Looper和Handler

一般情况下，我们启动一个线程，是让它完成一件任务，完成该任务后，线程就退出了。还有一种情况，我们希望该线程一直在运行，我们会时不时的向该线程发送一些消息，线程接收到该消息后，执行相应的操作，执行完成后，线程不退出，等待下一个消息，这很像所谓的“事件触发”。在Android上，使用Looper和Handler很容易实现该功能。
故名思意，Looper就是一个消息循环，而Handler就是一个消息处理器，在非UI线程中，线程默认是不存在消息循环的，因此在创建Handler的时候会抛出异常，在创建Handler对象之前，必须调用Looper.prepare()，然后创建Handler对象，最后启动消息循环：Looper.loop();

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public class LoopThread extends Thread {
public interface HandlerCreater {
Handler createHandler();
}
private Handler mHandler = null;
private HandlerCreater mHandlerCreater;
LoopThread(HandlerCreater hc) {
mHandlerCreater = hc;
}
@Overwrite
public void run() {
Looper.prepare();
mHandler = mHandlerCreater.createHandler();
Looper.loop();
mHandler = null;
}
public void sendMessage(Message msg) {
if (null != mHandler) {
mHandler.sendMessage(msg);
}
}
}

public class LoopThread extends Thread {
      public interface HandlerCreater {
              Handler createHandler();
      }
      private Handler mHandler = null;
      private HandlerCreater mHandlerCreater;
      LoopThread(HandlerCreater hc) {
            mHandlerCreater = hc;
      }

      @Overwrite
      public void run() {
            Looper.prepare();
            mHandler = mHandlerCreater.createHandler();
            Looper.loop();
            mHandler = null;
      }

      public void sendMessage(Message msg) {
            if (null != mHandler) {
                   mHandler.sendMessage(msg);
            }
      }
}

这样，在主线程中只要实现一个HandleCreater，创建出自己合适的Handler，然后就可以启动线程，并向其发消息了。
跳出消息循环使用：Looper.myLooper().quit();

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print ?

public class LoopThread extends Thread {
public interface HandlerCreater {
Handler createHandler();
}
private Handler mHandler = null;
private HandlerCreater mHandlerCreater;
LoopThread(HandlerCreater hc) {
mHandlerCreater = hc;
}
@Overwrite
public void run() {
Looper.prepare();
mHandler = mHandlerCreater.createHandler();
Looper.loop();
mHandler = null;
}
public void sendMessage(Message msg) {
if (null != mHandler) {
mHandler.sendMessage(msg);
}
}
}

public class LoopThread extends Thread {
      public interface HandlerCreater {
              Handler createHandler();
      }
      private Handler mHandler = null;
      private HandlerCreater mHandlerCreater;
      LoopThread(HandlerCreater hc) {
            mHandlerCreater = hc;
      }

      @Overwrite
      public void run() {
            Looper.prepare();
            mHandler = mHandlerCreater.createHandler();
            Looper.loop();
            mHandler = null;
      }

      public void sendMessage(Message msg) {
            if (null != mHandler) {
                   mHandler.sendMessage(msg);
            }
      }
}

这样，在主线程中只要实现一个HandleCreater，创建出自己合适的Handler，然后就可以启动线程，并向其发消息了。
跳出消息循环使用：Looper.myLooper().quit();

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