-Added fling to toss popup view when velocity is below shutdown.

-Added string for unknown content.
-Fixed NPE when UI element is touched after player shuts down in service activity.
-Fixed shuffle reset caused by position discontinuity offsets index.
-Moved some more player shared preferences to PlayerHelper.

app/src/main/java/org/schabi/newpipe/player/BasePlayer.java

@@ -590,12 +590,12 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
         if (DEBUG) Log.d(TAG, "onPositionDiscontinuity() called with window index = [" + newWindowIndex + "]");
 
         // If the user selects a new track, then the discontinuity occurs after the index is changed.
-        // Therefore, the only source that causes a discrepancy would be autoplay,
+        // Therefore, the only source that causes a discrepancy would be gapless transition,
         // which can only offset the current track by +1.
-        if (newWindowIndex != playQueue.getIndex() && playbackManager != null) {
+        if (newWindowIndex == playQueue.getIndex() + 1) {
             playQueue.offsetIndex(+1);
-            playbackManager.load();
         }
+        playbackManager.load();
     }
 
     @Override
@@ -612,6 +612,8 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
         if (simpleExoPlayer == null) return;
         if (DEBUG) Log.d(TAG, "Blocking...");
 
+        currentItem = null;
+        currentInfo = null;
         simpleExoPlayer.stop();
         isPrepared = false;
 
@@ -642,8 +644,8 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
         // Check if on wrong window
         final int currentSourceIndex = playQueue.indexOf(item);
         if (currentSourceIndex != playQueue.getIndex()) {
-            throw new IllegalStateException("Play Queue may be desynchronized: item index=[" +
+            Log.e(TAG, "Play Queue may be desynchronized: item index=[" + currentSourceIndex +
-                    currentSourceIndex + "], queue index=[" + playQueue.getIndex() + "]");
+                    "], queue index=[" + playQueue.getIndex() + "]");
         } else if (simpleExoPlayer.getCurrentWindowIndex() != currentSourceIndex) {
             final long startPos = info != null ? info.start_position : 0;
             if (DEBUG) Log.d(TAG, "Rewinding to correct window: " + currentSourceIndex + " at: " + getTimeString((int)startPos));
@@ -829,15 +831,15 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
     }
 
     public String getVideoUrl() {
-        return currentItem == null ? null : currentItem.getUrl();
+        return currentItem == null ? context.getString(R.string.unknown_content) : currentItem.getUrl();
     }
 
     public String getVideoTitle() {
-        return currentItem == null ? null : currentItem.getTitle();
+        return currentItem == null ? context.getString(R.string.unknown_content) : currentItem.getTitle();
     }
 
     public String getUploaderName() {
-        return currentItem == null ? null : currentItem.getUploader();
+        return currentItem == null ? context.getString(R.string.unknown_content) : currentItem.getUploader();
     }
 
     public boolean isCompleted() {
@@ -873,8 +875,10 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
     }
 
     public PlaybackParameters getPlaybackParameters() {
+        final PlaybackParameters defaultParameters = new PlaybackParameters(1f, 1f);
+        if (simpleExoPlayer == null) return defaultParameters;
         final PlaybackParameters parameters = simpleExoPlayer.getPlaybackParameters();
-        return parameters == null ? new PlaybackParameters(1f, 1f) : parameters;
+        return parameters == null ? defaultParameters : parameters;
     }
 
     public void setPlaybackParameters(float speed, float pitch) {
@@ -903,7 +907,7 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
         final int queuePos = playQueue.getIndex();
         final long windowPos = simpleExoPlayer.getCurrentPosition();
 
-        if (windowPos > 0) {
+        if (windowPos > 0 && windowPos <= simpleExoPlayer.getDuration()) {
             setRecovery(queuePos, windowPos);
         }
     }

