Migrate PopupWindow to use OnBackInvokedDispatcher

Bug: 219968356
Test: In BackTestApp, show popup window and swipe back to close it.
Test: CTS: android.widget.cts.BackInvokedOnWidgetsTest#popupWindowDismissedOnBackGesture
Change-Id: Ic22c12e2ed9f1c961f6e0abfdaf3d2a9a7bd2934

core/java/android/widget/PopupWindow.java

@@ -56,6 +56,9 @@ import android.view.WindowManager;
 import android.view.WindowManager.LayoutParams;
 import android.view.WindowManager.LayoutParams.SoftInputModeFlags;
 import android.view.WindowManagerGlobal;
+import android.window.OnBackInvokedCallback;
+import android.window.OnBackInvokedDispatcher;
+import android.window.WindowOnBackInvokedDispatcher;
 
 import com.android.internal.R;
 
@@ -277,6 +280,8 @@ public class PopupWindow {
 
     private boolean mPopupViewInitialLayoutDirectionInherited;
 
+    private OnBackInvokedCallback mBackCallback;
+
     /**
      * <p>Create a new empty, non focusable popup window of dimension (0,0).</p>
      *
@@ -2028,6 +2033,8 @@ public class PopupWindow {
         final PopupDecorView decorView = mDecorView;
         final View contentView = mContentView;
 
+        unregisterBackCallback(decorView.findOnBackInvokedDispatcher());
+
         final ViewGroup contentHolder;
         final ViewParent contentParent = contentView.getParent();
         if (contentParent instanceof ViewGroup) {
@@ -2082,6 +2089,15 @@ public class PopupWindow {
         }
     }
 
+    private void unregisterBackCallback(@Nullable OnBackInvokedDispatcher onBackInvokedDispatcher) {
+        OnBackInvokedCallback backCallback = mBackCallback;
+        mBackCallback = null;
+        if (onBackInvokedDispatcher != null && backCallback != null) {
+            onBackInvokedDispatcher.unregisterOnBackInvokedCallback(
+                    backCallback);
+        }
+    }
+
     /**
      * Returns the window-relative epicenter bounds to be used by enter and
      * exit transitions.
@@ -2725,6 +2741,30 @@ public class PopupWindow {
                 }
             }
         }
+
+        @Override
+        protected void onAttachedToWindow() {
+            super.onAttachedToWindow();
+            if (!WindowOnBackInvokedDispatcher.isOnBackInvokedCallbackEnabled(mContext)) {
+                return;
+            }
+
+            OnBackInvokedDispatcher dispatcher = findOnBackInvokedDispatcher();
+            if (dispatcher == null) {
+                return;
+            }
+
+            mBackCallback = PopupWindow.this::dismiss;
+
+            dispatcher.registerOnBackInvokedCallback(OnBackInvokedDispatcher.PRIORITY_DEFAULT,
+                    mBackCallback);
+        }
+
+        @Override
+        protected void onDetachedFromWindow() {
+            super.onDetachedFromWindow();
+            unregisterBackCallback(findOnBackInvokedDispatcher());
+        }
     }
 
     private class PopupBackgroundView extends FrameLayout {