HandlerThread的简单分析

Posted 2021-01-13 xiongbo753

一.简介

HanlerThread就是一个封装了Loop的Thread，其他线程能够通过创建Handler传进去该Looper，与HandlerThread通信

二.源码分析

  1.因为其是一个Thread，所以可以从run方法看起

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

该代码就是创建一个Looper，onLooperPrepared() ---是Looper实现之前的准备工作，我们可以重写它来实现自己的逻辑

2.getLooper() 方法

 /**
     * 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;
    }

该代码表明，如果需要获取到Looper，那么Thread一定需要先启动。

3.getThreadHandler()

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

该方法主要是获取用 mLooper创建的Handler，其他线程可以获取它来进行通信

三.具体实现