app/src/main/java/org/schabi/newpipe/player/PopupVideoPlayer.java

@@ -65,6 +65,7 @@ import org.schabi.newpipe.extractor.services.youtube.YoutubeStreamExtractor;
 import org.schabi.newpipe.extractor.stream.StreamInfo;
 import org.schabi.newpipe.extractor.stream.VideoStream;
 import org.schabi.newpipe.player.event.PlayerEventListener;
+import org.schabi.newpipe.player.helper.PlayerHelper;
 import org.schabi.newpipe.player.old.PlayVideoActivity;
 import org.schabi.newpipe.player.helper.LockManager;
 import org.schabi.newpipe.playlist.PlayQueueItem;
@@ -96,7 +97,6 @@ import static org.schabi.newpipe.util.AnimationUtils.animateView;
 public final class PopupVideoPlayer extends Service {
     private static final String TAG = ".PopupVideoPlayer";
     private static final boolean DEBUG = BasePlayer.DEBUG;
-    private static final int SHUTDOWN_FLING_VELOCITY = 10000;
 
     private static final int NOTIFICATION_ID = 40028922;
     public static final String ACTION_CLOSE = "org.schabi.newpipe.player.PopupVideoPlayer.CLOSE";
@@ -112,6 +112,9 @@ public final class PopupVideoPlayer extends Service {
     private WindowManager.LayoutParams windowLayoutParams;
     private GestureDetector gestureDetector;
 
+    private int shutdownFlingVelocity;
+    private int tossFlingVelocity;
+
     private float screenWidth, screenHeight;
     private float popupWidth, popupHeight;
 
@@ -211,12 +214,14 @@ public final class PopupVideoPlayer extends Service {
         View rootView = View.inflate(this, R.layout.player_popup, null);
         playerImpl.setup(rootView);
 
+        shutdownFlingVelocity = PlayerHelper.getShutdownFlingVelocity(this);
+        tossFlingVelocity = PlayerHelper.getTossFlingVelocity(this);
+
         updateScreenSize();
 
+        final boolean popupRememberSizeAndPos = PlayerHelper.isRememberingPopupDimensions(this);
+        final float defaultSize = getResources().getDimension(R.dimen.popup_default_width);
         SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
-        boolean popupRememberSizeAndPos = sharedPreferences.getBoolean(getString(R.string.popup_remember_size_pos_key), true);
-
-        float defaultSize = getResources().getDimension(R.dimen.popup_default_width);
         popupWidth = popupRememberSizeAndPos ? sharedPreferences.getFloat(POPUP_SAVED_WIDTH, defaultSize) : defaultSize;
 
         final int layoutParamType = Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.O ? WindowManager.LayoutParams.TYPE_PHONE : WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
@@ -791,11 +796,20 @@ public final class PopupVideoPlayer extends Service {
 
         @Override
         public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
+            if (DEBUG) Log.d(TAG, "Fling velocity: dX=[" + velocityX + "], dY=[" + velocityY + "]");
             if (playerImpl == null) return false;
-            if (Math.abs(velocityX) > SHUTDOWN_FLING_VELOCITY) {
+
-                if (DEBUG) Log.d(TAG, "Popup close fling velocity= " + velocityX);
+            final float absVelocityX = Math.abs(velocityX);
+            final float absVelocityY = Math.abs(velocityY);
+            if (absVelocityX > shutdownFlingVelocity) {
                 onClose();
                 return true;
+            } else if (Math.max(absVelocityX, absVelocityY) > tossFlingVelocity) {
+                if (absVelocityX > tossFlingVelocity) windowLayoutParams.x = (int) velocityX;
+                if (absVelocityY > tossFlingVelocity) windowLayoutParams.y = (int) velocityY;
+                checkPositionBounds();
+                windowManager.updateViewLayout(playerImpl.getRootView(), windowLayoutParams);
+                return true;
             }
             return false;
         }

app/src/main/java/org/schabi/newpipe/player/ServicePlayerActivity.java

@@ -286,6 +286,8 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
             item.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
                 @Override
                 public boolean onMenuItemClick(MenuItem menuItem) {
+                    if (player == null) return false;
+
                     player.setPlaybackSpeed(playbackSpeed);
                     return true;
                 }
@@ -304,6 +306,8 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
             item.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
                 @Override
                 public boolean onMenuItemClick(MenuItem menuItem) {
+                    if (player == null) return false;
+
                     player.setPlaybackPitch(playbackPitch);
                     return true;
                 }
@@ -317,6 +321,8 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
         remove.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
             @Override
             public boolean onMenuItemClick(MenuItem menuItem) {
+                if (player == null) return false;
+
                 final int index = player.getPlayQueue().indexOf(item);
                 if (index != -1) player.getPlayQueue().remove(index);
                 return true;
@@ -349,7 +355,7 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
 
                 final int sourceIndex = source.getLayoutPosition();
                 final int targetIndex = target.getLayoutPosition();
-                player.getPlayQueue().move(sourceIndex, targetIndex);
+                if (player != null) player.getPlayQueue().move(sourceIndex, targetIndex);
                 return true;
             }
 
