之前研究過handler 和 looper 消息隊列,不過Android裡的handler不是另外開啟線程來執行的,還是在主UI線程中,如果想另啟線程的話需要用到HandlerThread來實現。在使用HandlerThread的時候需要實現CallBack接口以重寫handlerMessage方法,在handlerMessage方法中來處理自己的邏輯。下來給出一個小例子程序。
layout文件很簡單,就一個按鈕來啟動HanlderTread線程
- <?xml version="1.0" encoding="utf-8"?>
- <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:orientation="vertical" >
-
- <TextView
- android:layout_width="fill_parent"
- android:layout_height="wrap_content"
- android:text="@string/hello" />
-
- <Button
- android:id="@+id/handlerThreadBtn"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:text="startHandlerThread" />
-
- </LinearLayout>
Activity代碼如下:
- package com.tayue;
-
- import android.app.Activity;
- import android.os.Bundle;
- import android.os.Handler;
- import android.os.Handler.Callback;
- import android.os.HandlerThread;
- import android.os.Message;
- import android.view.View;
- import android.view.View.OnClickListener;
- import android.widget.Button;
- /**
- *
- * @author xionglei
- *
- */
- public class TestHandlerActivity extends Activity implements OnClickListener{
-
- public Button handlerThreadBTN;
- MyHandlerThread handlerThread;
- Handler handler;
-
- /** Called when the activity is first created. */
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- //打印UI線程的名稱
- System.out.println("onCreate CurrentThread = " + Thread.currentThread().getName());
-
- setContentView(R.layout.main);
-
- handlerThreadBTN = (Button) findViewById(R.id.handlerThreadBtn);
- handlerThreadBTN.setOnClickListener(this);
-
- handlerThread = new MyHandlerThread("myHanler");
- handlerThread.start();
- //注意: 這裡必須用到handler的這個構造器,因為需要把callback傳進去,從而使自己的HandlerThread的handlerMessage來替換掉Handler原生的handlerThread
- handler = new Handler(handlerThread.getLooper(), handlerThread);
-
-
- }
-
- @Override
- public void onClick(View v) {
- //點擊按鈕後來開啟線程
- handler.sendEmptyMessage(1);
- }
-
-
- private class MyHandlerThread extends HandlerThread implements Callback {
-
- public MyHandlerThread(String name) {
- super(name);
- }
-
- @Override
- public boolean handleMessage(Message msg) {
- //打印線程的名稱
- System.out.println(" handleMessage CurrentThread = " + Thread.currentThread().getName());
- return true;
- }
-
-
- }
-
-
-
-
- }
點擊按鈕,打印的日志如下(這裡點擊了3次)
07-06 09:32:48.776: I/System.out(780): onCreate CurrentThread = main
07-06 09:32:55.076: I/System.out(780): handleMessage CurrentThread = myHanler
07-06 09:32:58.669: I/System.out(780): handleMessage CurrentThread = myHanler
07-06 09:33:03.476: I/System.out(780): handleMessage CurrentThread = myHanler
HandlerThread就這麼簡單。
當然 android自己也有異步線程的handler,就是AsyncTask,這個類就是封裝了HandlerThread 和handler來實現異步多線程的操作的。