Let SoftInputWindow handle BadTokenException

After several attempts [1][2], this is our latest attempt to
gracefully ignore BadTokenException an IME that is being destroyed is
still handling pending showSoftInput() requests.

The point is that SoftInputWindow is a hidden API. This means that
instead of adding a bunch of try/catch blocks around mWindow.show() in
InputMethodService we can always override SoftInputWindow#show() to
inject our own code around mWindow.show().

With this CL, we can now fully track the internal lifecycle of
SoftInputWindow in SoftInputWindow#mWindowState.  It enables us to
easily sort out cases like double fault cases discussed
in Bug 113159114, where showSoftInput() requests were queued multiple
times and still IMEs crash because what mWindow.show() throws for
the 2nd failure is IllegaStateException not BadTokenException.

 [1] Id1e5f236f48c8ef01b7f157ba3f6e7ab2c26b135
     6fcbb5629019489a88a9748f278d40d554cc5cdc
 [2] I2c21573cf972145ab08e66604cdb9344139a3f31
     e4bbb1cc451c7ebdad9f92968732fc4f6c21a70c

Fix: 113159114
Test: Manually verified IME switching scenario as follows.
  1. Build and flush aosp_taimen-userdebug
  2. make -j SoftKeyboard
  3. adb install -r $OUT/system/app/SoftKeyboard/SoftKeyboard.apk
  4. adb shell ime enable com.example.android.softkeyboard/.SoftKeyboard
  5. Open the Dialer app and tap the top edit field.
  6. Make sure that AOSP Keyboard is shown.
  7. Tap the globe button on AOSP Keyboard.
  8. Make sure that AOSP Keyboard is dismissed and SoftKeybaord is
     shown.
  9. Tap the globe button on SoftKeybaord.
 10. Make sure that SoftKeybaord. is dismissed and AOSP Keyboard is
     shown again.
Test: atest CtsInputMethodTestCases CtsInputMethodServiceHostTestCases
Change-Id: I1f51ed29df6b22b003ca285698e06b8f3ee5106a

1 files changed, 168 insertions, 4 deletions

diff --git a/core/java/android/inputmethodservice/SoftInputWindow.java b/core/java/android/inputmethodservice/SoftInputWindow.java
index 795117e493b6..b4b88871d251 100644
--- a/core/java/android/inputmethodservice/SoftInputWindow.java
+++ b/core/java/android/inputmethodservice/SoftInputWindow.java
@@ -16,15 +16,22 @@
 
 package android.inputmethodservice;
 
+import static java.lang.annotation.RetentionPolicy.SOURCE;
+
+import android.annotation.IntDef;
 import android.app.Dialog;
 import android.content.Context;
 import android.graphics.Rect;
+import android.os.Debug;
 import android.os.IBinder;
+import android.util.Log;
 import android.view.Gravity;
 import android.view.KeyEvent;
 import android.view.MotionEvent;
 import android.view.WindowManager;
 
+import java.lang.annotation.Retention;
+
 /**
  * A SoftInputWindow is a Dialog that is intended to be used for a top-level input
  * method window.  It will be displayed along the edge of the screen, moving
@@ -33,6 +40,9 @@ import android.view.WindowManager;
  * @hide
  */
 public class SoftInputWindow extends Dialog {
+    private static final boolean DEBUG = false;
+    private static final String TAG = "SoftInputWindow";
+
     final String mName;
     final Callback mCallback;
     final KeyEvent.Callback mKeyEventCallback;
@@ -42,16 +52,65 @@ public class SoftInputWindow extends Dialog {
     final boolean mTakesFocus;
     private final Rect mBounds = new Rect();
 
+    @Retention(SOURCE)
+    @IntDef(value = {SoftInputWindowState.TOKEN_PENDING, SoftInputWindowState.TOKEN_SET,
+            SoftInputWindowState.SHOWN_AT_LEAST_ONCE, SoftInputWindowState.REJECTED_AT_LEAST_ONCE})
+    private @interface SoftInputWindowState {
+        /**
+         * The window token is not set yet.
+         */
+        int TOKEN_PENDING = 0;
+        /**
+         * The window token was set, but the window is not shown yet.
+         */
+        int TOKEN_SET = 1;
+        /**
+         * The window was shown at least once.
+         */
+        int SHOWN_AT_LEAST_ONCE = 2;
+        /**
+         * {@link android.view.WindowManager.BadTokenException} was sent when calling
+         * {@link Dialog#show()} at least once.
+         */
+        int REJECTED_AT_LEAST_ONCE = 3;
+        /**
+         * The window is considered destroyed.  Any incoming request should be ignored.
+         */
+        int DESTROYED = 4;
+    }
+
+    @SoftInputWindowState
+    private int mWindowState = SoftInputWindowState.TOKEN_PENDING;
+
     public interface Callback {
         public void onBackPressed();
     }
 
     public void setToken(IBinder token) {
-        WindowManager.LayoutParams lp = getWindow().getAttributes();
-        lp.token = token;
-        getWindow().setAttributes(lp);
+        switch (mWindowState) {
+            case SoftInputWindowState.TOKEN_PENDING:
+                // Normal scenario.  Nothing to worry about.
+                WindowManager.LayoutParams lp = getWindow().getAttributes();
+                lp.token = token;
+                getWindow().setAttributes(lp);
+                updateWindowState(SoftInputWindowState.TOKEN_SET);
+                return;
+            case SoftInputWindowState.TOKEN_SET:
+            case SoftInputWindowState.SHOWN_AT_LEAST_ONCE:
+            case SoftInputWindowState.REJECTED_AT_LEAST_ONCE:
+                throw new IllegalStateException("setToken can be called only once");
+            case SoftInputWindowState.DESTROYED:
+                // Just ignore.  Since there are multiple event queues from the token is issued
+                // in the system server to the timing when it arrives here, it can be delivered
+                // after the is already destroyed.  No one should be blamed because of such an
+                // unfortunate but possible scenario.
+                Log.i(TAG, "Ignoring setToken() because window is already destroyed.");
+                return;
+            default:
+                throw new IllegalStateException("Unexpected state=" + mWindowState);
+        }
     }
-    
+
     /**
      * Create a SoftInputWindow that uses a custom style.
      * 
@@ -190,4 +249,109 @@ public class SoftInputWindow extends Dialog {
 
