委托调用的问题

[q_forest]

问一个委托的问题
我在一个类里面声明的一个TimerCallback委托变量,然后把他传给一个计时器,如下:

public class SystemPowerManager
    {
        private Timer tmrGetPowerStatus;

        private SYSTEM_POWER_STATUS_EX2 powStatus;

        public TimerCallback GetPowerStatusCallback;

        public SystemPowerManager()
        {
            GetPowerStatusCallback = GetSystemPowerStatus;
            tmrGetPowerStatus = new Timer(GetPowerStatusCallback, powStatus, 0, 2000);
        }

        private void GetSystemPowerStatus(object status)
        {
            NativeMethods.GetSystemPowerStatusEx2(ref powStatus, (uint)Marshal.SizeOf(powStatus), false);
        }
    }

在构造函数里面给委托赋值,然后实例化timer,每隔两秒执行委托.

然后我再一个窗口的Form_Load里面给这个委托添加一个注册方法:
powerManager.GetPowerStatusCallback += headbar.GetBatteryStatusCallback;
GetBatteryStatusCallback是HeadBar类的一个方法.
运行时每次可以调用PowerManager类的GetSystemPowerStatus方法,但是后来注册的方法总是不被执行,这是怎么回事??

[timTrubo]

public SystemPowerManager()
{
GetPowerStatusCallback = GetSystemPowerStatus; <===== ?????
tmrGetPowerStatus = new Timer(GetPowerStatusCallback, powStatus, 0, 2000);
}

powerManager.GetPowerStatusCallback += headbar.GetBatteryStatusCallback <==== ????;

[q_forest]

[Quote=引用 1 楼 的回复:]

public SystemPowerManager()
{
GetPowerStatusCallback = GetSystemPowerStatus; <===== ?????
tmrGetPowerStatus = new Timer(GetPowerStatusCallback, powStatus, 0……
[/Quote]
GetPowerStatusCallback = GetSystemPowerStatus;//初始化委托变量,并注册一个方法

powerManager.GetPowerStatusCallback += headbar.GetBatteryStatusCallback
在别的地方添加一个powerManager的GetPowerStatusCallback委托的方法注册

[q_forest]

难道在SystemPowerManager类外面添加注册方法不行吗?额,我试过在SystemPowerManager类的够构造方法里给GetPowerStatusCallback委托添加一个本类的方法注册,结果是可以调用两个方法.

public SystemPowerManager()
        {
            GetPowerStatusCallback = GetSystemPowerStatus;
            GetPowerStatusCallback += TimerCallbackTest;
            tmrGetPowerStatus = new Timer(GetPowerStatusCallback, powStatus, 0, 2000);
        }

private void TimerCallbackTest(object status)
        {
            System.Threading.Thread.Sleep(1000);
        }

[timTrubo]

       public class A
        {
            public EventHandler myEvent;
            public A()
            {
                this.myEvent += MyMethod;
            }

            public void MyMethod(object sender, EventArgs e)
            {
                Console.WriteLine("A::MyMethod");
            }

            public void Run()
            {
                if (this.myEvent != null)
                {
                    myEvent(this, null);
                }
            }
        }

        public class B
        {
            public B()
            {
            }

            public void MyMethod(object sender, EventArgs e)
            {
                Console.WriteLine("B::MyMethod");
            }
        }


            A a = new A();
            B b = new B();
            a.myEvent += b.MyMethod;
            a.Run();

[q_forest]

多谢pptra了,我在计时器实例化之前注册所有的方法就没问题了,我感觉这个地方不太符合事件的概念,谢谢你的回复