Merge "Prevent apps to overlay other apps via toast windows" into nyc-mr1-dev

core/java/android/app/ITransientNotification.aidl

@@ -19,7 +19,7 @@ package android.app;
 
 /** @hide */
 oneway interface ITransientNotification {
-    void show();
+    void show(IBinder windowToken);
     void hide();
 }
 

core/java/android/view/SurfaceView.java

@@ -227,6 +227,7 @@ public class SurfaceView extends View {
         mSession = getWindowSession();
         mLayout.token = getWindowToken();
         mLayout.setTitle("SurfaceView - " + getViewRootImpl().getTitle());
+        mLayout.packageName = mContext.getOpPackageName();
         mViewVisibility = getVisibility() == VISIBLE;
 
         if (!mGlobalListenersAdded) {

core/java/android/view/WindowManager.java

@@ -1752,14 +1752,18 @@ public interface WindowManager extends ViewManager {
         public CharSequence accessibilityTitle;
 
         /**
-         * Sets a timeout in milliseconds before which the window will be removed
+         * Sets a timeout in milliseconds before which the window will be hidden
          * by the window manager. Useful for transient notifications like toasts
          * so we don't have to rely on client cooperation to ensure the window
-         * is removed. Must be specified at window creation time.
+         * is hidden. Must be specified at window creation time. Note that apps
+         * are not prepared to handle their windows being removed without their
+         * explicit request and may try to interact with the removed window
+         * resulting in undefined behavior and crashes. Therefore, we do hide
+         * such windows to prevent them from overlaying other apps.
          *
          * @hide
          */
-        public long removeTimeoutMilliseconds = -1;
+        public long hideTimeoutMilliseconds = -1;
 
         public LayoutParams() {
             super(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
@@ -1895,7 +1899,7 @@ public interface WindowManager extends ViewManager {
             out.writeInt(needsMenuKey);
             out.writeInt(accessibilityIdOfAnchor);
             TextUtils.writeToParcel(accessibilityTitle, out, parcelableFlags);
-            out.writeLong(removeTimeoutMilliseconds);
+            out.writeLong(hideTimeoutMilliseconds);
         }
 
         public static final Parcelable.Creator<LayoutParams> CREATOR
@@ -1949,7 +1953,7 @@ public interface WindowManager extends ViewManager {
             needsMenuKey = in.readInt();
             accessibilityIdOfAnchor = in.readInt();
             accessibilityTitle = TextUtils.CHAR_SEQUENCE_CREATOR.createFromParcel(in);
-            removeTimeoutMilliseconds = in.readLong();
+            hideTimeoutMilliseconds = in.readLong();
         }
 
         @SuppressWarnings({"PointlessBitwiseExpression"})
@@ -2171,7 +2175,7 @@ public interface WindowManager extends ViewManager {
             }
 
             // This can't change, it's only set at window creation time.
-            removeTimeoutMilliseconds = o.removeTimeoutMilliseconds;
+            hideTimeoutMilliseconds = o.hideTimeoutMilliseconds;
 
             return changes;
         }

core/java/android/widget/Toast.java

@@ -25,6 +25,8 @@ import android.content.res.Configuration;
 import android.content.res.Resources;
 import android.graphics.PixelFormat;
 import android.os.Handler;
+import android.os.IBinder;
+import android.os.Message;
 import android.os.RemoteException;
 import android.os.ServiceManager;
 import android.util.Log;
@@ -326,13 +328,6 @@ public class Toast {
     }
 
     private static class TN extends ITransientNotification.Stub {
-        final Runnable mShow = new Runnable() {
-            @Override
-            public void run() {
-                handleShow();
-            }
-        };
-
         final Runnable mHide = new Runnable() {
             @Override
             public void run() {
@@ -343,7 +338,13 @@ public class Toast {
         };
 
         private final WindowManager.LayoutParams mParams = new WindowManager.LayoutParams();
-        final Handler mHandler = new Handler();
+        final Handler mHandler = new Handler() {
+            @Override
+            public void handleMessage(Message msg) {
+                IBinder token = (IBinder) msg.obj;
+                handleShow(token);
+            }
+        };
 
         int mGravity;
         int mX, mY;
@@ -379,9 +380,9 @@ public class Toast {
          * schedule handleShow into the right thread
          */
         @Override
-        public void show() {
+        public void show(IBinder windowToken) {
             if (localLOGV) Log.v(TAG, "SHOW: " + this);
-            mHandler.post(mShow);
+            mHandler.obtainMessage(0, windowToken).sendToTarget();
         }
 