@@ -372,11 +378,13 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
         return new PlayQueueItemBuilder.OnSelectedListener() {
             @Override
             public void selected(PlayQueueItem item, View view) {
-                player.onSelected(item);
+                if (player != null) player.onSelected(item);
             }
 
             @Override
             public void held(PlayQueueItem item, View view) {
+                if (player == null) return;
+
                 final int index = player.getPlayQueue().indexOf(item);
                 if (index != -1) buildItemPopupMenu(item, view);
             }
@@ -403,19 +411,19 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
     @Override
     public void onClick(View view) {
         if (view.getId() == repeatButton.getId()) {
-            player.onRepeatClicked();
+            if (player != null) player.onRepeatClicked();
 
         } else if (view.getId() == backwardButton.getId()) {
-            player.onPlayPrevious();
+            if (player != null) player.onPlayPrevious();
 
         } else if (view.getId() == playPauseButton.getId()) {
-            player.onVideoPlayPause();
+            if (player != null) player.onVideoPlayPause();
 
         } else if (view.getId() == forwardButton.getId()) {
-            player.onPlayNext();
+            if (player != null) player.onPlayNext();
 
         } else if (view.getId() == shuffleButton.getId()) {
-            player.onShuffleClicked();
+            if (player != null) player.onShuffleClicked();
 
         } else if (view.getId() == playbackSpeedButton.getId()) {
             playbackSpeedPopupMenu.show();
@@ -450,7 +458,7 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
 
     @Override
     public void onStopTrackingTouch(SeekBar seekBar) {
-        player.simpleExoPlayer.seekTo(seekBar.getProgress());
+        if (player != null) player.simpleExoPlayer.seekTo(seekBar.getProgress());
         seekDisplay.setVisibility(View.GONE);
         seeking = false;
     }

app/src/main/java/org/schabi/newpipe/player/helper/PlayerHelper.java

@@ -12,6 +12,8 @@ import java.text.NumberFormat;
 import java.util.Formatter;
 import java.util.Locale;
 
+import javax.annotation.Nonnull;
+
 public class PlayerHelper {
     private PlayerHelper() {}
 
@@ -56,6 +58,10 @@ public class PlayerHelper {
         return isUsingOldPlayer(context, false);
     }
 
+    public static boolean isRememberingPopupDimensions(@Nonnull final Context context) {
+        return isRememberingPopupDimensions(context, true);
+    }
+
     public static long getPreferredCacheSize(@NonNull final Context context) {
         return 64 * 1024 * 1024L;
     }
@@ -83,6 +89,15 @@ public class PlayerHelper {
     public static boolean isUsingDSP(@NonNull final Context context) {
         return true;
     }
+
+    public static int getShutdownFlingVelocity(@Nonnull final Context context) {
+        return 10000;
+    }
+
+    public static int getTossFlingVelocity(@Nonnull final Context context) {
+        return 2500;
+    }
+
     ////////////////////////////////////////////////////////////////////////////
     // Private helpers
     ////////////////////////////////////////////////////////////////////////////
@@ -103,4 +118,8 @@ public class PlayerHelper {
     private static boolean isUsingOldPlayer(@NonNull final Context context, final boolean b) {
         return getPreferences(context).getBoolean(context.getString(R.string.use_old_player_key), b);
     }
+
+    private static boolean isRememberingPopupDimensions(@Nonnull final Context context, final boolean b) {
+        return getPreferences(context).getBoolean(context.getString(R.string.popup_remember_size_pos_key), b);
+    }
 }

app/src/main/res/values/strings.xml

@@ -122,6 +122,8 @@
     <string name="notification_channel_name">NewPipe Notification</string>
     <string name="notification_channel_description">Notifications for NewPipe Background and Popup Players</string>
 
+    <string name="unknown_content">[Unknown]</string>
+
     <!-- error strings -->
     <string name="general_error">Error</string>
     <string name="network_error">Network error</string>