Do not allow draw on top for App notification settings

Fixes: 119115683
Test: manual
Change-Id: Ib7b878a23b4a99171c58b5de992fb87feca8a28a

tests/robotests/src/com/android/settings/notification/AppNotificationSettingsTest.java

@@ -0,0 +1,93 @@
+package com.android.settings.notification;
+
+import static android.view.WindowManager.LayoutParams.SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.view.Window;
+import android.view.WindowManager;
+
+import androidx.fragment.app.FragmentActivity;
+import androidx.fragment.app.FragmentManager;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.Robolectric;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+import org.robolectric.annotation.Implementation;
+import org.robolectric.annotation.Implements;
+
+@RunWith(RobolectricTestRunner.class)
+public class AppNotificationSettingsTest {
+
+    private WindowManager.LayoutParams mLayoutParams;
+    private AppNotificationSettings mFragment;
+    private FragmentActivity mActivity;
+    @Mock
+    private Window mWindow;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mLayoutParams = new WindowManager.LayoutParams();
+        mActivity = spy(Robolectric.setupActivity(FragmentActivity.class));
+        mFragment = spy(new AppNotificationSettings());
+        when(mFragment.getActivity()).thenReturn(mActivity);
+        when(mFragment.getFragmentManager()).thenReturn(mock(FragmentManager.class));
+        when(mActivity.getWindow()).thenReturn(mWindow);
+        when(mWindow.getAttributes()).thenReturn(mLayoutParams);
+    }
+
+    @Test
+    @Config(shadows = {ShadowNotificationSettingsBase.class})
+    public void onResume_shouldHideSystemOverlay() {
+        mFragment.onResume();
+
+        verify(mWindow).addSystemFlags(SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS);
+    }
+
+    @Test
+    @Config(shadows = {ShadowNotificationSettingsBase.class})
+    public void onPause_shouldRemoveHideSystemOverlay() {
+        mFragment.onResume();
+
+        verify(mWindow).addSystemFlags(SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS);
+
+        mFragment.onPause();
+
+        // There's no Window.clearPrivateFlags() method, so the Window.attributes are updated.
+        ArgumentCaptor<WindowManager.LayoutParams> paramCaptor = ArgumentCaptor.forClass(
+                WindowManager.LayoutParams.class);
+        verify(mWindow).setAttributes(paramCaptor.capture());
+        assertEquals(0,
+                paramCaptor.getValue().privateFlags
+                        & SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS);
+    }
+
+    @Implements(NotificationSettingsBase.class)
+    public static class ShadowNotificationSettingsBase {
+
+        protected void __constructor__() {
+            // Do nothing
+        }
+
+        @Implementation
+        protected void onResume() {
+            // No-op.
+        }
+
+        @Implementation
+        protected void onPause() {
+            // No-op.
+        }
+    }
+}