Java Android GridView获取子项don'；行不通

我想获取GridView子项，我使用下面的代码，但它不起作用

    mAppGridAdapter = new gridadapter(mContext, appPackageInfos);
    mAppManaGridView.setAdapter(mAppGridAdapter);

    if(mAppManaGridView.getCount()>0)
    {                                                                       
        mAppManaGridView.setSelection(0);
        Log.d("adan", "adan>" + mAppManaGridView.getCount());
        Log.d("adan", mAppManaGridView.getFirstVisiblePosition()  +  ",  "  +mAppManaGridView.getLastVisiblePosition());
        for(int visiblePosition = mAppManaGridView.getFirstVisiblePosition(); visiblePosition <= mAppManaGridView.getLastVisiblePosition(); visiblePosition++) {
            View item = mAppManaGridView.getChildAt(visiblePosition);
            // make something
            Log.d("adan", "adan>" + item.getWidth()+","  +item.getHeight() );

        }

    }

我也尝试过这段代码，但返回项为null，它与nullPointerException一起崩溃

    if(mAppManaGridView.getCount()>0)
    {                                                                       
        mAppManaGridView.setSelection(0);
        Log.d("adan", "adan>" + mAppManaGridView.getCount());
        View item = mAppManaGridView.getChildAt(0);
        // make something
        Log.d("adan", "adan>" + item.getWidth()+","  +item.getHeight() );
    }

你能帮我解决这个问题吗？这让我很困扰。

getChildAt（）返回GridView的子视图。子视图位置和数据位置不一样，因为AdapterViews回收和重用子视图。这样，适配器中可以有100项数据，gridview中只能有7个子视图

这是最基本的，你应该观看关于listview的google IO视频（他们描述的内容主要针对所有AdapterNews）

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如果项目是动态生成的，那么如何获取GridView的项目大小？

    if(mAppManaGridView.getCount()>0)
    {                                                                       
        mAppManaGridView.setSelection(0);
        Log.d("adan", "adan>" + mAppManaGridView.getCount());
        View item = mAppManaGridView.getChildAt(0);
        // make something
        Log.d("adan", "adan>" + item.getWidth()+","  +item.getHeight() );
    }