简化版消息处理

Handler.java

import java.util.Queue;

public class Handler {

    Looper mLooper;
    MessageQueue mQueue;



    //
    public Handler(){
        //
        mLooper = Looper.myLooper();
        mQueue = mLooper.mQueue;
        Log.log("mLooper ＝ "+mLooper);
    }

    public void sendMessage(Message msg){
        msg.target = this;
        mQueue.add(msg);
    }

    public void handMessage(Message message){

    }
}

Looper.java

public class Looper {

   static final ThreadLocal sThreadLocal = new ThreadLocal<>();
   static Looper sMainLooper;

   MessageQueue mQueue ;
   Thread mThread;

   public Looper(){
       mQueue = new MessageQueue();
       mThread = Thread.currentThread();
   }

   public static void prepare(){
       //不能准备两次
       if (sThreadLocal.get() != null) {
           throw new RuntimeException("Only one Looper may be created per thread");
       }
       //为线程绑定一个Looper 这个looper 可在多线程中共享
       Looper looper = new Looper();
       sThreadLocal.set(looper);
   }

   //looper
   public static Looper myLooper(){
       return  sThreadLocal.get();
   }

   public static void looper(){
       Looper looper = Looper.myLooper();
       while (true){

           //无限循环
           MessageQueue queue = looper.mQueue;
           Message message = queue.next();
           if (message!=null){
               message.target.handMessage(message);
           }
       }
   }

   //这个函数只在main当中调用一次
   public static void prepareMainLooper() {
       prepare();
       synchronized (Looper.class) {
           if (sMainLooper!=null){
               throw new IllegalStateException("The main Looper has already been prepared.");
           }
           sMainLooper = myLooper();
       }
   }
}

Message.java

public class Message {

    Message pre;
    Message next;
    Handler target;

    private String messageId;
    private String message;

    public static Message obtain( String messageId , String msg){
        Message message = new Message();
        message.message = msg;
        message.messageId = messageId;
        return message;
    }

    @Override
    public String toString() {

        return "messageId＝"+messageId + "message="+message;
    }
}

MessageQueue.java

public class MessageQueue {


    Message message;

    boolean isBlock = false;

    public MessageQueue(){

    }

    public Message next(){
        while (true){
            synchronized (this){
                if (message != null){
                    isBlock = false;
                    Message msg = this.message;
                    this.message = this.message.next;
                    return msg;
                }
                if (message == null){
                    Log.log("没有消息");
                    isBlock = true;
                }

                try {
                    this.wait(16);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public void add(Message msg){
        synchronized (this){
            if (message == null){
                this.message = msg;
            }else {
                Message p = message;
                while (p.next != null){
                    p = p.next;
                }
                p.next = msg;
            }
        }
    }
}

Log.java

public class Log {

  public static void log(String msg){
      System.out.println(msg);
  }
}

UI.java 测试用的

public class UI {


    public static void main(String[] s){

        Looper.prepareMainLooper();

        Handler handler = new Handler(){
            @Override
            public void handMessage(Message message) {
                super.handMessage(message);
                Log.log("time = "+System.currentTimeMillis() + " Thread " + Thread.currentThread().getName()+ " 我收到消息 message "  + message.toString());
            }
        };


        handler.sendMessage(Message.obtain("1" , "string1"));


        //模拟发消息线程 t1
        Thread t1 = new Thread(new Runnable() {
            int messageId = 0;
            @Override
            public void run() {
                while (true){

                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    Message message = Message.obtain(messageId +"", "来自线程t1");
                    handler.sendMessage(message);

                    messageId++;
                }
            }
        });

        t1.setName("t1");
        t1.start();

        //模拟发消息线程 t2
        Thread t2 = new Thread(new Runnable() {
            int messageId = 0;
            @Override
            public void run() {
                while (true){

                    try {
                        Thread.sleep(300);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    //一次发10条
                    for (int i = 0; i < 10; i++) {
                        Message message = Message.obtain(messageId +" ", "来自线程t2");
                        handler.sendMessage(message);

                        messageId++;
                    }

                }
            }
        });

        t2.setName("t1");
        t2.start();
        Looper.looper();
    }
}