Check if there is data to send and show a message if not

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

@@ -60,8 +60,9 @@ public class ChooserFragment extends Fragment {
 	public void onStart() {
 		super.onStart();
 		requireActivity().setTitle(R.string.removable_drive_menu_title);
-		if (viewModel.getState().getValue() != null) {
+		TransferDataState state = viewModel.getState().getValue();
-			// we can't come back here now to start another action
+		if (state instanceof TransferDataState.TaskAvailable) {
+			// we can't come back here now to start another task
 			// as we only support one per ViewModel instance
 			requireActivity().supportFinishAfterTransition();
 		}

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

@@ -87,7 +87,7 @@ public class ReceiveFragment extends Fragment {
 		if (state instanceof TransferDataState.NoDataToSend) {
 			throw new IllegalStateException();
 		} else if (state instanceof TransferDataState.Ready) {
-			button.setVisibility(VISIBLE);
+			button.setEnabled(true);
 		} else if (state instanceof TransferDataState.TaskAvailable) {
 			button.setEnabled(false);
 			if (((TransferDataState.TaskAvailable) state).isOldTask) {

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

@@ -5,37 +5,38 @@ import android.net.Uri;
 
 import org.briarproject.bramble.api.Consumer;
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.file.RemovableDriveManager;
 import org.briarproject.bramble.api.plugin.file.RemovableDriveTask;
 import org.briarproject.bramble.api.plugin.file.RemovableDriveTask.State;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.android.viewmodel.DbViewModel;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 
 import java.text.SimpleDateFormat;
 import java.util.Date;
-import java.util.logging.Logger;
+import java.util.concurrent.Executor;
 
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import androidx.annotation.UiThread;
-import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
 import static java.util.Locale.US;
 import static java.util.Objects.requireNonNull;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.plugin.file.RemovableDriveConstants.PROP_URI;
 
 @UiThread
 @NotNullByDefault
-class RemovableDriveViewModel extends AndroidViewModel {
+class RemovableDriveViewModel extends DbViewModel {
-
-	private static final Logger LOG =
-			getLogger(RemovableDriveViewModel.class.getName());
 
 	enum Action {SEND, RECEIVE}
 
@@ -53,9 +54,14 @@ class RemovableDriveViewModel extends AndroidViewModel {
 	private Consumer<State> taskObserver = null;
 
 	@Inject
-	RemovableDriveViewModel(Application app,
+	RemovableDriveViewModel(
+			Application app,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager,
+			TransactionManager db,
+			AndroidExecutor androidExecutor,
 			RemovableDriveManager removableDriveManager) {
-		super(app);
+		super(app, dbExecutor, lifecycleManager, db, androidExecutor);
 		this.manager = removableDriveManager;
 	}
 
@@ -82,9 +88,19 @@ class RemovableDriveViewModel extends AndroidViewModel {
 		// check if there is already a send/write task
 		task = manager.getCurrentWriterTask();
 		if (task == null) {
-			// TODO check if there is data to export now
+			// check if there's even something to send
-			//  and only allow to continue if there is.
+			ContactId c = requireNonNull(contactId);
-			state.setValue(new TransferDataState.Ready());
+			runOnDbThread(() -> {
+				try {
+					if (manager.isWriterTaskNeeded(c)) {
+						state.postValue(new TransferDataState.Ready());
+					} else {
+						state.postValue(new TransferDataState.NoDataToSend());
+					}
+				} catch (DbException e) {
+					handleException(e);
+				}
+			});
 		} else {
 			// observe old task and start with initial state
 			taskObserver = s -> observeTask(s, true);

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

@@ -25,7 +25,7 @@ import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentActivity;
 import androidx.lifecycle.ViewModelProvider;
 
-import static android.view.View.GONE;
+import static android.os.Build.VERSION.SDK_INT;
 import static android.view.View.VISIBLE;
 import static android.widget.Toast.LENGTH_LONG;
 import static org.briarproject.briar.android.AppModule.getAndroidComponent;
@@ -47,6 +47,7 @@ public class SendFragment extends Fragment {
 	TextView introTextView;
 	Button button;
 	ProgressBar progressBar;
+	boolean hasShownOldTaskToast = false;
 
 	@Override
 	public void onAttach(Context context) {
@@ -86,14 +87,16 @@ public class SendFragment extends Fragment {
 	private void onStateChanged(TransferDataState state) {
 		if (state instanceof TransferDataState.NoDataToSend) {
 			introTextView.setText(R.string.removable_drive_send_no_data);
-			button.setVisibility(GONE);
+			button.setEnabled(false);
 		} else if (state instanceof TransferDataState.Ready) {
-			button.setVisibility(VISIBLE);
+			button.setEnabled(true);
 		} else if (state instanceof TransferDataState.TaskAvailable) {
 			button.setEnabled(false);
-			if (((TransferDataState.TaskAvailable) state).isOldTask) {
+			if (!hasShownOldTaskToast &&
+					((TransferDataState.TaskAvailable) state).isOldTask) {
 				Toast.makeText(requireContext(),
 						R.string.removable_drive_ongoing, LENGTH_LONG).show();
+				hasShownOldTaskToast = true;
 			}
 			RemovableDriveTask.State s =
 					((TransferDataState.TaskAvailable) state).state;
@@ -102,7 +105,11 @@ public class SendFragment extends Fragment {
 				// FIXME if we ever export more than 2 GB, this won't work
 				progressBar.setMax((int) s.getTotal());
 			}
-			progressBar.setProgress((int) s.getDone());
+			if (SDK_INT >= 24) {
+				progressBar.setProgress((int) s.getDone(), true);
+			} else {
+				progressBar.setProgress((int) s.getDone());
+			}
 		}
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/viewmodel/DbViewModel.java

@@ -23,7 +23,6 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.Immutable;
 
 import androidx.annotation.AnyThread;
-import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
 import androidx.arch.core.util.Function;
@@ -50,7 +49,7 @@ public abstract class DbViewModel extends AndroidViewModel {
 	protected final AndroidExecutor androidExecutor;
 
 	public DbViewModel(
-			@NonNull Application application,
+			Application application,
 			@DatabaseExecutor Executor dbExecutor,
 			LifecycleManager lifecycleManager,
 			TransactionManager db,

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

@@ -95,11 +95,10 @@
 		android:layout_width="0dp"
 		android:layout_height="wrap_content"
 		android:layout_margin="16dp"
+		android:enabled="false"
 		android:text="@string/removable_drive_receive_button"
-		android:visibility="gone"
 		app:layout_constraintBottom_toBottomOf="parent"
 		app:layout_constraintEnd_toEndOf="parent"
-		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintStart_toStartOf="parent" />
-		tools:visibility="visible" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>

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

@@ -98,11 +98,10 @@
 		android:layout_width="0dp"
 		android:layout_height="wrap_content"
 		android:layout_margin="16dp"
+		android:enabled="false"
 		android:text="@string/removable_drive_send_button"
-		android:visibility="gone"
 		app:layout_constraintBottom_toBottomOf="parent"
 		app:layout_constraintEnd_toEndOf="parent"
-		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintStart_toStartOf="parent" />
-		tools:visibility="visible" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>