Switch to listener object instead of ActivityCallThrough

Author: gspencergoog

shell/platform/android/io/flutter/embedding/android/FlutterFragment.java

@@ -12,6 +12,7 @@
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.ViewTreeObserver.OnWindowFocusChangeListener;
 import androidx.activity.OnBackPressedCallback;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -167,6 +168,16 @@ public class FlutterFragment extends Fragment
   protected static final String ARG_SHOULD_AUTOMATICALLY_HANDLE_ON_BACK_PRESSED =
       "should_automatically_handle_on_back_pressed";
 
+  private final OnWindowFocusChangeListener onWindowFocusChangeListener =
+      new OnWindowFocusChangeListener() {
+        @Override
+        public void onWindowFocusChanged(boolean hasFocus) {
+          if (stillAttachedForEvent("onWindowFocusChanged")) {
+            delegate.onWindowFocusChanged(hasFocus);
+          }
+        }
+      };
+
   /**
    * Creates a {@code FlutterFragment} with a default configuration.
    *
@@ -1109,12 +1120,21 @@ public void onStop() {
     }
   }
 
+  @Override
+  public void onViewCreated(View view, Bundle savedInstanceState) {
+    super.onViewCreated(view, savedInstanceState);
+    view.getViewTreeObserver().addOnWindowFocusChangeListener(onWindowFocusChangeListener);
+  }
+
   @Override
   public void onDestroyView() {
     super.onDestroyView();
     if (stillAttachedForEvent("onDestroyView")) {
       delegate.onDestroyView();
     }
+    requireView()
+        .getViewTreeObserver()
+        .removeOnWindowFocusChangeListener(onWindowFocusChangeListener);
   }
 
   @Override
@@ -1235,21 +1255,6 @@ public void onUserLeaveHint() {
     }
   }
 
-  /**
-   * Called when the current {@link android.view.Window} of the {@link android.app.Activity} that
-   * owns this {@link Fragment} gains or loses focus.
-   *
-   * <p>See {@link android.app.Activity#onWindowFocusChanged(boolean)}
-   *
-   * @param hasFocus True if the current window has focus.
-   */
-  @ActivityCallThrough
-  public void onWindowFocusChanged(boolean hasFocus) {
-    if (stillAttachedForEvent("onWindowFocusChanged")) {
-      delegate.onWindowFocusChanged(hasFocus);
-    }
-  }
-
   /**
    * Callback invoked when memory is low.
    *