怎么知道Looper是否已经调用quit()成功?

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inner class HandlerThread : Thread() {
private lateinit var mHandler: Handler

override fun run() {
super.run()
        Looper.prepare()
        createHandler()
val msg = Message.obtain()
        msg.what = 1
        mHandler.sendMessage(msg)
        Log.i(tag, "sendMessage: " + currentThread().name)
        Looper.loop()
    }

private fun createHandler() {
mHandler = @SuppressLint("HandlerLeak")
object : Handler() {
override fun handleMessage(msg: Message) {
super.handleMessage(msg)
if (msg.what == 1) {
                    Log.i(tag, "what 1  handleMessage: ${currentThread().name}  ${Looper.myLooper()?.thread?.isAlive}")
                } else {
                    Log.i(tag, "what else  handleMessage: ${currentThread().name}")
                }
                Looper.myLooper()?.quitSafely()
                Log.i(tag, "final  handleMessage: ${currentThread().name}  ${Looper.myLooper()?.isCurrentThread}")
            }
        }


    }

}

实现了一下,用Hnadler子线程给子线程发送消息,课程说,要注意在合适的时机quitSafely(),但是要怎么才能知道Looper是否退出成功,自己试了几个Api,没效果,如上,打印都为true,想问下老师怎么看是否已经退出

默小铭 2020-12-20

源自：Android消息机制与类加载 2-4 Android消息机制之ThreadLocal

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1回答

LovelyChubby 2020-12-21 11:59:56

looper.quit不是有个返回值吗

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提问者默小铭 #1

/**
 * Quits the looper.
 * <p>
 * Causes the {@link #loop} method 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>
 *
 * @see #quitSafely
 */
public void quit() {
    mQueue.quit(false);
}

/**
 * Quits the looper safely.
 * <p>
 * Causes the {@link #loop} method to terminate as soon as all remaining messages
 * in the message queue that are already due to be delivered have been handled.
 * However pending delayed messages with due times in the future will not be
 * delivered before the loop terminates.
 * </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>
 */
public void quitSafely() {
    mQueue.quit(true);
}