Prevent apps from displaying over Settings

Specifically, the DrawOverlayDetails fragment only.

Bug: 36070413
Test: make RunSettingsRoboTests -j100
Change-Id: I0069f0cacf8c963c8c6878dc89a32b205983a568

src/com/android/settings/applications/DrawOverlayDetails.java

@@ -36,6 +36,7 @@ import com.android.internal.logging.nano.MetricsProto.MetricsEvent;
 import com.android.settings.R;
 import com.android.settings.applications.AppStateAppOpsBridge.PermissionState;
 import com.android.settings.applications.AppStateOverlayBridge.OverlayState;
+import com.android.settings.core.TouchOverlayManager;
 import com.android.settings.overlay.FeatureFactory;
 import com.android.settingslib.applications.ApplicationsState.AppEntry;
 
@@ -61,6 +62,8 @@ public class DrawOverlayDetails extends AppInfoWithHeader implements OnPreferenc
     private Intent mSettingsIntent;
     private OverlayState mOverlayState;
 
+    private TouchOverlayManager mTouchOverlayManager;
+
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -68,6 +71,7 @@ public class DrawOverlayDetails extends AppInfoWithHeader implements OnPreferenc
         Context context = getActivity();
         mOverlayBridge = new AppStateOverlayBridge(context, mState, null);
         mAppOpsManager = (AppOpsManager) context.getSystemService(Context.APP_OPS_SERVICE);
+        mTouchOverlayManager = new TouchOverlayManager(context);
 
         // find preferences
         addPreferencesFromResource(R.xml.app_ops_permissions_details);
@@ -89,6 +93,20 @@ public class DrawOverlayDetails extends AppInfoWithHeader implements OnPreferenc
                 .setAction(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
     }
 
+    @Override
+    public void onStart() {
+        super.onStart();
+
+        mTouchOverlayManager.setOverlayAllowed(false);
+    }
+
+    @Override
+    public void onStop() {
+        super.onStop();
+
+        mTouchOverlayManager.setOverlayAllowed(true);
+    }
+
     @Override
     public void onDestroy() {
         super.onDestroy();

src/com/android/settings/core/TouchOverlayManager.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package com.android.settings.core;
+
+import android.app.AppOpsManager;
+import android.content.Context;
+import android.os.Binder;
+import android.os.IBinder;
+
+public class TouchOverlayManager {
+
+    private final Context mContext;
+    private final IBinder mToken = new Binder();
+
+    public TouchOverlayManager(Context context) {
+        mContext = context;
+    }
+
+    public void setOverlayAllowed(boolean allowed) {
+        final AppOpsManager aom = mContext.getSystemService(AppOpsManager.class);
+        if (aom != null) {
+            aom.setUserRestriction(AppOpsManager.OP_SYSTEM_ALERT_WINDOW, !allowed, mToken);
+            aom.setUserRestriction(AppOpsManager.OP_TOAST_WINDOW, !allowed, mToken);
+        }
+    }
+}