Question

当我从listview活动中打开一个新活动然后返回listview活动或者如果我重新打开相同的listview活动时，我的listview项目会重复出现。

public class PlaylistAdapter extends ArrayAdapter<PlaylistBean> {

    Context context;
    private LayoutInflater inflater;

    public static class ViewHolder
    {
        public final TextView name;
        public final ImageView image;

        public ViewHolder(View view)
        {
            name = (TextView) view.findViewById(R.id.namePlaylist);
            image = (ImageView) view.findViewById(R.id.imagePlaylist);
        }
    }

    public PlaylistAdapter(Context context, List<PlaylistBean> items)
    {
        super(context, R.layout.row_layout_playlist, items);
        inflater = LayoutInflater.from(context);
    }

    @Override
    public View getView(final int position, View convertView, final ViewGroup parent)
    {
        View view = convertView;
        if (view == null)
        {
            LayoutInflater vi = LayoutInflater.from(getContext());
            view = vi.inflate(R.layout.row_layout_playlist, null);
        }

       final ViewHolder viewHolder = new ViewHolder(view);
        PlaylistBean playlistBean = getItem(position);

        viewHolder.name.setText(playlistBean.getName());
        viewHolder.image.setImageResource(playlistBean.getImage());

        return view;
    }

}

这是我的PlaylistBean类

的代码

public class PlaylistBean implements Serializable {

    private int image;
    private String name;

    public PlaylistBean(int image, String name)
    {
        this.image = image;
        this.name = name;
    }

    public int getImage() {
        return image;
    }

    public void setImage(int image) {
        this.image = image;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

以下是我的主要活动的代码

公共类播放列表扩展了AppCompatActivity {

public static List<PlaylistBean> items = new ArrayList<>();
ArrayAdapter<PlaylistBean> myArrayAdapter;

 @Override
     protected void onCreate(Bundle savedInstanceState) 
{
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_playlist);

        playlistListView = (ListView) findViewById(R.id.playlistListView);
        myArrayAdapter = new PlaylistAdapter(Playlist.this, items);
         playlistListView.setAdapter(myArrayAdapter);

            createData();

}

 public void createData()
    {
        PlaylistBean bean1 = new PlaylistBean(R.drawable.popular_upload, "Popular Uploads");
    items.add(bean1);
}

}

Answer 1

当您的活动转到后台时，您可以使用以下代码清除列表视图：

@Override
public void onPause() {
    super.onPause();  // Always call the superclass method first
    yourListView.setListAdapter(null); //This clears the listview items
}

Answer 2

这就是发生的事情。

List<PlaylistBean> items是静态的。
您使用该列表创建ListView
在第一次运行时，ListView变为空，因为items.size()为0
设置适配器后createData()方法调用哪个填充列表。
这会继续填写清单。

如何过来这个。我希望你想在第一次运行时在列表视图中显示一些内容，并希望保留items列表static

@Override
protected void onCreate(Bundle sis){
    super.onCreate(sis);
    setContentView(R.layout.activity_playlist);

    playlistListView = (ListView) findViewById(R.id.playlistListView);
    //fill the list here.
    createData();
    myArrayAdapter = new PlaylistAdapter(Playlist.this, items);
    playlistListView.setAdapter(myArrayAdapter);
}

然后更改您的createData()方法。

public static void createData(){
     //instatiate the list items here
     items=new ArrayList<>();
     PlaylistBean bean1 = new PlaylistBean(R.drawable.popular_upload, "Popular Uploads");
     items.add(bean1);
}

在返回或重新打开活动时，ListView项目会重复出现

2 个答案: