Android Handler线程之间通讯

package com.sdyb.kiss.thetest;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

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

public class MainActivity extends AppCompatActivity {

    private Handler handler;
    private Thread t;
    List list = null;
    private TextView txt;

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

        handler = new Firsthadler();

        Button btn = (Button) findViewById(R.id.button);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                t = new Mytheard();
                t.start();
            }
        });

        txt = (TextView) findViewById(R.id.txt1);
    }


    class Firsthadler extends Handler {

        @Override
        public void handleMessage(Message msg) {
            list = (List) msg.obj;
            for (int i = 0; i < list.size(); i++) {
                String ss = list.get(i).toString();
                txt.setText(ss);
            }


        }
    }


    class Mytheard extends Thread {
        @Override
        public void run() {
            Message msg = handler.obtainMessage();
            list = new ArrayList();
            list.add("当前时间:" + new Date().toString());
            list.add("当前时间:" + new Date().toString());
            list.add("当前时间:" + new Date().toString());
            list.add("当前时间:" + new Date().toString());
            msg.obj = list;
            handler.sendMessage(msg);
        }
    }

}