Fix player switching

- Background to popup wasn't asking for permission
- The new task flag is needed to switch from the background/popup UI to the main player

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

@@ -4,6 +4,7 @@ import android.content.Intent;
 import android.view.MenuItem;
 
 import org.schabi.newpipe.R;
+import org.schabi.newpipe.util.PermissionHelper;
 
 import static org.schabi.newpipe.player.BackgroundPlayer.ACTION_CLOSE;
 
@@ -48,6 +49,12 @@ public final class BackgroundPlayerActivity extends ServicePlayerActivity {
     @Override
     public boolean onPlayerOptionSelected(MenuItem item) {
         if (item.getItemId() == R.id.action_switch_popup) {
+
+            if (!PermissionHelper.isPopupEnabled(this)) {
+                PermissionHelper.showPopupEnablementToast(this);
+                return true;
+            }
+
             this.player.setRecovery();
             getApplicationContext().sendBroadcast(getPlayerShutdownIntent());
             getApplicationContext().startService(getSwitchIntent(PopupVideoPlayer.class));

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

@@ -25,7 +25,6 @@ import android.content.Intent;
 import android.content.SharedPreferences;
 import android.content.pm.ActivityInfo;
 import android.content.res.Configuration;
-import android.content.res.Resources;
 import android.graphics.Color;
 import android.media.AudioManager;
 import android.os.Build;
@@ -65,8 +64,6 @@ import org.schabi.newpipe.util.PermissionHelper;
 import org.schabi.newpipe.util.PopupMenuIconHacker;
 import org.schabi.newpipe.util.ThemeHelper;
 
-import java.lang.reflect.Field;
-import java.lang.reflect.Method;
 import java.util.List;
 
 import static org.schabi.newpipe.util.AnimationUtils.animateView;
@@ -400,9 +397,8 @@ public final class MainVideoPlayer extends Activity {
             if (DEBUG) Log.d(TAG, "onFullScreenButtonClicked() called");
             if (simpleExoPlayer == null) return;
 
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M
-                    && !PermissionHelper.checkSystemAlertWindowPermission(MainVideoPlayer.this)) {
-                Toast.makeText(MainVideoPlayer.this, R.string.msg_popup_permission, Toast.LENGTH_LONG).show();
+            if (!PermissionHelper.isPopupEnabled(context)) {
+                PermissionHelper.showPopupEnablementToast(context);
                 return;
             }
 

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

@@ -183,7 +183,7 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
                 this.player.getPlaybackSpeed(),
                 this.player.getPlaybackPitch(),
                 null
-        );
+        ).addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
     }
     ////////////////////////////////////////////////////////////////////////////
     // Service Connection