         /**
@@ -393,7 +394,7 @@ public class Toast {
             mHandler.post(mHide);
         }
 
-        public void handleShow() {
+        public void handleShow(IBinder windowToken) {
             if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView
                     + " mNextView=" + mNextView);
             if (mView != mNextView) {
@@ -422,8 +423,9 @@ public class Toast {
                 mParams.verticalMargin = mVerticalMargin;
                 mParams.horizontalMargin = mHorizontalMargin;
                 mParams.packageName = packageName;
-                mParams.removeTimeoutMilliseconds = mDuration ==
+                mParams.hideTimeoutMilliseconds = mDuration ==
                     Toast.LENGTH_LONG ? LONG_DURATION_TIMEOUT : SHORT_DURATION_TIMEOUT;
+                mParams.token = windowToken;
                 if (mView.getParent() != null) {
                     if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);
                     mWM.removeView(mView);

services/core/java/com/android/server/notification/NotificationManagerService.java

@@ -58,7 +58,6 @@ import android.app.Notification;
 import android.app.NotificationManager;
 import android.app.NotificationManager.Policy;
 import android.app.PendingIntent;
-import android.app.RemoteInput;
 import android.app.StatusBarManager;
 import android.app.backup.BackupManager;
 import android.app.usage.UsageEvents;
@@ -93,7 +92,6 @@ import android.os.IBinder;
 import android.os.IInterface;
 import android.os.Looper;
 import android.os.Message;
-import android.os.Parcelable;
 import android.os.Process;
 import android.os.RemoteException;
 import android.os.SystemClock;
@@ -122,6 +120,8 @@ import android.util.Log;
 import android.util.Slog;
 import android.util.SparseArray;
 import android.util.Xml;
+import android.view.WindowManager;
+import android.view.WindowManagerInternal;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityManager;
 import android.widget.Toast;
@@ -138,6 +138,7 @@ import com.android.server.SystemService;
 import com.android.server.lights.Light;
 import com.android.server.lights.LightsManager;
 import com.android.server.notification.ManagedServices.ManagedServiceInfo;
+import com.android.server.policy.PhoneWindowManager;
 import com.android.server.statusbar.StatusBarManagerInternal;
 import com.android.server.vr.VrManagerInternal;
 import com.android.server.notification.ManagedServices.UserProfiles;
@@ -193,7 +194,7 @@ public class NotificationManagerService extends SystemService {
     private static final int MESSAGE_RECONSIDER_RANKING = 1000;
     private static final int MESSAGE_RANKING_SORT = 1001;
 
-    static final int LONG_DELAY = 3500; // 3.5 seconds
+    static final int LONG_DELAY = PhoneWindowManager.TOAST_WINDOW_TIMEOUT;
     static final int SHORT_DELAY = 2000; // 2 seconds
 
     static final long[] DEFAULT_VIBRATE_PATTERN = {0, 250, 250, 250};
@@ -232,6 +233,7 @@ public class NotificationManagerService extends SystemService {
     @Nullable StatusBarManagerInternal mStatusBar;
     Vibrator mVibrator;
     private VrManagerInternal mVrManagerInternal;
+    private WindowManagerInternal mWindowManagerInternal;
 
     final IBinder mForegroundToken = new Binder();
     private Handler mHandler;
@@ -452,13 +454,15 @@ public class NotificationManagerService extends SystemService {
         final String pkg;
         final ITransientNotification callback;
         int duration;
+        Binder token;
 
