创建一个 Looper 线程

方法一：创建一个 Thread 线程

1. MainActivity.kt 内的 onCreate() 最后添加：

           val looperThread = LooperThread()
           looperThread.start()
   
           thread {
               Thread.sleep(3000)
               val message = Message()
               message.what = LooperThread.EVENT_INIT
               message.target = looperThread.getHandler()
               Log.d(
                   "MainActivity",
                   "send message ${message.what} at thread id ${Thread.currentThread().id}"
               )
               message.sendToTarget()
           }

2. 新建 LooperThread.kt：

   package com.example.myapplication
   
   import android.os.Handler
   import android.os.Looper
   import android.os.Message
   import android.util.Log
   
   
   class LooperThread : Thread() {
       private var handler: Handler? = null
       private var isInitialized = false
   
   
       fun getHandler(): Handler? {
           return handler
       }
   
       override fun run() {
           Looper.prepare()
           handler = object : Handler(Looper.myLooper()!!) {
               override fun handleMessage(msg: Message) {
                   Log.d(
                       TAG,
                       "Received message ${msg.what} at thread id ${
                           currentThread().id
                       }"
                   )
                   when (msg.what) {
                       EVENT_INIT -> {
                           performInit()
                       }
                       else -> println("Unknown Event: " + msg.what)
                   }
               }
           }
           isInitialized = true
           Looper.loop()
       }
   
       fun isInitialized(): Boolean {
           return isInitialized
       }
   
       private fun performInit() {
           Log.d(TAG, "performInit() called")
           sleep(1000);
       }
   
       companion object {
           const val EVENT_INIT: Int = 1
           private const val TAG = "LooperThread"
       }
   }

方法二：创建一个 HandlerThread 线程

1. MainActivity.kt 内的 onCreate() 最后添加：

           val myHandlerThread = MyHandlerThread("MyHandlerThreadA")
           myHandlerThread.start()
   
           thread {
               Thread.sleep(3000)
               val message = Message()
               message.what = MyHandlerThread.EVENT_INIT
               message.target = myHandlerThread.handler
               Log.d(
                   "MainActivity",
                   "send message ${message.what} at thread id ${Thread.currentThread().id}"
               )
               message.sendToTarget()
           }

2. 新建 MyHandlerThread.kt：

   package com.example.myapplication
   
   import android.os.Handler
   import android.os.HandlerThread
   import android.os.Looper
   import android.os.Message
   import android.util.Log
   
   public class MyHandlerThread(name: String?) : HandlerThread(name) {
       lateinit var handler: Handler;
   
       override fun onLooperPrepared() {
           super.onLooperPrepared()
           handler = object : Handler(Looper.myLooper()!!) {
               override fun handleMessage(msg: Message) {
                   Log.d(
                       TAG,
                       "Received message ${msg.what} at thread id ${
                           currentThread().id
                       }"
                   )
                   when (msg.what) {
                       EVENT_INIT -> performInit()
                       else -> println("Unknown Event: " + msg.what)
                   }
               }
           }
       }
   
   
       private fun performInit() {
           Log.d(TAG, "performInit() called")
           sleep(1000);
       }
   
       companion object {
           const val EVENT_INIT: Int = 1
           private const val TAG = "MyHandlerThread"
       }
   }