将字符串值传递给后台服务

请指导我。感谢您的所有帮助。

我的后台服务正在烤ABC

//-------------------字符串显示文本 = "ABC";-----------------

我有两个字符串，ABC 和 DEF 声明在 mainactivity.java

1. 如何将主活动中的值显示文本传递给此服务。
2. 吐司 ABC 完成后，如何将显示文本更改为 DEF。

我的服务

public class MyService extends Service {
public static final long INTERVAL=3000;//variable to execute services every 5 second
private Handler mHandler=new Handler(); // run on another Thread to avoid crash
private Timer mTimer=null; // timer handling

//获取意图不起作用。我应该把它放在哪里或如何放？

Intent myIntent = getIntent(); 
    if (myIntent !=null && myIntent.getExtras()!=null)
String value = myIntent.getExtras().getString(PassToService);

@Nullable
@Override
public IBinder onBind(Intent intent) {
    throw new UnsupportedOperationException("unsupported Operation");
}
@Override
public void onCreate() {


    // cancel if service is  already existed
    if(mTimer!=null)
        mTimer.cancel();
    else
        mTimer=new Timer(); // recreate new timer
    mTimer.scheduleAtFixedRate(new TimeDisplayTimerTask(),0,INTERVAL);// schedule task

}


    @Override
public void onTaskRemoved(Intent rootIntent) {
    stopSelf();///its will stop service
    super.onTaskRemoved(rootIntent);
}
@Override
public void onDestroy() {
    Toast.makeText(this, "In Destroy", Toast.LENGTH_SHORT).show();//display toast when method called
    mTimer.cancel();//cancel the timer
    super.onDestroy();

}

//inner class of TimeDisplayTimerTask
private class TimeDisplayTimerTask extends TimerTask {
    @Override
    public void run() {

        // run on another thread
        mHandler.post(new Runnable() {
            @Override
            public void run() {
                // display toast at every 10 second
                //String displayingText = "ABC";
                String displayingText = myIntent.getStringExtra("PassToService");
                final Toast Notify = Toast.makeText(getApplicationContext(), displayingText, Toast.LENGTH_SHORT);
                Notify.setGravity(Gravity.CENTER, 0, 0);
                Notify.show();

                Handler cancelToast = new Handler();
                cancelToast.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        Notify.cancel();
                    }
                }, 1000);

            }
        });
    }
}

}