我如何在android中通话时启动服务

Question

    public class CustomPhoneStateListener extends PhoneStateListener {

    //private static final String TAG = "PhoneStateChanged";
    Context context; //Context to make Toast if required
    public CustomPhoneStateListener(Context context) {
        super();
        this.context = context;
    }

    @Override
    public void onCallStateChanged(int state, String incomingNumber) {
        super.onCallStateChanged(state, incomingNumber);

        switch (state) {
            case TelephonyManager.CALL_STATE_IDLE:
                //when Idle i.e no call
                Toast.makeText(context, "Phone state Idle", Toast.LENGTH_LONG).show();
                break;
            case TelephonyManager.CALL_STATE_OFFHOOK:
                //when Off hook i.e in call
                //Make intent and start your service here
                Intent intent= new Intent();

                break;
            case TelephonyManager.CALL_STATE_RINGING:
                //when Ringing
                Toast.makeText(context, "Phone state Ringing", Toast.LENGTH_LONG).show();
                break;
            default:
                break;
        }
    }

我有一个实现浮动小部件的服务，仅当有人打来电话时，我如何启动该服务