QObject::startTimer: Timers can only be used with threads started with QThread

问题：
qt程序报错：QObject::startTimer: Timers can only be used with threads started with QThread

原因：
定时器启动函数startTimer的调用操作必须是在main函数中app定义的后面，如下：

    QGuiApplication app(argc, argv);
	// 定时器启动函数必须在app后调用
	timer.startTimer(3000);