listview(3、动态刷新）

listview的动态刷新主要是调用adapter的notifyDataSetChanged。

在下面的例子中除了记录正常的刷新外，还记录一种错误的情况（注释掉的），作为备忘。

notifyDataSetChanged除了数据无改变时不起作用，当数据的引用变化时也不起作用。因此在下面那个用数组的例子里，listview不会更新。

package com.example.demo_dlv;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends Activity {

    private ListView lv;
    /*private String[] strs = new String[] {
            "first", "second", "third", "fourth", "fifth"
            };*/
    private List<String> list;
    private static int i = 0;
    private ArrayAdapter<String> adapter;

    private Handler handler = new Handler(){
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case 1:
                /*List<String> list = new ArrayList<String>();
                for (int i=0; i<strs.length; i++) {
                    if(!list.contains(strs[i])) {
                        list.add(strs[i]);
                    }
                }

                list.add("new Element" + i++);*/
                list.add("item" + i++);

                System.out.println(list.size());

                //strs =  (String[]) list.toArray(new String[1]); 引用变了，无法动态刷新

                adapter.notifyDataSetChanged();
                break;
            }
            super.handleMessage(msg);
        }
    };

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

        lv = (ListView) findViewById(R.id.lv); 

        list = new ArrayList<String>();
        list.add("item1");
        list.add("item2");
        list.add("item3");
        list.add("item4");
        list.add("item5");

        adapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, list);
        lv.setAdapter(adapter);

        MyThread mt = new MyThread();
        new Thread(mt).start();
    }

    class MyThread implements Runnable{

        @Override
        public void run() {
            int i = 0;
            while(i < 3){
                try {
                    Thread.sleep(3000);
                    Message message = new Message();
                    message.what = 1;
                    handler.sendMessage(message);
                    i++;
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}