android - 实例化和设置新的自定义适配器有效，但 notifyOnDataSetChanged() 无效

Question

我在使用 notifyOnDataSetChanged() 时遇到问题。 我可以通过创建新的 CustomAdapter 来让我的 ListView 加载新数据，但不能使用 notifyOnDataSetChanged()。

private void repopulateListView(JSONObject resp) throws JSONException {
    arrayList.clear();
    List<MyObject> newArrayList = getData(); 
    arrayList.addAll(newArrayList); //I've checked that arrayList contains new data

    /* WORKS, new data is loaded in the list view */
    adapter = new CustomAdapter(MainActivity.this, arrayList);
    listView.setAdapter(adapter);
}

而以下内容不起作用 - ListView 未刷新，它只是保持检索新数据之前的状态。我已检查新数据是否已正确检索。

private void repopulateListVIew(JSONObject resp) throws JSONException {
    arrayList.clear();
    List<MyObject> newArrayList = getData(); 
    arrayList.addAll(newArrayList); //I've checked that arrayList contains new data

    /* DOES NOT WORK, list view does not refresh with new data */
    ((BaseAdapter)adapter).notifyOnDataSetChanged();
}

我的适配器是这样定义的:

adapter = new CustomAdapter(MainActivity.this, arrayList);
listView = (ListView) findViewById(R.id.list_view); 
listView.setAdapter(adapter);
listView.setOnItemClickListener(
            new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    //additional code
                    startActivity(DetailsActivity);
                }
            }
    );

更新:@Sabeeh 的回答有效。根据下面@Sabeeh 和@ViniciusRodriguesLima 的回答，我不得不按如下方式编辑我的 CustomAdapter.java 以引用 list 变量(除了添加 update() 方法):

public class CustomAdapter extends ArrayAdapter<MyObject> {
    private Context context;
    private List<MyObject> list = new ArrayList<>(); //add this variable

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater inf = LayoutInflater.from(getContext());
        View customView = inf.inflate(R.layout.custom_beer_row, parent, false);
        //final MyObject chosenObj = getItem(position); Changed to the statement below
        final MyObject chosenObj = list.get(position); //this is CORRECT
        ...
    }

我尝试了以下页面中的建议但无济于事:

• notifyDataSetChange not working from custom adapter
• notifyDataSetChanged not working
• Android: notifyDataSetChanged(); not working
  • 按照最高投票答案的说明，使用 adapter.clear() 似乎也清除了我的 arrayList，所以当我使用 notifyOnDataSetChanged() 时, arrayList 为空)

如有任何帮助，我们将不胜感激。

Answer 1

请试试这个:

private void repopulateListVIew(JSONObject resp) throws JSONException {
    arrayList.clear();
    List<MyObject> newArrayList = getData();
    arrayList.addAll(newArrayList);
    adapter.update(arrayList);
}

并在您的 CustomAdapter 类中编写以下函数

public void update(ArrayList<MyObject> list) {
    //replace arrayList variable with your class ArrayList variable
    this.arrayList = list;
    this.notifyDataSetChanged();
}

当您将数据源对象传递给适配器时，您只是按值传递它。当您在 Activity 范围内刷新数据时，您的适配器对此一无所知。这就是为什么 Sabeeh 在适配器内部创建了一个更新方法，这样他就可以更新其适配器数据源。 – Vinicius Rodrigues Lima

希望对你有帮助