	<plurals name="old_android_expiry_warning">
-		<item quantity="one">Android 4 is no longer supported. Briar will stop working on %s (in %d day). Please install Briar on a newer device and create a new account.</item>
-		<item quantity="other">Android 4 is no longer supported. Briar will stop working on %s (in %d days). Please install Briar on a newer device and create a new account.</item>
-	</plurals>
 	<string name="expiry_date_reached">This software has expired.\nThank you for testing!</string>
 	<string name="download_briar">To continue using Briar, please download the latest release.</string>
 	<string name="create_new_account">You will need to create a new account, but you can use the same nickname.</string>