消息類(Message)：

package p;

public class Message {

private Runnable runnable;

private long start;

private long delay;

public Message(Runnable runnable, long delay) {

start = System.currentTimeMillis();

this.runnable = runnable;

this.delay = delay;

}

public void handle() {

runnable.run();

}

public boolean canHandle() {

return delay <= System.currentTimeMillis() - start;

}

}消息隊列(MessageQueue)：

package p;

import java.util.ArrayList;

import java.util.List;

public class MessageQueue {

private List messages = new ArrayList();

private int cursor = -1;

/**

* 入隊

*

* @param message

*/

public void push(Message message) {

messages.add(message);

}

/**

* 移出隊列

*

* @param message

*/

public void remove(Message message) {

messages.remove(message);

cursor--;

}

/**

* 出隊

*

* @return

*/

public Message pop() {

Message message = null;

if (!messages.isEmpty()) {

message = messages.get(++cursor);

if (cursor == messages.size() - 1) {

cursor = -1;

}

}

return message;

}

}

每個線程擁有一個消息隊列。

消息管理類(MessageManager)：

package p;

public class MessageManager {

private static ThreadLocal local = new ThreadLocal();

/**

* 消息入隊

* @param message

*/

public static void addMessage(Message message) {

local.get().push(message);

}

/**

* 創建消息隊列

*/

public static void prepare() {

MessageQueue queue = local.get();

if (queue != null) {

throw new RuntimeException("每個線程只能有一個消息隊列！");

}

local.set(new MessageQueue());

}

/**

* 開啟消息循環

*/

public static void loop() {

MessageQueue messageQueue = local.get();

Message message;

while ((message = messageQueue.pop()) != null) {

if (message.canHandle()) {

messageQueue.remove(message);

message.handle();

}

}

}

}

模擬handler類(Handler)：

package p;

public class Handler {

public void post(Runnable runnable, long delay) {

Message message = new Message(runnable, delay);

MessageManager.addMessage(message);

}

}

模擬activity的類(MainUI)：

package p;

public class MainUI {

public void onCreate() {

System.out.println("onCreate:" + Thread.currentThread().getName());

new Handler().post(new Runnable() {

@Override

public void run() {

System.out.println("post after 3 minutes:"

+ Thread.currentThread().getName());

}

}, 3000);

new Handler().post(new Runnable() {

@Override

public void run() {

System.out.println("post after 6 minutes:"

+ Thread.currentThread().getName());

}

}, 6000);

new Thread(new Runnable() {

@Override

public void run() {

MessageManager.prepare();

new Handler().post(new Runnable() {

@Override

public void run() {

System.out.println("post after 9 minutes:"

+ Thread.currentThread().getName());

}

}, 9000);

new Handler().post(new Runnable() {

@Override

public void run() {

System.out.println("post after 12 minutes:"

+ Thread.currentThread().getName());

}

}, 12000);

MessageManager.loop();

}

}).start();

System.out.println("End onCreate!");

}

}模擬android啟動activity的類(Main)：

package p;

public class Main {

public static void main(String[] args) {

Runnable runnable = new Runnable() {

@Override

public void run() {

MessageManager.prepare();

MainUI mainUI = new MainUI();

mainUI.onCreate();

MessageManager.loop();

}

};

Thread main = new Thread(runnable);

main.setName("main");

main.start();

}

}執行輸出：

onCreate:main

End onCreate!

post after 3 minutes:main

post after 6 minutes:main

post after 9 minutes:Thread-1

post after 12 minutes:Thread-1

總結

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