因為源碼很簡短，這裏就全部粘貼過來了。

/**

• Handy class for starting a new thread that has a looper. The looper can then be

• used to create handler classes. Note that start() must still be called.
  */
  public class HandlerThread extends Thread {
  int mPriority;
  int mTid = -1;
  Looper mLooper;
  private @Nullable Handler mHandler;

  public HandlerThread(String name) {
  super(name);
  // 使用的是 Process 的優先級
  mPriority = Process.THREAD_PRIORITY_DEFAULT;
  }

  /**

  • Constructs a HandlerThread.
  • @param name
  • @param priority The priority to run the thread at. The value supplied must be from
  • {@link android.os.Process} and not from java.lang.Thread.
    */
    public HandlerThread(String name, int priority) {
    
    super(name);
    mPriority = priority;
    }

  /**

  • Call back method that can be explicitly overridden if needed to execute some
  • setup before Looper loops.
    */
    protected void onLooperPrepared() {
    }

  // 重點就是在這個 run 方法中，這裏Android 系統幫我們進行了 Looper.prepare 和 Looper.loop,如果在執行耗時操作之前，我們需要進行一些其他的初始化，可以繼承 onLooperPrepared()@Override
  

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

  /**

  • This method returns the Looper associated with this thread. If this thread not been started
  • or for any reason isAlive() returns false, this method will return null. If this thread
  • has been started, this method will block until the looper has been initialized.

  • @return The looper.
    */
    public Looper getLooper() {
    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;
    }

  /**

  • @return a shared {@link Handler} associated with this thread
  • @hide*/
    @NonNull
    br/>*/
    @NonNull
    if (mHandler == null) {
    mHandler = new Handler(getLooper());
    }
    return mHandler;
    }

  /**

  • Quits the handler thread‘s looper.
  • <p>
  • Causes the handler thread‘s looper to terminate without processing any
  • more messages in the message queue.
  • </p><p>
  • Any attempt to post messages to the queue after the looper is asked to quit will fail.
  • For example, the {@link Handler#sendMessage(Message)} method will return false.
  • </p><p class="note">
  • Using this method may be unsafe because some messages may not be delivered
  • before the looper terminates. Consider using {@link #quitSafely} instead to ensure
  • that all pending work is completed in an orderly manner.
  • </p>
  • @return True if the looper looper has been asked to quit or false if the
  • thread had not yet started running.
  • @see #quitSafely
    */
    public boolean quit() {
    Looper looper = getLooper();
    if (looper != null) {
    looper.quit();
    return true;
    }
    return false;
    }

  /**

  • Quits the handler thread‘s looper safely.
  • <p>
  • Causes the handler thread‘s looper to terminate as soon as all remaining messages
  • in the message queue that are already due to be delivered have been handled.
  • Pending delayed messages with due times in the future will not be delivered.
  • </p><p>
  • Any attempt to post messages to the queue after the looper is asked to quit will fail.
  • For example, the {@link Handler#sendMessage(Message)} method will return false.
  • </p><p>
  • If the thread has not been started or has finished (that is if
  • {@link #getLooper} returns null), then false is returned.
  • Otherwise the looper is asked to quit and true is returned.
  • </p>
  • @return True if the looper looper has been asked to quit or false if the
  • thread had not yet started running.
    */
    public boolean quitSafely() {
    Looper looper = getLooper();
    if (looper != null) {
    looper.quitSafely();
    return true;
    }
    return false;
    }

  /**

  • Returns the identifier of this thread. See Process.myTid().
    */
    public int getThreadId() {
    return mTid;
    }
    }

HandlerThread 特點和北京pk10源碼搭建解析