Question

我想将新项目附加到ListView以启用无限滚动。

private ListAdapter adapter;
ArrayList < HashMap < String, String >> listViewList;

...

class GetItems extends AsyncTask < String, String, String > {

    protected String doInBackground(String...args) {
        ...

        for (int i = 0; i < items.length(); i++) {
            ...
            HashMap < String, String > map = new HashMap < String, String > ();
            map.put("name_1", name_1);
            map.put("name_2", name_3);
            map.put("name_3", name_3);

            listViewList.add(map);
        }
    }

    protected void onPostExecute(String file_url) {
        adapter = new CustomAdapter(Activity.this, listViewList,
            R.layout.single_item, new String[] {}, new int[] {});
        setListAdapter(adapter);
    }
}

GetItems课程会根据您提供的页码获取新项目。我想将新项目附加到onPostExecute上的现有ListView项目。

知道该怎么做吗？

Answer 1

实际上，您只需在adapter.notifyDataSetChanged中拨打onPostExecute即可。但是你不应该多次实例化适配器。它应该只做一个，所以整体看起来像这样

private ListAdapter adapter;

...
void onCreate(){ // assuming this is an activity
   adapter = new CustomAdapter(Activity.this, listViewList,
             R.layout.single_item, new String[] {}, new int[] {});
   setListAdapter(adapter);
}

class GetItems extends AsyncTask<String, String, String> {
  ...  

   protected void onPostExecute(String file_url) {
     adapter.notifyDataSetChanged();
   }
}

Answer 2

在GitHub上查看这个库

https://github.com/codepath/android_guides/wiki/Endless-Scrolling-with-AdapterViews

根据您的评论编辑：

你需要忘记ListActivity并且你曾经听说它存在，它对你想要做的事情毫无用处。

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;



public class DemosAdapter extends BaseAdapter {

    public List<DemoItem> listOfItems;
    private View v;
    private ViewWrapper wrapper;
    private Context context;

    public DemosAdapter(Context c, List<DemoItem> listOfItems) {
        this.context = c;
        this.listOfItems = listOfItems;
    }

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

    @Override
    public DemoItem getItem(int i) {
        return listOfItems.get(i);
    }

    @Override
    public long getItemId(int i) {
        return 0;
    }

    public void sort() {
        Collections.sort(listOfItems, new Comparator<DemoItem>() {
            @Override
            public int compare(DemoItem item, DemoItem item2) {
                return item.getName().compareTo(item2.getName());
            }
        });
    }

    public void addItems(List<DemoItem> listOfFreshItems){
        listOfItems.addAll(listOfFreshItems);
        notifyDataSetChanged();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        DemoItem itm = listOfItems.get(position);

        v = convertView;

        if (v == null) {
            LayoutInflater inflater = LayoutInflater.from(context);
            v = inflater.inflate(R.layout.demo_item, null, false);
            wrapper = new ViewWrapper(v);
            v.setTag(wrapper);
        }
        else {
            wrapper = (ViewWrapper) v.getTag();
        }

        wrapper.getTvDemoName().setText(itm.getName());

        return v;
    }

    private class ViewWrapper {

        private View base;
        private TextView tvDemoName;

        public ViewWrapper(View v) {
            this.base = v;
        }

        public TextView getTvDemoName() {
            if (tvDemoName == null) {
                tvDemoName = (TextView) base.findViewById(R.id.tvDemoName);
            }
            return tvDemoName;
        }

    }
}

首次添加数据时，请执行此操作

demosAdapter = new DemosAdapter(this, listOfDemos);
demosAdapter.sort();
lvListOfDemos.setAdapter(demosAdapter);

获得新商品时，请致电

adapter.addItems(List<DemoItem> newItems);

将项目附加到ListView

2 个答案: