Save the APK as a hotspot fallback

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

@@ -36,6 +36,7 @@ import org.briarproject.briar.android.attachment.AttachmentModule;
 import org.briarproject.briar.android.attachment.media.MediaModule;
 import org.briarproject.briar.android.conversation.glide.BriarModelLoader;
 import org.briarproject.briar.android.hotspot.AbstractTabsFragment;
+import org.briarproject.briar.android.hotspot.HotspotHelpFragment;
 import org.briarproject.briar.android.hotspot.HotspotIntroFragment;
 import org.briarproject.briar.android.hotspot.ManualHotspotFragment;
 import org.briarproject.briar.android.hotspot.QrHotspotFragment;
@@ -222,4 +223,6 @@ public interface AndroidComponent
 	void inject(QrHotspotFragment qrHotspotFragment);
 
 	void inject(ManualHotspotFragment manualHotspotFragment);
+
+	void inject(HotspotHelpFragment hotspotHelpFragment);
 }

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

@@ -1,16 +1,41 @@
 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;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.ProgressBar;
 
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 
+import java.util.List;
+
+import javax.inject.Inject;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.activity.result.contract.ActivityResultContracts.CreateDocument;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentActivity;
+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;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -18,6 +43,26 @@ public class HotspotHelpFragment extends Fragment {
 
 	public final static String TAG = HotspotHelpFragment.class.getName();
 
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private HotspotViewModel viewModel;
+	private final ActivityResultLauncher<String> launcher =
+			registerForActivityResult(new CreateDocument(), uri ->
+					viewModel.exportApk(uri)
+			);
+	private Button button;
+	private ProgressBar progressBar;
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		FragmentActivity activity = requireActivity();
+		getAndroidComponent(activity).inject(this);
+		viewModel = new ViewModelProvider(activity, viewModelFactory)
+				.get(HotspotViewModel.class);
+	}
+
 	@Override
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
@@ -25,4 +70,45 @@ public class HotspotHelpFragment extends Fragment {
 		return inflater
 				.inflate(R.layout.fragment_hotspot_help, container, false);
 	}
+
+	@Override
+	public void onViewCreated(View v, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(v, savedInstanceState);
+		button = v.findViewById(R.id.fallbackButton);
+		progressBar = v.findViewById(R.id.progressBar);
+		button.setOnClickListener(view -> {
+			beginDelayedTransition((ViewGroup) requireView());
+			button.setVisibility(INVISIBLE);
+			progressBar.setVisibility(VISIBLE);
+
+			if (SDK_INT >= 19) launcher.launch(getApkFileName());
+			else viewModel.exportApk();
+		});
+		viewModel.getSavedApkToUri().observeEvent(this, this::shareUri);
+	}
+
+	private void shareUri(Uri uri) {
+		beginDelayedTransition((ViewGroup) requireView());
+		button.setVisibility(VISIBLE);
+		progressBar.setVisibility(INVISIBLE);
+
+		Intent i = new Intent(ACTION_SEND);
+		i.putExtra(EXTRA_STREAM, uri);
+		i.setType("application/zip");
+		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

@@ -1,6 +1,7 @@
 package org.briarproject.briar.android.hotspot;
 
 import android.app.Application;
+import android.net.Uri;
 
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.TransactionManager;
@@ -21,6 +22,12 @@ import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 
+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;
 import java.util.logging.Logger;
 
@@ -31,8 +38,14 @@ 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.Logger.getLogger;
+import static org.briarproject.bramble.util.IoUtils.copyAndClose;
+import static org.briarproject.briar.BuildConfig.DEBUG;
+import static org.briarproject.briar.BuildConfig.VERSION_NAME;
 
 @NotNullByDefault
 class HotspotViewModel extends DbViewModel
@@ -51,6 +64,8 @@ class HotspotViewModel extends DbViewModel
 			new MutableLiveData<>();
 	private final MutableLiveEvent<Boolean> peerConnected =
 			new MutableLiveEvent<>();
+	private final MutableLiveEvent<Uri> savedApkToUri =
+			new MutableLiveEvent<>();
 
 	@Nullable
 	// Field to temporarily store the network config received via onHotspotStarted()
@@ -150,6 +165,48 @@ class HotspotViewModel extends DbViewModel
 		hotspotManager.stopWifiP2pHotspot();
 	}
 
+	void exportApk(Uri uri) {
+		if (SDK_INT < 19) throw new IllegalStateException();
+		try {
+			OutputStream out = getApplication().getContentResolver()
+					.openOutputStream(uri, "wt");
+			writeApk(out, uri);
+		} catch (FileNotFoundException e) {
+			handleException(e);
+		}
+	}
+
+	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";
+	}
+
+	private void writeApk(OutputStream out, Uri uriToShare) {
+		File apk = new File(getApplication().getPackageCodePath());
+		ioExecutor.execute(() -> {
+			try {
+				FileInputStream in = new FileInputStream(apk);
+				copyAndClose(in, out);
+				savedApkToUri.postEvent(uriToShare);
+			} catch (IOException e) {
+				handleException(e);
+			}
+		});
+	}
+
 	LiveData<HotspotState> getState() {
 		return state;
 	}
@@ -158,4 +215,8 @@ class HotspotViewModel extends DbViewModel
 		return peerConnected;
 	}
 
+	LiveEvent<Uri> getSavedApkToUri() {
+		return savedApkToUri;
+	}
+
 }

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

@@ -3,7 +3,6 @@ package org.briarproject.briar.android.hotspot;
 import android.content.Context;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.briar.BuildConfig;
 import org.briarproject.briar.R;
 import org.jsoup.Jsoup;
 import org.jsoup.nodes.Document;
@@ -29,6 +28,7 @@ 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.BuildConfig.VERSION_NAME;
+import static org.briarproject.briar.android.hotspot.HotspotViewModel.getApkFileName;
 
 @NotNullByDefault
 class WebServer extends NanoHTTPD {
@@ -80,8 +80,7 @@ class WebServer extends NanoHTTPD {
 		}
 		String app = ctx.getString(R.string.app_name);
 		String appV = app + " " + VERSION_NAME;
-		String filename = "briar" + (BuildConfig.DEBUG ? "-debug-" : "-") +
+		String filename = getApkFileName();
-				VERSION_NAME + ".apk";
 		doc.select("#download_title").first()
 				.text(ctx.getString(R.string.website_download_title, appV));
 		doc.select("#download_intro").first()

briar-android/src/main/res/layout/fragment_hotspot_help.xml

@@ -108,6 +108,49 @@
 			app:layout_constraintStart_toStartOf="parent"
 			app:layout_constraintTop_toBottomOf="@+id/site3View" />
 
+		<TextView
+			android:id="@+id/fallbackTitleView"
+			android:layout_width="0dp"
+			android:layout_height="wrap_content"
+			android:layout_marginTop="32dp"
+			android:text="@string/hotspot_help_fallback_title"
+			android:textSize="16sp"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintStart_toStartOf="parent"
+			app:layout_constraintTop_toBottomOf="@+id/site4View" />
+
+		<TextView
+			android:id="@+id/fallbackIntroView"
+			android:layout_width="0dp"
+			android:layout_height="wrap_content"
+			android:layout_marginTop="6dp"
+			android:text="@string/hotspot_help_fallback_intro"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintStart_toStartOf="parent"
+			app:layout_constraintTop_toBottomOf="@+id/fallbackTitleView" />
+
+		<Button
+			android:id="@+id/fallbackButton"
+			style="@style/BriarButton"
+			android:layout_width="0dp"
+			android:layout_height="wrap_content"
+			android:layout_margin="16dp"
+			android:text="@string/hotspot_help_fallback_button"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintStart_toStartOf="parent"
+			app:layout_constraintTop_toBottomOf="@+id/fallbackIntroView" />
+
+		<ProgressBar
+			android:id="@+id/progressBar"
+			style="?android:progressBarStyle"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:visibility="invisible"
+			app:layout_constraintBottom_toBottomOf="@+id/fallbackButton"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintStart_toStartOf="parent"
+			app:layout_constraintTop_toTopOf="@+id/fallbackButton" />
+
 	</androidx.constraintlayout.widget.ConstraintLayout>
 
 </ScrollView>

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

@@ -745,6 +745,10 @@
 	<string name="hotspot_help_site_2">Ensure that your phone is still connected to the correct Wi-Fi (see above) when you try to access the site.</string>
 	<string name="hotspot_help_site_3">Check that you don\'t have any active firewall apps that may block the access.</string>
 	<string name="hotspot_help_site_4">If you can visit the site, but not download the Briar app, try it with a different web browser app.</string>
+	<string name="hotspot_help_fallback_title">Nothing works?</string>
+	<string name="hotspot_help_fallback_intro">You can try to save the app as an .apk file to share in some other way. Once on the other device, it can be used to install Briar.
+		\n\nTip: For sharing via Bluetooth, you might need to rename the file to end with .zip first.</string>
+	<string name="hotspot_help_fallback_button">Save app install file</string>
 
 	<!-- Screenshots -->