动态刷新listview数据



之前一直困扰listview刷新后位置的问题，现在才明白，原来不能重新设置listview的adapter，而应该用notifyDataSetChanged()来刷新，这样位置就不会置顶。

下面做了一个测试的例子，点击最后一条记录，会增加一条新的记录，

代码如下,使用继承SimpleAdapter

1.TestAdapter

package com.TestAdapter;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.AbsListView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

public class TestAdapter extends Activity {
    /** Called when the activity is first created. */
    private int[] images ;
    private ListView listview;
    private MyAdapter adapter;
    List> al;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        images =  new int[]{android.R.drawable.ic_btn_speak_now,
                android.R.drawable.alert_light_frame,
                android.R.drawable.arrow_down_float,
                android.R.drawable.arrow_up_float,
                android.R.drawable.btn_star_big_off,
                android.R.drawable.btn_star_big_on,
                android.R.drawable.button_onoff_indicator_off,
                android.R.drawable.button_onoff_indicator_on,
                android.R.drawable.checkbox_off_background,
                android.R.drawable.checkbox_on_background,
                android.R.drawable.ic_btn_speak_now,
                android.R.drawable.ic_delete};
        listview = (ListView)findViewById(R.id.listview);
        al = new ArrayList>();
        for(int i=0; i<12; i++){
            HashMap map = new HashMap();
            map.put(""+i, images[i]);
            al.add(map);
        }

        adapter = new MyAdapter(this, al, R.layout.list_item, new String[]{"imageview", "tv"}, 
                new int[]{R.id.imageview, R.id.tv});
        listview.setAdapter(adapter);
        listview.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView arg0, View arg1, int count,
                    long arg3) {
                if(adapter.getCount()==count+1){
                    HashMap map = new HashMap();
                    map.put(""+(adapter.mItemList.size()), android.R.drawable.ic_dialog_email);
                    al.add(map);
                    adapter.mItemList = al;
                    adapter.notifyDataSetChanged();
                    Toast.makeText(TestAdapter.this, "正在刷新", Toast.LENGTH_SHORT).show();
                }                
            }
        });
        
    }
    
    
    private class MyAdapter extends SimpleAdapter{
        int count = 0;
        private List> mItemList;
        public MyAdapter(Context context, List> data,
                int resource, String[] from, int[] to) {
            super(context, data, resource, from, to);
            mItemList = (List>) data;
            if(data == null){
                count = 0;
            }else{
                count = data.size();
            }
        }
        public int getCount() {
            return mItemList.size();
        }

        public Object getItem(int pos) {
            return pos;
        }

        public long getItemId(int pos) {
            return pos;
        }
        
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            Map map = mItemList.get(position);
            int image  =  map.get(""+position);
            View view = super.getView(position, convertView, parent);
            ImageView imageview = (ImageView)view.findViewById(R.id.imageview);
            TextView tv = (TextView)view.findViewById(R.id.tv);
            imageview.setBackgroundResource(image);
            tv.setText(""+position);
            return view;
        }
    }
}

下面我们再来看看使用继承BaseAdapter来刷新listview数据：

public class PersonAdapter extends BaseAdapter {
	private ArrayList mList;
	private Context mContext;
	
	public PersonAdapter(ArrayList list, Context context) {
		mList = list;
		mContext = context;
	}
	
	public void refresh(ArrayList list) {
		mList = list;//传入list，然后调用notifyDataSetChanged方法
		notifyDataSetChanged();
	}
	

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

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

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

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		Holder holder = null;
		if (convertView == null) {
			LayoutInflater inflater = LayoutInflater.from(mContext);
			convertView = inflater.inflate(R.layout.list_item, null);
			holder = new Holder();
			holder.mNameText = (TextView)convertView.findViewById(R.id.name_text);
			holder.mIDText = (TextView)convertView.findViewById(R.id.id_text);
			convertView.setTag(holder);
		} else {
			holder = (Holder) convertView.getTag();
		}
		holder.mNameText.setText(mList.get(getCount() - position - 1).getName());
		holder.mIDText.setText(mList.get(getCount() - position - 1).getID());
		return convertView;
	}

	class Holder {
		private TextView mNameText, mIDText;
	}
}

在使用这种类型时，在Activity使用mAdapter.notifyDataSetChanged()时候，有时候会发现数据不能够及时的更新。下面看一下主Activity：

public class ListViewRefreshActivity extends Activity {

	private ListView mListView;
	private ArrayList mList;
	private PersonAdapter mAdapter;
	private Handler mHandler;
	private String mName, mID;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		mListView = (ListView)findViewById(R.id.listView);
		mList = new ArrayList();
		mAdapter = new PersonAdapter(mList, ListViewRefreshActivity.this);
		mListView.setAdapter(mAdapter);

		mHandler = new Handler() {

			@Override
			public void handleMessage(Message msg) {
				super.handleMessage(msg);
				mList.add((PersonBean) msg.obj);
				Log.v("@@@@@@", "this is get message");
				mAdapter.refresh(mList);
//				mAdapter.notifyDataSetChanged();
			}
		};

//		final Message message = new Message();
		new Thread(new Runnable() {

			@Override
			public void run() {
				try {
					for (int i = 0; i < 10; i++) {
						mName = "hao :" + i;
						mID = "" + i;
						PersonBean bean = new PersonBean();
						bean.setID(mID);
						bean.setName(mName);
						Message message = new Message();
						message.obj = bean;
						Thread.sleep(3000);
						mHandler.sendMessage(message);
//						mHandler.sendMessageDelayed(message, 10000);
					}}catch (Exception e) {
						e.printStackTrace();
					}
			}
		}).start();
	}
}