Handle the don't keep activities option when using transfer data feature

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

@@ -47,6 +47,8 @@ public class ReceiveFragment extends Fragment {
 	private Button button;
 	private ProgressBar progressBar;
 
+	private boolean checkForStateLoss = false;
+
 	@Override
 	public void onAttach(Context context) {
 		super.onAttach(context);
@@ -73,6 +75,10 @@ public class ReceiveFragment extends Fragment {
 				.observeEvent(getViewLifecycleOwner(), this::onOldTaskResumed);
 		viewModel.getState()
 				.observe(getViewLifecycleOwner(), this::onStateChanged);
+
+		// need to check for lost ViewModel state when creating with prior state
+		if (savedInstanceState != null) checkForStateLoss = true;
+
 		return v;
 	}
 
@@ -84,6 +90,23 @@ public class ReceiveFragment extends Fragment {
 		scrollView.post(() -> scrollView.fullScroll(FOCUS_DOWN));
 	}
 
+	@Override
+	public void onResume() {
+		super.onResume();
+		// This code gets called *after* launcher had a chance
+		// to return the activity result.
+		if (checkForStateLoss && viewModel.hasNoState()) {
+			// We were recreated, but have lost the ViewModel state,
+			// because our activity was destroyed.
+			//
+			// Remove the current fragment from the stack
+			// to prevent duplicates on the back stack.
+			getParentFragmentManager().popBackStack();
+			// Start again (picks up existing task or allows to start a new one)
+			viewModel.startReceiveData();
+		}
+	}
+
 	private void onOldTaskResumed(boolean resumed) {
 		if (resumed) {
 			Toast.makeText(requireContext(),
@@ -104,6 +127,8 @@ public class ReceiveFragment extends Fragment {
 
 	private void onDocumentChosen(@Nullable Uri uri) {
 		if (uri == null) return;
+		// we just got our document, so don't treat this as a state loss
+		checkForStateLoss = false;
 		viewModel.importData(uri);
 	}
 

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

@@ -75,6 +75,12 @@ class RemovableDriveViewModel extends DbViewModel {
 		}
 	}
 
+	@UiThread
+	boolean hasNoState() {
+		return action.getLastValue() == null && state.getValue() == null &&
+				task == null;
+	}
+
 	/**
 	 * Set this as soon as it becomes available.
 	 */

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

@@ -51,6 +51,8 @@ public class SendFragment extends Fragment {
 	private Button button;
 	private ProgressBar progressBar;
 
+	private boolean checkForStateLoss = false;
+
 	@Override
 	public void onAttach(Context context) {
 		super.onAttach(context);
@@ -80,6 +82,9 @@ public class SendFragment extends Fragment {
 		viewModel.getState()
 				.observe(getViewLifecycleOwner(), this::onStateChanged);
 
+		// need to check for lost ViewModel state when creating with prior state
+		if (savedInstanceState != null) checkForStateLoss = true;
+
 		return v;
 	}
 
@@ -91,6 +96,23 @@ public class SendFragment extends Fragment {
 		scrollView.post(() -> scrollView.fullScroll(FOCUS_DOWN));
 	}
 
+	@Override
+	public void onResume() {
+		super.onResume();
+		// This code gets called *after* launcher had a chance
+		// to return the activity result.
+		if (checkForStateLoss && viewModel.hasNoState()) {
+			// We were recreated, but have lost the ViewModel state,
+			// because our activity was destroyed.
+			//
+			// Remove the current fragment from the stack
+			// to prevent duplicates on the back stack.
+			getParentFragmentManager().popBackStack();
+			// Start again (picks up existing task or allows to start a new one)
+			viewModel.startSendData();
+		}
+	}
+
 	private void onOldTaskResumed(boolean resumed) {
 		if (resumed) {
 			Toast.makeText(requireContext(),
@@ -127,6 +149,8 @@ public class SendFragment extends Fragment {
 
 	private void onDocumentCreated(@Nullable Uri uri) {
 		if (uri == null) return;
+		// we just got our document, so don't treat this as a state loss
+		checkForStateLoss = false;
 		viewModel.exportData(uri);
 	}