-        ToastRecord(int pid, String pkg, ITransientNotification callback, int duration)
+        ToastRecord(int pid, String pkg, ITransientNotification callback, int duration,
-        {
+                    Binder token) {
             this.pid = pid;
             this.pkg = pkg;
             this.callback = callback;
             this.duration = duration;
+            this.token = token;
         }
 
         void update(int duration) {
@@ -1125,6 +1129,7 @@ public class NotificationManagerService extends SystemService {
             mAudioManager = (AudioManager) getContext().getSystemService(Context.AUDIO_SERVICE);
             mAudioManagerInternal = getLocalService(AudioManagerInternal.class);
             mVrManagerInternal = getLocalService(VrManagerInternal.class);
+            mWindowManagerInternal = LocalServices.getService(WindowManagerInternal.class);
             mZenModeHelper.onSystemReady();
         } else if (phase == SystemService.PHASE_THIRD_PARTY_APPS_CAN_START) {
             // This observer will force an update when observe is called, causing us to
@@ -1325,10 +1330,13 @@ public class NotificationManagerService extends SystemService {
                             }
                         }
 
-                        record = new ToastRecord(callingPid, pkg, callback, duration);
+                        Binder token = new Binder();
+                        mWindowManagerInternal.addWindowToken(token,
+                                WindowManager.LayoutParams.TYPE_TOAST);
+                        record = new ToastRecord(callingPid, pkg, callback, duration, token);
                         mToastQueue.add(record);
                         index = mToastQueue.size() - 1;
-                        keepProcessAliveLocked(callingPid);
+                        keepProcessAliveIfNeededLocked(callingPid);
                     }
                     // If it's at index 0, it's the current toast.  It doesn't matter if it's
                     // new or just been updated.  Call back and tell it to show itself.
@@ -2991,7 +2999,7 @@ public class NotificationManagerService extends SystemService {
         while (record != null) {
             if (DBG) Slog.d(TAG, "Show pkg=" + record.pkg + " callback=" + record.callback);
             try {
-                record.callback.show();
+                record.callback.show(record.token);
                 scheduleTimeoutLocked(record);
                 return;
             } catch (RemoteException e) {
@@ -3002,7 +3010,7 @@ public class NotificationManagerService extends SystemService {
                 if (index >= 0) {
                     mToastQueue.remove(index);
                 }
-                keepProcessAliveLocked(record.pid);
+                keepProcessAliveIfNeededLocked(record.pid);
                 if (mToastQueue.size() > 0) {
                     record = mToastQueue.get(0);
                 } else {
@@ -3022,8 +3030,11 @@ public class NotificationManagerService extends SystemService {
             // don't worry about this, we're about to remove it from
             // the list anyway
         }
-        mToastQueue.remove(index);
+
-        keepProcessAliveLocked(record.pid);
+        ToastRecord lastToast = mToastQueue.remove(index);
+        mWindowManagerInternal.removeWindowToken(lastToast.token, true);
+
+        keepProcessAliveIfNeededLocked(record.pid);
         if (mToastQueue.size() > 0) {
             // Show the next one. If the callback fails, this will remove
             // it from the list, so don't assume that the list hasn't changed
@@ -3067,7 +3078,7 @@ public class NotificationManagerService extends SystemService {
     }
 
     // lock on mToastQueue
-    void keepProcessAliveLocked(int pid)
+    void keepProcessAliveIfNeededLocked(int pid)
     {
         int toastCount = 0; // toasts from this pid
         ArrayList<ToastRecord> list = mToastQueue;

services/core/java/com/android/server/policy/PhoneWindowManager.java

@@ -301,6 +301,9 @@ public class PhoneWindowManager implements WindowManagerPolicy {
     /** Amount of time (in milliseconds) to wait for windows drawn before powering on. */
     static final int WAITING_FOR_DRAWN_TIMEOUT = 1000;
 
