Utilize a retained fragment to safekeep network requests in flight

pending result for openAddToPlaylistDialog() and openDownloadDialog()
Despite marked deprecated, setRetainInstance(true) is probably our best bet (since a ViewModel is probably too overkill for our present purpose)

app/src/main/java/org/schabi/newpipe/RouterActivity.java

@@ -83,9 +83,11 @@
 import org.schabi.newpipe.views.FocusOverlayView;
 
 import java.io.Serializable;
+import java.lang.ref.WeakReference;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Vector;
 
 import icepick.Icepick;
 import icepick.State;
@@ -300,7 +302,7 @@ private static void handleError(final Context context, final ErrorInfo errorInfo
  }
  }
 
- private void showUnsupportedUrlDialog(final String url) {
+ protected void showUnsupportedUrlDialog(final String url) {
  final Context context = getThemeWrapperContext();
  new AlertDialog.Builder(context)
  .setTitle(R.string.unsupported_url)
@@ -587,7 +589,7 @@ private List<AdapterChoiceItem> getChoicesForService(final StreamingService serv
  return returnedItems;
  }
 
- private Context getThemeWrapperContext() {
+ protected Context getThemeWrapperContext() {
  return new ContextThemeWrapper(this, ThemeHelper.isLightThemeSelected(this)
  ? R.style.LightTheme : R.style.DarkTheme);
  }
@@ -694,54 +696,175 @@ private boolean canHandleChoiceLikeShowInfo(final String selectedChoiceKey) {
  return playerType == null || playerType == PlayerType.MAIN;
  }
 
+ public static class PersistentFragment extends Fragment {
+ private WeakReference<AppCompatActivity> context;
+ private boolean isPaused = true;
+ private final Vector<ResultRunnable> buffer = new Vector<>();
+ private final CompositeDisposable disposables = new CompositeDisposable();
+
+ public interface ResultRunnable {
+ void run(AppCompatActivity context);
+ }
+
+ @Override
+ public void onAttach(@NonNull final Context activityContext) {
+ super.onAttach(activityContext);
+ context = new WeakReference<>((AppCompatActivity) activityContext);
+ }
+
+ @SuppressWarnings("deprecation")
+ @Override
+ public void onCreate(final Bundle savedInstanceState) {
+ super.onCreate(savedInstanceState);
+ setRetainInstance(true);
+ }
+
+ @Override
+ public void onDestroy() {
+ super.onDestroy();
+ disposables.clear();
+ }
+
+ @Override
+ public void onPause() {
+ isPaused = true;
+ super.onPause();
+ }
+
+ @Override
+ public void onResume() {
+ isPaused = false;
+ playback();
+ super.onResume();
+ }
+
+ private AppCompatActivity getActivityContext() {
+ return context == null ? null : context.get();
+ }
+
+ // guard against IllegalStateException in calling DialogFragment.show() whilst in background
+ // (which could happen, say, when the user pressed the home button while waiting for
+ // the network request to return) when it internally calls FragmentTransaction.commit()
+ // after the FragmentManager has saved its states (isStateSaved() == true)
+ // (ref: https://stackoverflow.com/a/39813506)
+ private void playback() {
+ if (activityGone()) {
+ done();
+ }
+ if (buffer.size() == 0 || isPaused) {
+ return;
+ }
+ while (buffer.size() > 0) {
+ final ResultRunnable runnable = buffer.elementAt(0);
+ buffer.removeElementAt(0);
+ getActivityContext().runOnUiThread(() -> {
+ // execute queued task with new context, in case activity has been recreated
+ runnable.run(getActivityContext());
+ });
+ }
+ done();
+ }
+ private boolean activityGone() {
+ return getActivityContext() == null || getActivityContext().isFinishing();
+ }
+
+ // a DefaultLifecycleObserver is probably a good candidate here, but for now
+ // let's stick with a vanilla approach to avoid pulling in an extra artifact just for this
+ private void runOnVisible(final ResultRunnable runnable) {
+ if (activityGone()) {
+ done();
+ }
+ if (isPaused) {
+ buffer.add(runnable);
+ if (!getActivityContext().isChangingConfigurations()) {
+ // try to bring the activity back to front if minimised
+ final Intent i = new Intent(getActivityContext(), RouterActivity.class);
+ i.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
+ startActivity(i);
+ }
+ } else {
+ getActivityContext().runOnUiThread(() -> {
+ runnable.run(getActivityContext());
+ done();
+ });
+ }
+ }
+
+ private void done() {
+ if (getActivityContext() != null) {
+ getActivityContext().getSupportFragmentManager()
+ .beginTransaction().remove(this).commit();
+ }
+ }
+
+ @SuppressLint("CheckResult")
+ protected void openDownloadDialog(final int currentServiceId, final String currentUrl) {
+ disposables.add(ExtractorHelper.getStreamInfo(currentServiceId, currentUrl, true)
+ .subscribeOn(Schedulers.io())
+ .observeOn(AndroidSchedulers.mainThread())
+ .subscribe(result ->
+ runOnVisible(ctx -> {
+ final FragmentManager fm = ctx.getSupportFragmentManager();
+ final DownloadDialog downloadDialog = new DownloadDialog(ctx, result);
+ // dismiss listener to be handled by FragmentManager
+ downloadDialog.show(fm, "downloadDialog");
+ }
+ ), throwable -> runOnVisible(ctx ->
+ ((RouterActivity) ctx).showUnsupportedUrlDialog(currentUrl))));
+ }
+
+ private void openAddToPlaylistDialog(final int currentServiceId, final String currentUrl) {
+ disposables.add(ExtractorHelper.getStreamInfo(currentServiceId, currentUrl, false)
+ .subscribeOn(Schedulers.io())
+ .observeOn(AndroidSchedulers.mainThread())
+ .subscribe(
+ info -> runOnVisible(ctx ->
+ PlaylistDialog.createCorrespondingDialog(
+ ((RouterActivity) ctx).getThemeWrapperContext(),
+ List.of(new StreamEntity(info)),
+ playlistDialog -> {
+ // dismiss listener to be handled by FragmentManager
+ final FragmentManager fm = ctx.getSupportFragmentManager();
+ playlistDialog.show(fm, "addToPlaylistDialog");
+ }
+ )),
+ throwable -> runOnVisible(ctx -> handleError(ctx, new ErrorInfo(
+ throwable,
+ UserAction.REQUESTED_STREAM,
+ "Tried to add " + currentUrl + " to a playlist",
+ ((RouterActivity) ctx).currentService.getServiceId())
+ ))
+ )
+ );
+ }
+ }
+
  private void openAddToPlaylistDialog() {
  pleaseWait();
 
