使用处理程序从服务更新活动的ui而不调用oncreate（）和start（）服务的命令

我使用处理程序从服务中更新UI或每15秒显示活动类，所以我在活动中定义了处理程序对象，并使用服务程序中的处理程序方法MainActivity.handler.sendemptymessage（）从服务类中更新UI或每15秒显示敬酒中，但是什么当我启动服务时，单击服务类的oncreate（）按钮时没有发生像创建服务那样向我显示吐司的情况，也没有显示onStartCommand吐司，并且仅一次没有显示活动类的吐司，所以，在我的以下代码中出了什么问题我在活动类中定义处理程序对象的正确方法，我不知道请给我适当的解决方案。我知道其他组件可以将ui从服务更新为活动，但是我只想通过handler和sendemptymessage.thanks提前实现

MainActivity->

public class MainActivity extends ActionBarActivity {
    static Activity thisActivity = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button b1 = (Button) findViewById(R.id.button1);
        Button b2 = (Button) findViewById(R.id.button2);
        thisActivity = this;


        b1.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                startService(new Intent(MainActivity.this, ServiceDemo.class));
            }
        });

        b2.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                stopService(new Intent(MainActivity.this, ServiceDemo.class));
            }

        });

    }

    static Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {

            // This is where main activity thread receives messages
            // Put here your handling of incoming messages posted by other
            // threads
            super.handleMessage(msg);

            if (msg.what == 0) {

                show();
            }
        }

    };

    public static void show() {

        Toast.makeText(thisActivity, "recive called", Toast.LENGTH_SHORT)
                .show();

    }

}

Service.class- >

public class ServiceDemo extends Service {
    int mStartMode;
    /** interface for clients that bind */
    IBinder mBinder;
    /** indicates whether onRebind should be used */
    boolean mAllowRebind;

    /** Called when the service is being created. */
    @Override
    public void onCreate() {
        Toast.makeText(getApplicationContext(), " service created",
                Toast.LENGTH_SHORT).show();
    }

    /** The service is starting, due to a call to startService() */
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        Toast.makeText(getApplicationContext(), "service started",
                Toast.LENGTH_SHORT).show();
        while (true) {
            try {
                Thread.sleep(15000);
                MainActivity.handler.sendEmptyMessage(0);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return mStartMode;
        }

    }

    /** A client is binding to the service with bindService() */
    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    /** Called when all clients have unbound with unbindService() */
    @Override
    public boolean onUnbind(Intent intent) {
        return mAllowRebind;
    }

    /** Called when a client is binding to the service with bindService() */
    @Override
    public void onRebind(Intent intent) {

    }

    /** Called when The service is no longer used and is being destroyed */
    @Override
    public void onDestroy() {
        Toast.makeText(getApplicationContext(), "service destroyed",
                Toast.LENGTH_SHORT).show();
    }
}