android - 只有一个线程实例在服务中

Question

我在服务中初始化了新线程，但是当我开始服务时，新的线程被创建并且它使我的应用程序崩溃，因为我在其中使用了相机。如何使它成为该线程的唯一一个实例？

线程何时关闭？如果我关闭我制作的服务，它也会被关闭吗？

Answer 1

您可以使用锁或静态变量：

private static boolean isThreadRunning;

然后为您服务：

if(isThreadRunning)
   return;

Thread t=new Thread(new Runnable(){

protected void run(){
   isThreadRunning=true;
   while(yourcondition){
     //your thread code...
   }
   isThreadRunning=false;
   //if you want to start another thread after this one is ended, you should post a message to a handler here and it should start another thread like this
}

});

Answer 2

您也可以使用Handler类来实现这一点，这是谷歌在线程操作中推荐的。下面的代码显示了如何在Service.

public class MyService extends Service{


    private final Handler handler = new Handler();

    private final static int RUNABLE_WHAT=6558057;
    private final static int PEROID=6*1000;
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        if(!handler.hasMessages(RUNABLE_WHAT))
        {
            handler.sendMessageDelayed(new Worker().extractMessage(), PEROID);
        }
        return START_STICKY;
    }

    private class Worker implements Runnable{

        @Override
        public void run() {
            //DO WORK HERE
            handler.sendMessageDelayed(new Worker().extractMessage(), PEROID);
        }
        private Message extractMessage()
        {
            Message message = Message.obtain(handler, this);
            message.what=RUNABLE_WHAT;
            return message;
        }
    }


}