14.Android-使用sendMessage線程之間通訊

https://www.cnblogs.com/lifexy/archive/2020/02/13/12304228.html

1.Handler介紹

Handler 是一個消息分發對象。handler是Android給咱們提供用來更新UI的一套機制，也是一套消息處理機制，經過它能夠實如今不一樣線程之間傳遞消息

本章Handler類要用到的方法有:

void handleMessage(Message msg);    //須要重寫的方法,用來處理接收的消息,只有當接收到發送者發來的消息,纔會回調該方法 Message obtainMessage(); //獲取一個消息對象
boolean sendMessage(Message msg); //發送消息對象,發送成功的話,就會回調handleMessage()方法

 

2.MainActivity.java以下所示:

package com.example.tcpdemo; import java.io.IOException; import java.net.Socket; import java.net.UnknownHostException; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.app.Activity; import android.view.Menu; public class MainActivity extends Activity { MyThread mt; //定義一個handler
    public Handler mHandler = new Handler() { public void handleMessage(Message msg) { //打印發送者發來的消息
            System.out.println("main what:"+msg.what); System.out.println("main obj:"+msg.obj.toString()); System.out.println("main arg1:"+msg.arg1); }; }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mt = new MyThread(); mt.setHandler(mHandler); //設置handler
 mt.start();  //啓動線程 } }

3.MyThread.java以下所示:

package com.example.tcpdemo; import android.os.Handler; import android.os.Message; public class MyThread extends Thread { public Handler mHandler=null; //獲取另外一個線程的Handler
        public void setHandler( Handler handler){ mHandler = handler; } public void run(){ try { //讓線程睡眠3s。
                    Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } Message msg = mHandler.obtainMessage(); //設置發送的內容
             msg.arg1 = 1; msg.what = 3; msg.obj = "this is MyThread"; mHandler.sendMessage(msg); } }

運行打印: