我需要定期执行一些代码(连接到服务器并每分钟从MySQL数据库中提取数据)。为此,我有一个Sync类:
public class Sync {
static private Handler handler = new Handler();
Runnable task;
public Sync(Runnable task, long time) {
this.task = task;
handler.removeCallbacks(task);
handler.postDelayed(task, time);
}
}
在我的活动中,我有:
public void onCreate(Bundle savedInstanceState) {
...
Sync sync = new Sync(call,60*1000);
...
}
final private Runnable call = new Runnable() {
public void run() {
//This is where my sync code will be, but for testing purposes I only have a Log statement
Log.v("test","this will run every minute");
}
};
我已经用较短的测试时间尝试过这个方法,但它只运行一次。当它第一次记录消息时,也是最后一次。有没有人看到我在这里做什么?谢谢!
发布于 2012-04-18 18:44:34
你可以使用下面的代码来做到这一点,希望它能有所帮助!
final Handler handler = new Handler();
Runnable runnable = new Runnable() {
@Override
public void run() {
try{
//do your code here
}
catch (Exception e) {
// TODO: handle exception
}
finally{
//also call the same runnable to call it at regular interval
handler.postDelayed(this, 1000);
}
}
};
//runnable must be execute once
handler.post(runnable);
发布于 2012-04-18 18:53:23
首先,你必须声明全局的处理程序;其次,你必须在runnable中再次使用post延迟方法来再次触发它。
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Sync sync = new Sync(call,60*1000);
}
final private Runnable call = new Runnable() {
public void run() {
//This is where my sync code will be, but for testing purposes I only have a Log statement
Log.v("test","this will run every minute");
handler.postDelayed(call,60*1000);
}
};
public final Handler handler = new Handler();
public class Sync {
Runnable task;
public Sync(Runnable task, long time) {
this.task = task;
handler.removeCallbacks(task);
handler.postDelayed(task, time);
}
}
}
发布于 2012-04-18 18:45:46
handler.postDelayed(task, time);
只执行一次,如果你想让代码定期触发,我建议使用Timer
和TimerTask
,而不是Handler
和Runnable
。
TimerTasks
可以设置为运行一次,每x秒运行一次,或者以固定的周期运行,例如x秒-无论上次运行花费了多长时间。
https://stackoverflow.com/questions/10207612
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