         getWindow().setFlags(windowSetFlags, windowModFlags);
     }
+
+    @Override
+    public final void show() {
+        switch (mWindowState) {
+            case SoftInputWindowState.TOKEN_PENDING:
+                throw new IllegalStateException("Window token is not set yet.");
+            case SoftInputWindowState.TOKEN_SET:
+            case SoftInputWindowState.SHOWN_AT_LEAST_ONCE:
+                // Normal scenario.  Nothing to worry about.
+                try {
+                    super.show();
+                    updateWindowState(SoftInputWindowState.SHOWN_AT_LEAST_ONCE);
+                } catch (WindowManager.BadTokenException e) {
+                    // Just ignore this exception.  Since show() can be requested from other
+                    // components such as the system and there could be multiple event queues before
+                    // the request finally arrives here, the system may have already invalidated the
+                    // window token attached to our window.  In such a scenario, receiving
+                    // BadTokenException here is an expected behavior.  We just ignore it and update
+                    // the state so that we do not touch this window later.
+                    Log.i(TAG, "Probably the IME window token is already invalidated."
+                            + " show() does nothing.");
+                    updateWindowState(SoftInputWindowState.REJECTED_AT_LEAST_ONCE);
+                }
+                return;
+            case SoftInputWindowState.REJECTED_AT_LEAST_ONCE:
+                // Just ignore.  In general we cannot completely avoid this kind of race condition.
+                Log.i(TAG, "Not trying to call show() because it was already rejected once.");
+                return;
+            case SoftInputWindowState.DESTROYED:
+                // Just ignore.  In general we cannot completely avoid this kind of race condition.
+                Log.i(TAG, "Ignoring show() because the window is already destroyed.");
+                return;
+            default:
+                throw new IllegalStateException("Unexpected state=" + mWindowState);
+        }
+    }
+
+    final void dismissForDestroyIfNecessary() {
+        switch (mWindowState) {
+            case SoftInputWindowState.TOKEN_PENDING:
+            case SoftInputWindowState.TOKEN_SET:
+                // nothing to do because the window has never been shown.
+                updateWindowState(SoftInputWindowState.DESTROYED);
+                return;
+            case SoftInputWindowState.SHOWN_AT_LEAST_ONCE:
+                // Disable exit animation for the current IME window
+                // to avoid the race condition between the exit and enter animations
+                // when the current IME is being switched to another one.
+                try {
+                    getWindow().setWindowAnimations(0);
+                    dismiss();
+                } catch (WindowManager.BadTokenException e) {
+                    // Just ignore this exception.  Since show() can be requested from other
+                    // components such as the system and there could be multiple event queues before
+                    // the request finally arrives here, the system may have already invalidated the
+                    // window token attached to our window.  In such a scenario, receiving
+                    // BadTokenException here is an expected behavior.  We just ignore it and update
+                    // the state so that we do not touch this window later.
+                    Log.i(TAG, "Probably the IME window token is already invalidated. "
+                            + "No need to dismiss it.");
+                }
+                // Either way, consider that the window is destroyed.
+                updateWindowState(SoftInputWindowState.DESTROYED);
+                return;
+            case SoftInputWindowState.REJECTED_AT_LEAST_ONCE:
+                // Just ignore.  In general we cannot completely avoid this kind of race condition.
+                Log.i(TAG,
+                        "Not trying to dismiss the window because it is most likely unnecessary.");
+                // Anyway, consider that the window is destroyed.
+                updateWindowState(SoftInputWindowState.DESTROYED);
+                return;
+            case SoftInputWindowState.DESTROYED:
+                throw new IllegalStateException(
+                        "dismissForDestroyIfNecessary can be called only once");
+            default:
+                throw new IllegalStateException("Unexpected state=" + mWindowState);
+        }
+    }
+
+    private void updateWindowState(@SoftInputWindowState int newState) {
+        if (DEBUG) {
+            if (mWindowState != newState) {
+                Log.d(TAG, "WindowState: " + stateToString(mWindowState) + " -> "
+                        + stateToString(newState) + " @ " + Debug.getCaller());
+            }
+        }
+        mWindowState = newState;
+    }
+
+    private static String stateToString(@SoftInputWindowState int state) {
+        switch (state) {
+            case SoftInputWindowState.TOKEN_PENDING:
+                return "TOKEN_PENDING";
+            case SoftInputWindowState.TOKEN_SET:
+                return "TOKEN_SET";
+            case SoftInputWindowState.SHOWN_AT_LEAST_ONCE:
+                return "SHOWN_AT_LEAST_ONCE";
+            case SoftInputWindowState.REJECTED_AT_LEAST_ONCE:
+                return "REJECTED_AT_LEAST_ONCE";
+            case SoftInputWindowState.DESTROYED:
+                return "DESTROYED";
+            default:
+                throw new IllegalStateException("Unknown state=" + state);
+        }
+    }
 }