+    /** Amount of time (in milliseconds) a toast window can be shown. */
+    public static final int TOAST_WINDOW_TIMEOUT = 3500; // 3.5 seconds
+
     /**
      * Lock protecting internal state.  Must not call out into window
      * manager with lock held.  (This lock will be acquired in places
@@ -2229,9 +2232,22 @@ public class PhoneWindowManager implements WindowManagerPolicy {
                     attrs.privateFlags &= ~WindowManager.LayoutParams.PRIVATE_FLAG_KEYGUARD;
                 }
                 break;
+
             case TYPE_SCREENSHOT:
                 attrs.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
                 break;
+
+            case TYPE_TOAST:
+                // While apps should use the dedicated toast APIs to add such windows
+                // it possible legacy apps to add the window directly. Therefore, we
+                // make windows added directly by the app behave as a toast as much
+                // as possible in terms of timeout and animation.
+                if (attrs.hideTimeoutMilliseconds < 0
+                        || attrs.hideTimeoutMilliseconds > TOAST_WINDOW_TIMEOUT) {
+                    attrs.hideTimeoutMilliseconds = TOAST_WINDOW_TIMEOUT;
+                }
+                attrs.windowAnimations = com.android.internal.R.style.Animation_Toast;
+                break;
         }
 
         if (attrs.type != TYPE_STATUS_BAR) {

services/core/java/com/android/server/wm/DisplayContent.java

@@ -22,14 +22,19 @@ import static android.app.ActivityManager.StackId.PINNED_STACK_ID;
 import static android.view.WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
 import static android.view.WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;
 import static android.view.WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL;
+import static android.view.WindowManager.LayoutParams.TYPE_TOAST;
 import static com.android.server.wm.WindowManagerDebugConfig.DEBUG_VISIBILITY;
 import static com.android.server.wm.WindowManagerDebugConfig.TAG_WM;
 import static com.android.server.wm.WindowState.RESIZE_HANDLE_WIDTH_IN_DP;
 
 import android.app.ActivityManager.StackId;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
 import android.graphics.Rect;
 import android.graphics.Region;
 import android.graphics.Region.Op;
+import android.os.Build;
+import android.os.UserHandle;
 import android.util.DisplayMetrics;
 import android.util.Slog;
 import android.view.Display;
@@ -684,4 +689,39 @@ class DisplayContent {
             mStacks.get(i).overridePlayingAppAnimations(a);
         }
     }
+
+    boolean canAddToastWindowForUid(int uid) {
+        // We allow one toast window per UID being shown at a time.
+        WindowList windows = getWindowList();
+        final int windowCount = windows.size();
+        for (int i = 0; i < windowCount; i++) {
+            WindowState window = windows.get(i);
+            if (window.mAttrs.type == TYPE_TOAST && window.mOwnerUid == uid
+                    && !window.mPermanentlyHidden && !window.mAnimatingExit) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    void scheduleToastWindowsTimeoutIfNeededLocked(WindowState oldFocus,
+                                                   WindowState newFocus) {
+        if (oldFocus == null || (newFocus != null && newFocus.mOwnerUid == oldFocus.mOwnerUid)) {
+            return;
+        }
+        final int lostFocusUid = oldFocus.mOwnerUid;
+        WindowList windows = getWindowList();
+        final int windowCount = windows.size();
+        for (int i = 0; i < windowCount; i++) {
+            WindowState window = windows.get(i);
+            if (window.mAttrs.type == TYPE_TOAST && window.mOwnerUid == lostFocusUid) {
+                if (!mService.mH.hasMessages(WindowManagerService.H.WINDOW_HIDE_TIMEOUT, window)) {
+                    mService.mH.sendMessageDelayed(
+                            mService.mH.obtainMessage(
+                                    WindowManagerService.H.WINDOW_HIDE_TIMEOUT, window),
+                            window.mAttrs.hideTimeoutMilliseconds);
+                }
+            }
+        }
+    }
 }

