/**
   * Causes the Runnable r to be added to the message queue.
   * 这里源码注释的意思是：把r这个任务对象添加到消息队列中。
   */
  public final boolean post(Runnable r)
  {
    return sendMessageDelayed(getPostMessage(r),0);
  }
/**
   * Enqueue a message into the message queue after all pending messages
*然后我们接着看post方法中直接调用到的发送延时消息的方法，源码注释*的意思是把这个消息放入消息队列，
   */
  public final boolean sendMessageDelayed(Message msg,long delayMillis)
  {
    if (delayMillis < 0) {
      delayMillis = 0;
    }
    return sendMessageAtTime(msg,SystemClock.uptimeMillis() + delayMillis);
  }
/*最后我们再看post中调用的另外一个方法，源码中没有注释，但我们很容易看出来，这个方法就是把r这个任务包装成了一个空的消息并且返回*/
private static Message getPostMessage(Runnable r) {
    Message m = Message.obtain();
    m.callback = r;
    return m;
}

private TextView tv_up;
  private String new_str = "";
  /*post方法解决UI更新问题handler创建方式*/
  private Handler handler_post = new Handler();
  /*sendMessage方法解决UI更新问题handler创建方式*/
  Handler handler_senM = new Handler() {
    public void handleMessage(Message msg) {
      if (msg.what == 1) {
        /*sendMessage方法更新UI的操作必须在handler的handleMessage回调中完成*/
        tv_up.setText(new_str);
      }
    };
  };
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    new Thread(new Runnable() {
      @Override
      public void run() {
        new_str = "更新UI";
        /*sendMessage方法解决UI更新发送消息给handler（主线程中的handler）*/
        handler_senM.sendEmptyMessage(1);
        /*post方法解决UI更新，直接在runnable里面完成更新操作，这个任务会被添加到handler所在线程的消息队列中，即主线程的消息队列中*/
        handler_post.post(new Runnable() {
          @Override
          public void run() {
            tv_up.setText(new_str);
          }
        });
      }
    }).start();
  }

public class HandlerThread extends Thread {
    int mPriority;
    int mTid = -1;
    Looper mLooper;
    private @Nullable Handler mHandler;

    public HandlerThread(String name) {
        super(name);
        mPriority = Process.THREAD_PRIORITY_DEFAULT;
    }

    public HandlerThread(String name, int priority) {
        super(name);
        mPriority = priority;
    }

    protected void onLooperPrepared() {
    }

    @Override
    public void run() {
        mTid = Process.myTid();
        Looper.prepare();
        synchronized (this) {
            mLooper = Looper.myLooper();
            notifyAll();
        }
        Process.setThreadPriority(mPriority);
        onLooperPrepared();
        Looper.loop();
        mTid = -1;
    }

    public Looper getLooper() {
        //Thread.IsAlive属性 ，表示该线程当前是否为可用状态
        //如果线程已经启动，并且当前没有任何异常的话，则是true，否则为false
        //Start()后，线程不一定能马上启动起来，也许CPU正在忙其他的事情，但迟早是会启动起来的！
        if (!isAlive()) {
            return null;
        }

        // If the thread has been started, wait until the looper has been created.
        synchronized (this) {
            while (isAlive() && mLooper == null) {
                try {
                    wait();
                } catch (InterruptedException e) {
                }
            }
        }
        return mLooper;
    }

    @NonNull
    public Handler getThreadHandler() {
        if (mHandler == null) {
            mHandler = new Handler(getLooper());
        }
        return mHandler;
    }

    public boolean quit() {
        Looper looper = getLooper();
        if (looper != null) {
            looper.quit();
            return true;
        }
        return false;
    }

    public boolean quitSafely() {
        Looper looper = getLooper();
        if (looper != null) {
            looper.quitSafely();
            return true;
        }
        return false;
    }

    public int getThreadId() {
        return mTid;
    }
}

public abstract class IntentService extends Service {
    private volatile Looper mServiceLooper;
    private volatile ServiceHandler mServiceHandler;
    private String mName;
    private boolean mRedelivery;

    private final class ServiceHandler extends Handler {
        public ServiceHandler(Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) {
            onHandleIntent((Intent)msg.obj);
            stopSelf(msg.arg1);
        }
    }

    public IntentService(String name) {
        super();
        mName = name;
    }

    public void setIntentRedelivery(boolean enabled) {
        mRedelivery = enabled;
    }

    @Override
    public void onCreate() {
        // TODO: It would be nice to have an option to hold a partial wakelock
        // during processing, and to have a static startService(Context, Intent)
        // method that would launch the service & hand off a wakelock.

        super.onCreate();
        HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
        thread.start();

        mServiceLooper = thread.getLooper();
        mServiceHandler = new ServiceHandler(mServiceLooper);
    }

    @Override
    public void onStart(@Nullable Intent intent, int startId) {
        Message msg = mServiceHandler.obtainMessage();
        msg.arg1 = startId;
        msg.obj = intent;
        mServiceHandler.sendMessage(msg);
    }

    @Override
    public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
        onStart(intent, startId);
        return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
    }

    @Override
    public void onDestroy() {
        mServiceLooper.quit();
    }

    @Override
    @Nullable
    public IBinder onBind(Intent intent) {
        return null;
    }

    @WorkerThread
    protected abstract void onHandleIntent(@Nullable Intent intent);
}

class IntentServiceDemo : IntentService("IntentServiceDemo") {
    private val TAG = "zmm"

    /* (non-Javadoc)
     * @see android.app.IntentService#onCreate()
     */
    override fun onCreate() {
        Log.e(TAG, "=>onCreate")
        super.onCreate()
    }

    override fun onStartCommand(@Nullable intent: Intent?, flags: Int, startId: Int): Int {
        Log.e(TAG, "=>onStartCommand")
        return super.onStartCommand(intent, flags, startId)
    }

    /* (non-Javadoc)
         * @see android.app.IntentService#onDestroy()
         */
    override fun onDestroy() {
        Log.e(TAG, "=>onDestroy")
        super.onDestroy()
    }

    override fun onHandleIntent(arg0: Intent?) {
        try {
            Log.e(TAG, "IntentService 线程：" + Thread.currentThread().id)
            Thread.sleep(2000)
        } catch (e: InterruptedException) {
            e.printStackTrace()
        }

    }
}

var mServiceIntent = Intent(this@MainActivity, IntentServiceDemo::class.java)
        startService(mServiceIntent)