先上程式碼：

public class MyService extends Service {
    public MyService() {
    }

    private long mServiceCreatTime;


    @Override
    public void onCreate() {
        super.onCreate();
        mServiceCreatTime = System.currentTimeMillis();
    }

    @Override
    public IBinder onBind(Intent intent) {
        return
 
 new MyBinder();
    }

    public class MyBinder extends Binder{
        public String getRunningTime(){
            return MyService.this.getRunningTime();
        }
    }

    public String getRunningTime(){
        long runningTime = System.currentTimeMillis()-mServiceCreatTime;
        return String.format("服務已執行: %s"
 
,dateFormat(runningTime));
    }

    public String dateFormat(long timeMillions){
        Date date = new Date(timeMillions);
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
        return sdf.format(date);
    }

}

public class MainActivity extends AppCompatActivity {

    private
 
 TextView mTvRunningTime;
    private MyService.MyBinder mMyBinder;

    private Handler mHandler = new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mTvRunningTime = (TextView) findViewById(R.id.tv_running_time);

        //繫結服務
        Intent intent = new Intent(this,MyService.class);
        MyServiceConnection myServiceConnection = new MyServiceConnection();
        bindService(intent,myServiceConnection, Context.BIND_AUTO_CREATE);

        refreshRunningTime();
    }

    private void refreshRunningTime(){
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                mHandler.post(new Runnable() {
                    @Override
                    public void run() {
                        //通過MyBinder呼叫MyService中的getRunningTime()方法
                        if (mMyBinder!=null) {
                            mTvRunningTime.setText(mMyBinder.getRunningTime());
                        }
                    }
                });
            }
        },0,1000);
    }

    private class MyServiceConnection implements ServiceConnection{

        @Override
        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
            mMyBinder = (MyService.MyBinder) iBinder;
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {

        }
    }

}

實現步驟：
1.在Service中建立一個Binder的子類MyBinder， 在MyBinder中呼叫MyService需要提供給外部呼叫的getRuuningTime()方法；
2.在MyService的onBind（）方法中返回MyBinder的例項；
3.在Activity中建立一個ServiceConnection的實現類MyServiceConnection;
4.通過bindService（）啟動MyService;
5.在MyServiceConnection的onServiceConnected（）方法中將iBinder強轉為MyBinder, 這樣就可以通過MyBinder呼叫MyService中的getRunningTime()方法了。