services/core/java/com/android/server/wm/WindowManagerService.java

@@ -35,6 +35,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.pm.ActivityInfo;
+import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
 import android.content.res.CompatibilityInfo;
 import android.content.res.Configuration;
@@ -201,6 +202,7 @@ import static android.view.WindowManager.LayoutParams.TYPE_NAVIGATION_BAR;
 import static android.view.WindowManager.LayoutParams.TYPE_PRIVATE_PRESENTATION;
 import static android.view.WindowManager.LayoutParams.TYPE_QS_DIALOG;
 import static android.view.WindowManager.LayoutParams.TYPE_STATUS_BAR;
+import static android.view.WindowManager.LayoutParams.TYPE_TOAST;
 import static android.view.WindowManager.LayoutParams.TYPE_VOICE_INTERACTION;
 import static android.view.WindowManager.LayoutParams.TYPE_WALLPAPER;
 import static android.view.WindowManagerGlobal.RELAYOUT_DEFER_SURFACE_DESTROY;
@@ -1869,6 +1871,7 @@ public class WindowManagerService extends IWindowManager.Stub
         boolean reportNewConfig = false;
         WindowState attachedWindow = null;
         long origId;
+        final int callingUid = Binder.getCallingUid();
         final int type = attrs.type;
 
         synchronized(mWindowMap) {
@@ -1916,6 +1919,8 @@ public class WindowManagerService extends IWindowManager.Stub
             boolean addToken = false;
             WindowToken token = mTokenMap.get(attrs.token);
             AppWindowToken atoken = null;
+            boolean addToastWindowRequiresToken = false;
+
             if (token == null) {
                 if (type >= FIRST_APPLICATION_WINDOW && type <= LAST_APPLICATION_WINDOW) {
                     Slog.w(TAG_WM, "Attempted to add application window with unknown token "
@@ -1952,6 +1957,15 @@ public class WindowManagerService extends IWindowManager.Stub
                             + attrs.token + ".  Aborting.");
                     return WindowManagerGlobal.ADD_BAD_APP_TOKEN;
                 }
+                if (type == TYPE_TOAST) {
+                    // Apps targeting SDK above N MR1 cannot arbitrary add toast windows.
+                    if (doesAddToastWindowRequireToken(attrs.packageName, callingUid,
+                            attachedWindow)) {
+                        Slog.w(TAG_WM, "Attempted to add a toast window with unknown token "
+                                + attrs.token + ".  Aborting.");
+                        return WindowManagerGlobal.ADD_BAD_APP_TOKEN;
+                    }
+                }
                 token = new WindowToken(this, attrs.token, -1, false);
                 addToken = true;
             } else if (type >= FIRST_APPLICATION_WINDOW && type <= LAST_APPLICATION_WINDOW) {
@@ -2001,6 +2015,15 @@ public class WindowManagerService extends IWindowManager.Stub
                             + attrs.token + ".  Aborting.");
                     return WindowManagerGlobal.ADD_BAD_APP_TOKEN;
                 }
+            } else if (type == TYPE_TOAST) {
+                // Apps targeting SDK above N MR1 cannot arbitrary add toast windows.
+                addToastWindowRequiresToken = doesAddToastWindowRequireToken(attrs.packageName,
+                        callingUid, attachedWindow);
+                if (addToastWindowRequiresToken && token.windowType != TYPE_TOAST) {
+                    Slog.w(TAG_WM, "Attempted to add a toast window with bad token "
+                            + attrs.token + ".  Aborting.");
+                    return WindowManagerGlobal.ADD_BAD_APP_TOKEN;
+                }
             } else if (type == TYPE_QS_DIALOG) {
                 if (token.windowType != TYPE_QS_DIALOG) {
                     Slog.w(TAG_WM, "Attempted to add QS dialog window with bad token "
@@ -2045,6 +2068,36 @@ public class WindowManagerService extends IWindowManager.Stub
                 win.openInputChannel(outInputChannel);
             }
 
