一、work线程向main线程发送数据（work线程发数据，main线程处理数据）

public class MainActivity extends Activity {       private Button button;    private TextView textView;    private Handler handler;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        button = (Button)this.findViewById(R.id.button1);        textView = (TextView)this.findViewById(R.id.textView1);         handler = new MyHandler();        button.setOnClickListener(new OnClickListener() {                        @Override            public void onClick(View arg0) {
                      new Thread(){                    @Override                    public void run() {                        super.run();                        Thread.currentThread().getName();//获取当前线程的名字                        Message msg = Message.obtain();                        String s = "hello handler";                        msg.obj = s;                        handler.sendMessage(msg);                    }                                             }.start();                }        });    }         public class MyHandler extends Handler{        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            String s = (String)msg.obj;            textView.setText(s);                    }        }}

　二、main线程向work线程发送数据（main线程发数据，work线程处理数据）

 

public class MainActivity extends Activity {    private Button button;    private TextView textView;    private Handler handler;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        button = (Button)this.findViewById(R.id.button);        textView = (TextView)this.findViewById(R.id.textview);                button.setOnClickListener(new OnClickListener() {                        @Override            public void onClick(View v) {                Message msg = Message.obtain();                msg.obj = "handler2";                handler.sendMessage(msg);            }        });        new Thread(){            @Override            public void run() {                super.run();                Looper.prepare();//第一步                handler = new Handler(){
    //第二步                    @Override                    public void handleMessage(Message msg) {                        super.handleMessage(msg);                        String s = (String) msg.obj;                        System.out.println(s);                            }                                                        };                Looper.loop();//第三步            }        }.start();                }}

 

三、Handler、Looper、MessageQueue的工作原理　

 

 

 

handler可以在任意线程发送消息

 

一个线程可以有多个Handler，但是只能有一个Looper！