Android，它没有从 ListView 中删除项目

Question

我在一个单独的文件中创建了一个 class 适配器，但在我的主文件中，我正在调用 remove 方法来删除一个项目或任何我 select 的项目，但是当我删除它时，它不会在我的应用程序上更新。

代码：

public static void populateChatListView(final Context context){
    adapter = new myAdapter(context, R.layout.source_contact);

    listv.setAdapter(adapter);

    for (Contacts friend: friends){
        adapter.add(friend);
    }

    listv.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
        @Override
        public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
            Toast.makeText(context, "DELETED", Toast.LENGTH_SHORT).show();
            //supposed to remove it
            adapter.remove(adapter.getItem(0));
           //supposed to update it(notify)
            adapter.notifyDataSetChanged();
            return true;
        }

    });

    adapter.registerDataSetObserver(new DataSetObserver() {
        @Override
        public void onChanged() {
            super.onChanged();
            listv.setSelection(adapter.getCount() - 1);
        }
    });
}

它没有给我任何错误，也没有删除它。如果有任何帮助，我将不胜感激。

CLASS 适配器：

public class myAdapter extends ArrayAdapter<Contacts>{
    private List<Contacts> Listc = new ArrayList<>();
    TextView NameWindow, LastN;
    ImageView contactProfile;

    Context context;

    public myAdapter(Context context, int resource) {
        super(context, resource);
        this.context = context;
    }
    @Override
    public void add(Contacts object) {


        Listc.add(object);
        super.add(object);
    }

    @Override
public Contacts getItem(int position) {
    return Listc.get(position);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    if(convertView == null){
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.source_contact, parent, false);
    }

    NameWindow = (TextView) convertView.findViewById(R.id.contactN);
    LastN = (TextView) convertView.findViewById(R.id.contactL);

    contactProfile = (ImageView) convertView.findViewById(R.id.contactProfile);

    String name, lastn;

    Contacts provider = getItem(position);

    name = provider.getName(); // name goes down
    lastn = provider.getLastn(); // goes upper

    NameWindow.setText(name);
    LastN.setText(lastMessage);

    return convertView;
}
    ...

已编辑。

Answer 1

我认为在你的适配器中你应该有一个像这样的数组变量。

class yourAdapter extends BaseAdapter  {
    private ArrayList<Object> your_list_variable; 
    ....
}

您只需更新此列表，然后调用

adapter.notifyDataSetChanged();

试试吧。

// 在这里更新一个例子，你可以检查我的代码。

public class MainActivity extends ActionBarActivity {

private ListView myList;
private myAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    mAdapter = new myAdapter(this, android.R.layout.simple_list_item_1);
    myList = (ListView) findViewById(R.id.myList);

    for(int i = 0; i < 100; i++) {
        mAdapter.add("item : " + (i+1));
    }
    myList.setAdapter(mAdapter);

    myList.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
        @Override
        public boolean onItemLongClick(AdapterView<?> parent, View view, int index, long id) {

            System.out.println("index : " + index);
            System.out.println("item : " + mAdapter.getItem(index));
            mAdapter.remove(mAdapter.getItem(index));
            mAdapter.notifyDataSetChanged();
            return false;
        }
    });

}


class myAdapter extends ArrayAdapter<String> {

    private List<String> listData = new ArrayList<>();


    public myAdapter(Context context, int resource) {
        super(context, resource);
    }

    @Override
    public void add(String object) {
        super.add(object);

        listData.add(object);
    }

    @Override
    public void remove(String object) {
        super.remove(object);
        listData.remove(object);
    }

    @Override
    public String getItem(int position) {
        return super.getItem(position);
    }
}

希望对您有所帮助。

Answer 2

将此添加到您的适配器中class

public void myRemove(int position){
  Listc.remove(position);
  myAdapter.super.notifyDataSetChanged();
}

并使用它来查看它是否会有所作为

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