Fix IMS#onPrepareStylusHandwriting call

Ensure onPrepareStylusHandwriting() is always called before
onStartStylusHandwriting().

Test: manually using HandwritingIme
Bug: 217957587
Change-Id: I6f1b8a93a76dbb34d3323439253a3394c05d98a8

core/java/android/inputmethodservice/InkWindow.java

@@ -102,11 +102,4 @@ final class InkWindow extends PhoneWindow {
         lp.token = token;
         setAttributes(lp);
     }
-
-    /**
-     * Returns {@code true} if Window was created and added to WM.
-     */
-    boolean isInitialized() {
-        return mIsViewAdded;
-    }
 }

core/java/android/inputmethodservice/InputMethodService.java

@@ -578,6 +578,7 @@ public class InputMethodService extends AbstractInputMethodService {
     private boolean mImeSurfaceScheduledForRemoval;
     private ImsConfigurationTracker mConfigTracker = new ImsConfigurationTracker();
     private boolean mDestroyed;
+    private boolean mOnPreparedStylusHwCalled;
 
     /** Stylus handwriting Ink window.  */
     private InkWindow mInkWindow;
@@ -919,9 +920,10 @@ public class InputMethodService extends AbstractInputMethodService {
                 Log.d(TAG, "Input should have started before starting Stylus handwriting.");
                 return;
             }
-            if (!mInkWindow.isInitialized()) {
+            if (!mOnPreparedStylusHwCalled) {
                 // prepare hasn't been called by Stylus HOVER.
                 onPrepareStylusHandwriting();
+                mOnPreparedStylusHwCalled = true;
             }
             if (onStartStylusHandwriting()) {
                 mPrivOps.onStylusHandwritingReady(requestId);
@@ -976,6 +978,7 @@ public class InputMethodService extends AbstractInputMethodService {
         public void initInkWindow() {
             mInkWindow.initOnly();
             onPrepareStylusHandwriting();
+            mOnPreparedStylusHwCalled = true;
         }
 
         /**
@@ -2354,7 +2357,7 @@ public class InputMethodService extends AbstractInputMethodService {
 
     /**
      * Called to prepare stylus handwriting.
-     * The system calls this before the first {@link #onStartStylusHandwriting} request.
+     * The system calls this before the {@link #onStartStylusHandwriting} request.
      *
      * <p>Note: The system tries to call this as early as possible, when it detects that
      * handwriting stylus input is imminent. However, that a subsequent call to
@@ -2438,6 +2441,7 @@ public class InputMethodService extends AbstractInputMethodService {
         mInkWindow.hide(false /* remove */);
 
         mPrivOps.finishStylusHandwriting(requestId);
+        mOnPreparedStylusHwCalled = false;
         onFinishStylusHandwriting();
     }