在 notifyDataSetChanged() 上的 ListViewAnimation insert() NullPointerException

Question

我正在使用 ListViewAnimation 库并尝试为我的 ListView 制作添加项动画。

为了实现这样的动画，他们的文档说我应该这样做：

要使用此功能，只需让您的适配器实现 Insertable，并调用 DynamicListView 上的插入方法之一：

MyInsertableAdapter myAdapter = new MyInsertableAdapter(); // MyInsertableAdapter implements Insertable
mDynamicListView.setAdapter(myAdapter);
mDynamicListView.insert(0, myItem); // myItem is of the type the adapter represents.

这就是我所做的：

1. 我的 Listview 是 DynamicListView（我正在使用 ButterKnife）并将其设置为使用我的适配器

      @InjectView(R.id.flow_list)
       DynamicListView mFlowList;
   
   
       mFlowListAdapter = new FlowListAdapter(getActivity(), mItems);
       mFlowList.setAdapter(mFlowListAdapter);
   

2. 让我的适配器实现“Insertable”接口并覆盖其抽象方法：

   @Override
   public void add(int i, @NonNull Object o) {
       Item newItem = (Item)o;
       mList.add(Item);
       notifyDataSetChanged();
   }
   

3. 在我的 ListView 上调用 insert()

   @OnClick(R.id.done)
   void addItem() {
      ...
       mFlowList.insert(0,item);
   }
   

但是当我运行我的应用程序并单击触发我的 ListView 的 insert() 的完成按钮时，我得到一个 NullPointerException 说：

09-15 11:51:41.046  14660-14660/com.jezer.MyApp E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
        at com.nhaarman.listviewanimations.itemmanipulation.animateaddition.AnimateAdditionAdapter$HeightUpdater.onAnimationUpdate(AnimateAdditionAdapter.java:352)
        at com.nineoldandroids.animation.ValueAnimator.animateValue(ValueAnimator.java:1178)
        at com.nineoldandroids.animation.ValueAnimator.animationFrame(ValueAnimator.java:1139)
        at com.nineoldandroids.animation.ValueAnimator.setCurrentPlayTime(ValueAnimator.java:545)
        at com.nineoldandroids.animation.ValueAnimator.start(ValueAnimator.java:928)
        at com.nineoldandroids.animation.ValueAnimator.start(ValueAnimator.java:951)
        at com.nineoldandroids.animation.AnimatorSet.start(AnimatorSet.java:502)
        at com.nineoldandroids.animation.AnimatorSet.start(AnimatorSet.java:502)
        at com.nhaarman.listviewanimations.itemmanipulation.animateaddition.AnimateAdditionAdapter.getView(AnimateAdditionAdapter.java:318)
        at android.widget.AbsListView.obtainView(AbsListView.java:2232)
        at android.widget.ListView.measureHeightOfChildren(ListView.java:1253)
        at android.widget.ListView.onMeasure(ListView.java:1162)
        at android.view.View.measure(View.java:15775)
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:681)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
        at android.view.View.measure(View.java:15775)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4942)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:15775)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4942)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:15775)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:850)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
        at android.view.View.measure(View.java:15775)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4942)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2193)
        at android.view.View.measure(View.java:15775)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2212)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1291)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1486)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1181)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4942)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:776)
        at android.view.Choreographer.doCallbacks(Choreographer.java:579)
        at android.view.Choreographer.doFrame(Choreographer.java:548)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:762)
        at android.os.Handler.handleCallback(Handler.java:800)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:194)
        at android.app.ActivityThread.main(ActivityThread.java:5391)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:525)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
        at dalvik.system.NativeStart.main(Native Method)

当我在 add() 方法上注释掉 notifyDataSetChanged() 时，我没有收到此异常。然而，这是我知道刷新列表视图并希望看到附加动画的唯一方法。

Answer 1

您是否正在这样做： convertView = inflater.inflate(R.layout.cell, null);

而不是这个？ convertView = inflater.inflate(R.layout.page_cell, parent, false);