listview getChildAt()返回null [英] listview getChildAt() Return null

问题描述

我一直在从事android项目，并遇到了问题.我用谷歌搜索，但没有找到答案.在我的项目中，有一个名为 viewsurahfragment 的片段，它包含一个ID为 lv_showquran 的listview.

I have been working on an android project and stuck in a problem. I googled it but found no answer. In my project, there is a fragment named viewsurahfragment and it contains a listview whose id is lv_showquran.

我想突出显示指定索引处的listview的视图.我正在使用listview.getchildat()，但它返回 null 值.
这是viewsurahfragment的代码.发出不相关的功能.

I want to highlight the view of the listview at specified index. I am using listview.getchildat() but it return null value.
Here is the code for viewsurahfragment. Irrelevant functions are emited.

public class ViewSurahFragment extends Fragment
{
    private ListView listView;
    private int currentSurah;
    private String surahName;
    private DatabaseHelper databaseHelper;
    private ArrayAdapter<String> arrayAdapter;

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState)
    {
        super.onViewCreated(view, savedInstanceState);
        //        this.listView = (ListView) getActivity().findViewById(R.id.lv_showQuran);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState)
    {
        super.onActivityCreated(savedInstanceState);
        this.listView = (ListView) getActivity().findViewById(R.id.lv_showQuran);
    }

    private void displayAyas()
    {
        String[] values = this.getSurahAyas();
        this.listView.setItemsCanFocus(true);
        this.arrayAdapter = new ArrayAdapter<>(this.getActivity().getApplicationContext(), R.layout.layout_surah_ayah, values);

        this.listView.setAdapter(this.arrayAdapter);
        this.listView.setOnItemClickListener(new AdapterView.OnItemClickListener()
        {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id)
            {
            }
        });

        registerForContextMenu(this.listView);
    }

    public void highlightAyah(int ayahNum)
    {
        TextView view = (TextView) this.listView.getChildAt(ayahNum - 1);
        Log.i("ViewSurahFragment", "List View Child Counts Are: " + this.listView.getChildCount());

        if(view == null)
            Log.i("ViewSurahFragment", "view is null");
    }
}

无论是在 onactivitycreated 中还是在 onviewcreated 中使用了以下代码行，它在调用 highlightayah中的listview.getchildat()时都返回null.函数.

Don't metter whether i used following line of code either in onactivitycreated or in onviewcreated, it returned null on calling listview.getchildat() in highlightayah function.

this.listView = (ListView) getActivity().findViewById(R.id.lv_showQuran);

我也尝试执行以下操作，但它对我也无效.

I also tried to do following, but it also didn't work for me.

ListView view = (ListView) getActivity().findViewById(R.id.lv_showQuran);
TextView v = (TextView) view.getChildAt(ayahNum);
Log.i("ViewSurahFragment", "List View Child Counts Are: " + view.getChildCount());

if(v == null)
    Log.i("ViewSurahFragment", "view is null");

但是对我来说有趣的是，在我使用的两种解决方案中， getchildviewcount()返回0 ，但项目显示在列表视图中.
有人可以告诉我我在哪里做错事.
预先感谢您的帮助.

But the interesting thing for me is that getchildviewcount() return 0 in either solutions i used, but items are displayed in the listview.
Can anybody please tell me where i'm doing mistake.
Thanks in advance for helping.

推荐答案

这将产生null:

 TextView textView = (TextView) listView.getChildAt(0);
 Log.i("item", textView.getText().toString());

这不是:

    TextView textView = (TextView) listView.getAdapter().getView(0, null, listView);
    Log.i("item", textView.getText().toString());

此示例使用了 android.R.layout.simple_list_item_1 ，因此请记住，TextView是simple_list_item_1中的根视图.

This example used android.R.layout.simple_list_item_1 so keep in mind that TextView is root view in simple_list_item_1.

这篇关于listview getChildAt()返回null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！