- disposables.add(ExtractorHelper.getStreamInfo(currentServiceId, currentUrl, false)
- .subscribeOn(Schedulers.io())
- .observeOn(AndroidSchedulers.mainThread())
- .subscribe(
- info -> PlaylistDialog.createCorrespondingDialog(
- getThemeWrapperContext(),
- List.of(new StreamEntity(info)),
- playlistDialog -> {
- // to be handled by FragmentManager
- // playlistDialog.setOnDismissListener(dialog ->finish());
-
- final FragmentManager fm = getSupportFragmentManager();
- playlistDialog.show(fm, "addToPlaylistDialog");
- fm.executePendingTransactions();
- }
- ),
- throwable -> handleError(this, new ErrorInfo(
- throwable,
- UserAction.REQUESTED_STREAM,
- "Tried to add " + currentUrl + " to a playlist",
- currentService.getServiceId())
- )
- )
- );
+ getPersistFragment().openAddToPlaylistDialog(currentServiceId, currentUrl);
  }
 
- @SuppressLint("CheckResult")
  private void openDownloadDialog() {
  pleaseWait();
 
- disposables.add(ExtractorHelper.getStreamInfo(currentServiceId, currentUrl, true)
- .subscribeOn(Schedulers.io())
- .observeOn(AndroidSchedulers.mainThread())
- .subscribe(result -> {
- final DownloadDialog downloadDialog = new DownloadDialog(this, result);
- // to be handled by FragmentManager since listener would be gone when recreated
- // playlistDialog.setOnDismissListener(dialog ->finish());
-
- final FragmentManager fm = getSupportFragmentManager();
- downloadDialog.show(fm, "downloadDialog");
- fm.executePendingTransactions();
- }, throwable -> showUnsupportedUrlDialog(currentUrl)));
+ getPersistFragment().openDownloadDialog(currentServiceId, currentUrl);
+ }
+
+ private PersistentFragment getPersistFragment() {
+ final FragmentManager fm = getSupportFragmentManager();
+ PersistentFragment persistFragment =
+ (PersistentFragment) fm.findFragmentByTag("PERSIST_FRAGMENT");
+ if (persistFragment == null) {
+ persistFragment = new PersistentFragment();
+ fm.beginTransaction()
+ .add(persistFragment, "PERSIST_FRAGMENT")
+ .commitNow();
+ }
+ return persistFragment;
  }
 
- private void pleaseWait() {
+ protected void pleaseWait() {
  // Getting the stream info usually takes a moment
  // Notifying the user here to ensure that no confusion arises
  Toast.makeText(