我被要求在我的项目中集成网络摄像头 ZoneTrigger。站点中提供的 SDK 也是 C++ 示例。我已经能够使用一些功能。我被卡住的地方是完成回调的函数。 示例c++中的回调函数代码
ZT_SetCallbackProc(ZoneTriggerCallbackProc);
//在头文件中
typedef int (WINAPI *f_ZT_SetCallbackProc) (void *proc);
/*
Sets up the callback function for your application.
The proc should be declared like this:
int WINAPI ZoneTriggerCallbackProc(int MessageType, ZT_TRIG_STRUCT *trigInfo);
MessageType may be one of the following:
0: Zone Trigger sends a trig. The trigInfo contains data about the hot spots that generated the trig.
1: Zone Trigger has started and is notifying us that it is ready. This only occurs when Zone Trigger starts after the interface DLL is loaded.
2: Zone Trigger is shutting down. You application may need to know this. If Zone Trigger is started again, your application will get message 1.
3: Zone Trigger's Hot spot scheme has changed (a Hot Spot was added or deleted)
*/
我的 C# 代码:
[DllImport("ZTcom.dll")]
private static extern IntPtr ZT_SetCallbackProc(int ZoneTriggerCallbackProc);
private unsafe int ZoneTriggerCallbackProc(int MessageType, ref ZT_TRIG_STRUCT trigInfo)
{
switch (MessageType)
{
case 0: //Trig from a Zone Trigger hot spot
// string s1 = new string(trigInfo.SpotName);
MessageBox.Show("Got a trig from spot" + trigInfo.SpotIndex.ToString()+ s1 );
break;
case 1: //Zone Trigger has started and is notifying us that it is ready
MessageBox.Show("Zone Trigger issued a ready notification.\r\n");
break;
case 2: //Zone Trigger is shutting down
MessageBox.Show("Zone Trigger has left the building.\r\n");
break;
case 3: //Hot spot scheme updated, you might want yo re-enumerate the hot spots
MessageBox.Show("Zone Trigger's hot spots have been updated.\r\n");
break;
}
return 0;
}
到目前为止我已经达到...但是我不明白如何调用 ZT_SetCallbackProc 函数?
IntPtr tg = IntPtr.Zero;
tg = ZT_SetCallbackProc(ZoneTriggerCallbackProc);
这给出了 ZoneTriggerCallbackProc 是一个方法组的错误。请帮忙...提前致谢。
最佳答案
丹尼尔的 answer有简单快捷的路线。如果您不想遇到问题(因为委托(delegate)可能会被 GC 收集并导致 AccessViolationException),您将需要执行以下操作。
Daniel 的类型/pinvoke 声明(为了完整性):
// int WINAPI ZoneTriggerCallbackProc(int MessageType, ZT_TRIG_STRUCT *trigInfo);
delegate int ZoneTriggerCallbackProc(int messageType, ref ZT_TRIG_STRUCT trigInfo);
[DllImport("ZTcom.dll")]
private static extern IntPtr ZT_SetCallbackProc(ZoneTriggerCallbackProc callbackProc);
在您的包装类中,保留对委托(delegate)的引用,以便 GC 在设置回调时不会收集委托(delegate)。
public class ZoneTrigger : CriticalFinalizerObject
{
private ZoneTriggerCallbackProc _zoneTriggerCallback;
private IntPtr _zoneTriggerCallbackCookie;
public ZoneTrigger()
{
_zoneTriggerCallback = ZoneTriggerCallback;
// Why not just do it here?
_zoneTriggerCallbackCookie = NativeMethods.ZT_SetCallbackProc(_zoneTriggerCallback);
if (_zoneTriggerCallbackCookie == IntPtr.Zero)
throw new Exception("Failed to set callback");
}
private unsafe int ZoneTriggerCallback(int MessageType, ref ZT_TRIG_STRUCT trigInfo)
{
// ...
}
~ZoneTrigger()
{
var oldCookie = Interlocked.Exchange(ref _zoneTriggerCallback, IntPtr.Zero);
if (oldCookie != IntPtr.Zero)
ZT_ClearCallbackProc(oldCookie);
}
}
注意:请接受丹尼尔的回答,这更多是对它的补充。
关于c# - C# 中的非托管 C++ DLL ... WINAPI 和指针,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7318170/