Ensure our transparent activity doesn't block touch events to underlying windows

so we won't hold up UI while fetching media info for Add to Playlist or Download actions
lest user might think it freezes when in fact a network request is underway

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

@@ -16,6 +16,7 @@ import android.view.ContextThemeWrapper;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.WindowManager;
 import android.widget.Button;
 import android.widget.RadioButton;
 import android.widget.RadioGroup;
@@ -120,6 +121,14 @@ public class RouterActivity extends AppCompatActivity {
                 ? R.style.RouterActivityThemeLight : R.style.RouterActivityThemeDark);
         Localization.assureCorrectAppLanguage(this);
 
+        // Pass-through touch events to background activities
+        // so that our transparent window won't lock UI in the mean time
+        // network request is underway before showing PlaylistDialog or DownloadDialog
+        // (courtesy of https://stackoverflow.com/a/10606141)
+        getWindow().addFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
+                | WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
+                | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE);
+
         super.onCreate(savedInstanceState);
         Icepick.restoreInstanceState(this, savedInstanceState);