Rub some butter on dictionary list scrolling.

The default implementation for preferences refuses to
cache the views for custom preferences at all. We can
do it, but the system won't do it for us, so this does it.
This makes the screen scrolling smooth again.

Incidentally it also fixes the bug where the button may
not animate on the first element.

Bug: 8882722
Bug: 8883108
Change-Id: I9b2306ac4bf93761a808ebfee3477a65f017cddf

java/src/com/android/inputmethod/dictionarypack/ButtonSwitcher.java

@@ -57,6 +57,11 @@ public class ButtonSwitcher extends FrameLayout {
         super(context, attrs, defStyle);
     }
 
+    public void reset() {
+        mStatus = NOT_INITIALIZED;
+        mAnimateToStatus = NOT_INITIALIZED;
+    }
+
     @Override
     protected void onLayout(final boolean changed, final int left, final int top, final int right,
             final int bottom) {
@@ -64,9 +69,7 @@ public class ButtonSwitcher extends FrameLayout {
         mInstallButton = (Button)findViewById(R.id.dict_install_button);
         mCancelButton = (Button)findViewById(R.id.dict_cancel_button);
         mDeleteButton = (Button)findViewById(R.id.dict_delete_button);
-        mInstallButton.setOnClickListener(mOnClickListener);
+        setInternalOnClickListener(mOnClickListener);
-        mCancelButton.setOnClickListener(mOnClickListener);
-        mDeleteButton.setOnClickListener(mOnClickListener);
         setButtonPositionWithoutAnimation(mStatus);
         if (mAnimateToStatus != NOT_INITIALIZED) {
             // We have been asked to animate before we were ready, so we took a note of it.
@@ -139,6 +142,12 @@ public class ButtonSwitcher extends FrameLayout {
 
     public void setInternalOnClickListener(final OnClickListener listener) {
         mOnClickListener = listener;
+        if (null != mInstallButton) {
+            // Already laid out : do it now
+            mInstallButton.setOnClickListener(mOnClickListener);
+            mCancelButton.setOnClickListener(mOnClickListener);
+            mDeleteButton.setOnClickListener(mOnClickListener);
+        }
     }
 
     private ViewPropertyAnimator animateButton(final View button, final int direction) {

java/src/com/android/inputmethod/dictionarypack/DictionaryListInterfaceState.java

@@ -16,8 +16,11 @@
 
 package com.android.inputmethod.dictionarypack;
 
+import android.view.View;
+
 import com.android.inputmethod.latin.CollectionUtils;
 
+import java.util.ArrayList;
 import java.util.HashMap;
 
 /**
@@ -37,6 +40,7 @@ public class DictionaryListInterfaceState {
     }
 
     private HashMap<String, State> mWordlistToState = CollectionUtils.newHashMap();
+    private ArrayList<View> mViewCache = CollectionUtils.newArrayList();
 
     public boolean isOpen(final String wordlistId) {
         final State state = mWordlistToState.get(wordlistId);
@@ -64,4 +68,16 @@ public class DictionaryListInterfaceState {
             state.mOpen = false;
         }
     }
+
+    public View findFirstOrphanedView() {
+        for (final View v : mViewCache) {
+            if (null == v.getParent()) return v;
+        }
+        return null;
+    }
+
+    public View addToCacheAndReturnView(final View view) {
+        mViewCache.add(view);
+        return view;
+    }
 }

java/src/com/android/inputmethod/dictionarypack/WordListPreference.java

@@ -98,6 +98,14 @@ public final class WordListPreference extends Preference {
         setSummary(getSummary(status));
     }
 
+    @Override
+    public View onCreateView(final ViewGroup parent) {
+        final View orphanedView = mInterfaceState.findFirstOrphanedView();
+        if (null != orphanedView) return orphanedView; // Will be sent to onBindView
+        final View newView = super.onCreateView(parent);
+        return mInterfaceState.addToCacheAndReturnView(newView);
+    }
+
     private String getSummary(final int status) {
         switch (status) {
             // If we are deleting the word list, for the user it's like it's already deleted.
@@ -209,6 +217,9 @@ public final class WordListPreference extends Preference {
 
         final ButtonSwitcher buttonSwitcher =
                 (ButtonSwitcher)view.findViewById(R.id.wordlist_button_switcher);
+        // We need to clear the state of the button switcher, because we reuse views; if we didn't
+        // reset it would animate from whatever its old state was.
+        buttonSwitcher.reset();
         if (mInterfaceState.isOpen(mWordlistId)) {
             // The button is open.
             final int previousStatus = mInterfaceState.getStatus(mWordlistId);