我的适配器上的notifyDataSetChanged() 不更新列表视图，为什么？

发布于 2024-12-12 06:30:22 字数 1270 浏览 0 评论 0原文

我有一个扩展listactivity的活动，在这个类中扩展我有一个扩展baseadapter的类。

现在在我的列表活动中我有这个 onCreate

 /** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {   
    super.onCreate(savedInstanceState);
    setListAdapter(new BuildingAdapter(this));

    final ProgressDialog loading = new ProgressDialog(this);
    loading.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    loading.setTitle("Laddar");
    loading.setMessage("Hämtar data från servern");
    loading.show();

    new AsyncTask<Void, Void, DataPacket.Data>()
    {
        @Override
        protected DataPacket.Data doInBackground(Void... params){
            return ServerConnection.getBuildings();
        }

        @Override
        protected void onPostExecute(DataPacket.Data param) {
            ((MainenanceApplication)getApplication()).setDataStructure(param);
            loading.dismiss();
            //((BuildingAdapter)getListAdapter()).notifyDataSetChanged();
            setListAdapter(new BuildingAdapter(BuildingSelectionActivity.this));
        }

    }.execute();
}

这按预期工作，但我的问题是在 onPostExecute 中我更新了列表适配器使用的数据结构。为什么我不能直接调用notifyDataSetChanged？

如果我有该行，视图不会自行更新，但如果我使用 setListAdapter 下的行，则一切正常。

原文

I have a activity that extends listactivity, extended in this class i have a class that extends baseadapter.

now in my listactivity i have this onCreate

 /** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {   
    super.onCreate(savedInstanceState);
    setListAdapter(new BuildingAdapter(this));

    final ProgressDialog loading = new ProgressDialog(this);
    loading.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    loading.setTitle("Laddar");
    loading.setMessage("Hämtar data från servern");
    loading.show();

    new AsyncTask<Void, Void, DataPacket.Data>()
    {
        @Override
        protected DataPacket.Data doInBackground(Void... params){
            return ServerConnection.getBuildings();
        }

        @Override
        protected void onPostExecute(DataPacket.Data param) {
            ((MainenanceApplication)getApplication()).setDataStructure(param);
            loading.dismiss();
            //((BuildingAdapter)getListAdapter()).notifyDataSetChanged();
            setListAdapter(new BuildingAdapter(BuildingSelectionActivity.this));
        }

    }.execute();
}

This works as it's supposed to, but my question is in onPostExecute I update the datastructure that the list adapter uses.
Why cant I just call notifyDataSetChanged ??

If I have that line the view does not update itself, but if I use the line under where I do setListAdapter, it all works.

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

魔 2024-12-19 06:30:22

如果适配器已经设置，再次设置将不会刷新列表视图。相反，首先检查列表视图是否有适配器，然后调用适当的方法。

我认为在设置列表视图时创建适配器的新实例不是一个好主意。相反，创建一个对象。

BuildingAdapter adapter = new BuildingAdapter(context);

    if(getListView().getAdapter() == null){ //Adapter not set yet.
     setListAdapter(adapter);
    }
    else{ //Already has an adapter
    adapter.notifyDataSetChanged();
    }

If the adapter is already set, setting it again will not refresh the listview. Instead first check if the listview has a adapter and then call the appropriate method.

I think its not a very good idea to create a new instance of the adapter while setting the list view. Instead, create an object.

BuildingAdapter adapter = new BuildingAdapter(context);

    if(getListView().getAdapter() == null){ //Adapter not set yet.
     setListAdapter(adapter);
    }
    else{ //Already has an adapter
    adapter.notifyDataSetChanged();
    }

回复收藏 0 原文