+            // If adding a toast requires a token for this app we always schedule hiding
+            // toast windows to make sure they don't stick around longer then necessary.
+            // We hide instead of remove such windows as apps aren't prepared to handle
+            // windows being removed under them.
+            //
+            // If the app is older it can add toasts without a token and hence overlay
+            // other apps. To be maximally compatible with these apps we will hide the
+            // window after the toast timeout only if the focused window is from another
+            // UID, otherwise we allow unlimited duration. When a UID looses focus we
+            // schedule hiding all of its toast windows.
+            if (type == TYPE_TOAST) {
+                if (!getDefaultDisplayContentLocked().canAddToastWindowForUid(callingUid)) {
+                    Slog.w(TAG_WM, "Adding more than one toast window for UID at a time.");
+                    return WindowManagerGlobal.ADD_DUPLICATE_ADD;
+                }
+                // Make sure this happens before we moved focus as one can make the
+                // toast focusable to force it not being hidden after the timeout.
+                // Focusable toasts are always timed out to prevent a focused app to
+                // show a focusable toasts while it has focus which will be kept on
+                // the screen after the activity goes away.
+                if (addToastWindowRequiresToken
+                        || (attrs.flags & LayoutParams.FLAG_NOT_FOCUSABLE) == 0
+                        || mCurrentFocus == null
+                        || mCurrentFocus.mOwnerUid != callingUid) {
+                    mH.sendMessageDelayed(
+                            mH.obtainMessage(H.WINDOW_HIDE_TIMEOUT, win),
+                            win.mAttrs.hideTimeoutMilliseconds);
+                }
+            }
+
             // From now on, no exceptions or errors allowed!
 
             res = WindowManagerGlobal.ADD_OKAY;
@@ -2183,11 +2236,6 @@ public class WindowManagerService extends IWindowManager.Stub
             if (win.isVisibleOrAdding() && updateOrientationFromAppTokensLocked(false)) {
                 reportNewConfig = true;
             }
-            if (attrs.removeTimeoutMilliseconds > 0) {
-                mH.sendMessageDelayed(
-                        mH.obtainMessage(H.WINDOW_REMOVE_TIMEOUT, win),
-                        attrs.removeTimeoutMilliseconds);
-            }
         }
 
         if (reportNewConfig) {
@@ -2199,6 +2247,32 @@ public class WindowManagerService extends IWindowManager.Stub
         return res;
     }
 
+    private boolean doesAddToastWindowRequireToken(String packageName, int callingUid,
+            WindowState attachedWindow) {
+        // Try using the target SDK of the root window
+        if (attachedWindow != null) {
+            return attachedWindow.mAppToken != null
+                    && attachedWindow.mAppToken.targetSdk > Build.VERSION_CODES.N_MR1;
+        } else {
+            // Otherwise, look at the package
+            try {
+                ApplicationInfo appInfo = mContext.getPackageManager()
+                        .getApplicationInfoAsUser(packageName, 0,
+                                UserHandle.getUserId(callingUid));
+                if (appInfo.uid != callingUid) {
+                    throw new SecurityException("Package " + packageName + " not in UID "
+                            + callingUid);
+                }
+                if (appInfo.targetSdkVersion > Build.VERSION_CODES.N_MR1) {
+                    return true;
+                }
+            } catch (PackageManager.NameNotFoundException e) {
+                /* ignore */
+            }
+        }
+        return false;
+    }
+
     /**
      * Returns true if we're done setting up any transitions.
      */
@@ -8165,7 +8239,7 @@ public class WindowManagerService extends IWindowManager.Stub
         public static final int NOTIFY_APP_TRANSITION_FINISHED = 49;
         public static final int NOTIFY_STARTING_WINDOW_DRAWN = 50;
         public static final int UPDATE_ANIMATION_SCALE = 51;
-        public static final int WINDOW_REMOVE_TIMEOUT = 52;
+        public static final int WINDOW_HIDE_TIMEOUT = 52;
         public static final int NOTIFY_DOCKED_STACK_MINIMIZED_CHANGED = 53;
         public static final int SEAMLESS_ROTATION_TIMEOUT = 54;
 
