Question

我正在使用BaseAdapter来填充ListView

但是当它更新时它会重置为新项目。我怎样才能保持现状。我搜索过并找到了一些代码，但它对我没用。

这是我的代码：

public  void appendToMessageHistory(ArrayList username, ArrayList message) {
    if (username != null && message != null) {

        if(lv.getAdapter()==null){

            adapter = new ChatListAdapter(this, name, messages);
        lv.setAdapter(adapter);
        adapter.notifyDataSetChanged();}
        else{
            //int i=lv.getFirstVisiblePosition();
        adapter.updateData(this, name, messages);
        adapter.notifyDataSetChanged();

        //lv.smoothScrollToPosition(i);
        }

    }
}

和我的BaseAdapter：

  public class ChatListAdapter extends BaseAdapter {
  private Context context;
private ArrayList<String> names;
private ArrayList<String> messages;


static class ViewHolder {
     public TextView name, message;
     public ImageView image;
}

public ChatListAdapter(Context context, ArrayList<String> names, ArrayList<String>   messages) {

     this.context = context;
    this.names = names;
     this.messages = messages;

}
public void updateData(Context context, ArrayList<String> names, ArrayList<String> messages){
    this.context = context;
    this.names = names;
    this.messages = messages;


}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View rowView = convertView;
    if (rowView == null) {
        LayoutInflater inflater = LayoutInflater.from(context);

            rowView = inflater.inflate(R.layout.layout,
                null);

        ViewHolder viewHolder = new ViewHolder();
        viewHolder.name = (TextView) rowView.findViewById(R.id.name);
        viewHolder.message=(TextView) rowView.findViewById(R.id.firstLine);
        rowView.setTag(viewHolder);
    }

    ViewHolder holder = (ViewHolder) rowView.getTag();
    String name = names.get(position);
    String message = messages.get(position);

           holder.message.setTextColor(context.getResources().getColor(this.getTextColorID()));



    return rowView;
}

@Override
public int getCount() {
    return names.size();
}

@Override
public Object getItem(int position) {
    return names.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}
@Override
public int getViewTypeCount() {
    // you have two different row types
    return 2;
}

@Override
public int getItemViewType(int position) {
    // You need to tell to adapter which row is needed at given position
    return names.get(position).equals(own) ? 0 : 1;
}

  }

我也在使用stackFromBottom = true

我已经使用了smoothScrollToPosition（），但是在重置listview之后它会回滚到位置，即使适配器更新，我也希望坚持当前位置。

Answer 1

您是否尝试过setSelectionFromTop方法？

在appendToMessageHistory方法的else块中，尝试：

int index = lv.getFirstVisiblePosition();
View v = lv.getChildAt(0);
int top = (v == null) ? 0 : v.getTop();

adapter.updateData(this, name, messages);
adapter.notifyDataSetChanged();

lv.setSelectionFromTop(index, top);

可在此处找到对此的解释：Maintain/Save/Restore scroll position when returning to a ListView

Answer 2

我解决了我的错误。

非常简单

它将notifyDataSetChanged()函数绑定到特定条件

这是我的代码：

 public  void appendToMessageHistory(ArrayList username, ArrayList message) {
    if (username != null && message != null) {

        if(lv.getAdapter()==null){

            adapter = new ChatListAdapter(this, name, messages);
        lv.setAdapter(adapter);
        adapter.notifyDataSetChanged();
  }
        else{
            int i = lv.getFirstVisiblePosition();
            int last = lv.getLastVisiblePosition();
            View v = lv.getChildAt(0);
            int top = (v == null) ? 0 : v.getTop();
            if (top < 0 && lv.getChildAt(1) != null) {
                    i++;
                    v = lv.getChildAt(1);
                    top = v.getTop();
            }



            adapter.updateData(this, name, messages);
            if(last==messages.size()-2)
                adapter.notifyDataSetChanged();
            lv.setSelection(i);
            lv.setSelectionFromTop(i, top);


        }

    }
}

如果它没有显示最后一个项目并且它是否显示最后一个项目，那么它不会保留在当前位置，那么它将通知。

ListView在更新后重置

2 个答案: