Fix Qt bootstrap non-back key handling

Author: lanmao

pythonforandroid/bootstraps/qt/build/src/main/java/org/kivy/android/PythonActivity.java

@@ -123,8 +123,10 @@ public void onDestroy() {
 
     @Override
     public boolean onKeyDown(int keyCode, KeyEvent event) {
-        // If it wasn't the Back key or there's no web page history, bubble up to the default
-        // system behavior (probably exit the activity)
+        if (keyCode != KeyEvent.KEYCODE_BACK) {
+            return super.onKeyDown(keyCode, event);
+        }
+
         if (SystemClock.elapsedRealtime() - lastBackClick > 2000) {
             lastBackClick = SystemClock.elapsedRealtime();
             Toast.makeText(this, "Click again to close the app", Toast.LENGTH_LONG).show();