Handler類別

使不同Thread溝通的機制，將Thread要傳遞的訊息放入Message類別，透過Handler與另一個Thread溝通，讓另一個Thread從類別取得訊息

class MainActivity : AppCompatActivity(){
	//Step1:建立Handler物件接受訊息
	private val handler = Handler(Looper.getMainLooper()) { msg ->
		when (msg.what) { //判斷msg的編號
			1 -> {
				//執行於Main Thread
			}
		}
		return@Handeler true
	}

	override fun onCreate(savedInstanceState: Bundle?){
		super.onCreate(savedInstanceState)
		setContentView(R.layout.activity_main)
		Thread{
			//執行於Background Thread
			//Step2:建立Message物件並加入編號
			val msg = Message()
			msg.what = 1
			//Step3:透過sendMessage傳送訊息
			handler.sendMessage(msg)
		}.start()
	}
}