java - listview.setAdapter(null) 似乎不起作用

Question

我有一个选项卡布局包含一个 ListView ，每次选择选项卡时该 View 都会更新 但新项目将添加到列表中，并且在添加新项目之前列表不会被清除

public class DemoObjectFragment extends Fragment {
ListView lv;
private String TAG = DemoObjectFragment.class.getSimpleName();
public static ArrayList<HashMap<String, String>> contList = new ArrayList<>();
android.widget.ListAdapter adapter;

@Override
public View onCreateView(LayoutInflater inflater,
                         ViewGroup container, Bundle savedInstanceState) {
    View vw = inflater.inflate(R.layout.coin, container, false);
    try {
        for (int i = 0; i < contactList.size(); i++) {
            Log.v(TAG, "Response: " + contactList.get(i));
            if (Integer.valueOf(contactList.get(i).get("asset_id")) == MainActivity.typeCurrency) {
                contList.add(contactList.get(i));
            }
        }
    }catch (Exception e){
        e.getMessage();
    }


    lv=vw.findViewById(R.id.exchangeList);
    lv.setAdapter(null);
    adapter = new SimpleAdapter(getActivity(), contList, R.layout.list_item, new String[]{"sourceName", "priceCurrency"},
            new int[]{R.id.sourceName, R.id.priceCurrency});
    lv.setAdapter(adapter);
    contactList=new ArrayList<>();
    return vw;
}

}

Answer 1

您需要在将新项目添加到列表之前清除项目，

 contList.clear();

尝试添加clear()方法。

 try {
    contList.clear();
    for (int i = 0; i < contactList.size(); i++) {
        Log.v(TAG, "Response: " + contactList.get(i));
        if (Integer.valueOf(contactList.get(i).get("asset_id")) == MainActivity.typeCurrency) {
            contList.add(contactList.get(i));
        }
    }
}catch (Exception e){
    e.getMessage();
}