android中Handler简介&利用Handler实现计时功能
Handler为android系统的线程通信工具，承担着主线程与分线程，分线程之间的通信功能，经常用到的有post()，sendMessage() 方法，前者是将一个线程加入线程队列，后者是发送一个消息到消息队列中，post方法还有两个变种，分别为定时发送postAtTime()和延时发送postDelayed()。计时功能的实现主要利用了postDelayed()函数，即在run函数中以一秒为延时，不断调用自身，直到外部结束线程。代码如下：
public class HandlerDemoActivity extends Activity { /** Called when the activity is first created. */ Count count; int i = 0;@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); count = new Count(); handler.post(count); } class Count implements Runnable{ @Override public void run() { Log.i("count",String.valueOf(i++)); handler.postDelayed(count, 1000); } }; final Handler handler = new Handler(){ @Override public void handleMessage(Message msg) { super.handleMessage(msg); } };}
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