@@ -8785,7 +8859,7 @@ public class WindowManagerService extends IWindowManager.Stub
                     mAmInternal.notifyStartingWindowDrawn();
                 }
                 break;
-                case WINDOW_REMOVE_TIMEOUT: {
+                case WINDOW_HIDE_TIMEOUT: {
                     final WindowState window = (WindowState) msg.obj;
                     synchronized(mWindowMap) {
                         // TODO: This is all about fixing b/21693547
@@ -8796,8 +8870,11 @@ public class WindowManagerService extends IWindowManager.Stub
                         // running under debugger) to crash (b/29105388). The windows will
                         // eventually be removed when the client process finishes.
                         // The best we can do for now is remove the FLAG_KEEP_SCREEN_ON
-                        // and prevent the symptoms of b/21693547.
+                        // and prevent the symptoms of b/21693547. Since apps don't
+                        // support windows being removed under them we hide the window
+                        // and it will be removed when the app dies.
                         window.mAttrs.flags &= ~FLAG_KEEP_SCREEN_ON;
+                        window.hidePermanentlyLw();
                         window.setDisplayLayoutNeeded();
                         mWindowPlacerLocked.performSurfacePlacement();
                     }
@@ -9833,6 +9910,12 @@ public class WindowManagerService extends IWindowManager.Stub
 
             adjustForImeIfNeeded(displayContent);
 
+            // We may need to schedule some toast windows to be removed. The
+            // toasts for an app that does not have input focus are removed
+            // within a timeout to prevent apps to redress other apps' UI.
+            oldFocus.getDisplayContent().scheduleToastWindowsTimeoutIfNeededLocked(
+                    oldFocus, newFocus);
+
             Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
             return true;
         }

services/core/java/com/android/server/wm/WindowState.java

@@ -166,6 +166,7 @@ final class WindowState implements WindowManagerPolicy.WindowState {
     boolean mPolicyVisibility = true;
     boolean mPolicyVisibilityAfterAnim = true;
     boolean mAppOpVisibility = true;
+    boolean mPermanentlyHidden; // the window should never be shown again
     boolean mAppFreezing;
     boolean mAttachedHidden;    // is our parent window hidden?
     boolean mWallpaperVisible;  // for wallpaper, what was last vis report?
@@ -1876,6 +1877,11 @@ final class WindowState implements WindowManagerPolicy.WindowState {
             // Being hidden due to app op request.
             return false;
         }
+        if (mPermanentlyHidden) {
+            // Permanently hidden until the app exists as apps aren't prepared
+            // to handle their windows being removed from under them.
+            return false;
+        }
         if (mPolicyVisibility && mPolicyVisibilityAfterAnim) {
             // Already showing.
             return false;
@@ -1966,6 +1972,13 @@ final class WindowState implements WindowManagerPolicy.WindowState {
         }
     }
 
+    public void hidePermanentlyLw() {
+        if (!mPermanentlyHidden) {
+            mPermanentlyHidden = true;
+            hideLw(true, true);
+        }
+    }
+
     public void pokeDrawLockLw(long timeout) {
         if (isVisibleOrAdding()) {
             if (mDrawLock == null) {
@@ -2615,7 +2628,7 @@ final class WindowState implements WindowManagerPolicy.WindowState {
             pw.println(Integer.toHexString(mSystemUiVisibility));
         }
         if (!mPolicyVisibility || !mPolicyVisibilityAfterAnim || !mAppOpVisibility
-                || mAttachedHidden) {
+                || mAttachedHidden || mPermanentlyHidden) {
             pw.print(prefix); pw.print("mPolicyVisibility=");
                     pw.print(mPolicyVisibility);
                     pw.print(" mPolicyVisibilityAfterAnim=");
@@ -2623,6 +2636,7 @@ final class WindowState implements WindowManagerPolicy.WindowState {
                     pw.print(" mAppOpVisibility=");
                     pw.print(mAppOpVisibility);
                     pw.print(" mAttachedHidden="); pw.println(mAttachedHidden);
+                    pw.print(" mPermanentlyHidden="); pw.println(mPermanentlyHidden);
         }
         if (!mRelayoutCalled || mLayoutNeeded) {
             pw.print(prefix); pw.print("mRelayoutCalled="); pw.print(mRelayoutCalled);