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每次尝试删除 listView 中的第一项（可见）时，我都需要帮助弄清楚为什么会出现 Null 指针异常。删除其他所有项目都可以正常工作，没有任何错误，但第一个项目一直失败。

这是代码：

private void deleteCurrentItem() {
        ContextualUndoView contextualUndoView = (ContextualUndoView) mDismissView;
        int position = getAbsListView().getPositionForView(contextualUndoView);


        mDeleteItemCallback.deleteItem(position);

    }

详细代码： http: //paste.org/66633

错误日志：

08-10 19:09:22.107: E/AndroidRuntime(973): FATAL EXCEPTION: main
08-10 19:09:22.107: E/AndroidRuntime(973): java.lang.NullPointerException
08-10 19:09:22.107: E/AndroidRuntime(973):  at android.widget.AdapterView.getPositionForView(AdapterView.java:597)
08-10 19:09:22.107: E/AndroidRuntime(973):  at com.haarman.listviewanimations.itemmanipulation.contextualundo.ContextualUndoAdapter$RemoveViewAnimatorListenerAdapter.deleteCurrentItem(ContextualUndoAdapter.java:205)
08-10 19:09:22.107: E/AndroidRuntime(973):  at com.haarman.listviewanimations.itemmanipulation.contextualundo.ContextualUndoAdapter$RemoveViewAnimatorListenerAdapter.onAnimationEnd(ContextualUndoAdapter.java:193)
08-10 19:09:22.107: E/AndroidRuntime(973):  at com.nineoldandroids.animation.ValueAnimator.endAnimation(ValueAnimator.java:1034)
08-10 19:09:22.107: E/AndroidRuntime(973):  at com.nineoldandroids.animation.ValueAnimator.cancel(ValueAnimator.java:968)
08-10 19:09:22.107: E/AndroidRuntime(973):  at com.haarman.listviewanimations.itemmanipulation.contextualundo.ContextualUndoAdapter$RecycleViewListener.onMovedToScrapHeap(ContextualUndoAdapter.java:276)
08-10 19:09:22.107: E/AndroidRuntime(973):  at android.widget.AbsListView$RecycleBin.addScrapView(AbsListView.java:6449)
08-10 19:09:22.107: E/AndroidRuntime(973):  at android.widget.ListView.measureHeightOfChildren(ListView.java:1256)
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1 回答 1

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this line: 

ContextualUndoView contextualUndoView = (ContextualUndoView) mDismissView;

declares your view, but does not instantiate it (so it is null still).

in the next line

int position = getAbsListView().getPositionForView(contextualUndoView);

You try to use your view but it is still null so you get a null pointer.

于 2013-08-11T04:44:17.490 回答