windows 文件的拖放是如何完成的？
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How drag and drop of files is done?
提问by kasperasky
as in winamp or vlc player, how to do a file drag and drop? i mean i want to know what sort of coding goes into application? i want to know for c++
就像在 winamp 或 vlc 播放器中一样，如何进行文件拖放？我的意思是我想知道什么样的编码进入应用程序？我想知道 C++
回答by Eli Bendersky
In pure C/C++ on Windows, start reading about the DragAcceptFilesfunction and the WM_DROPFILESmessage. If you're using a more powerful C++ library (Qt, Wx, etc) check their respective documentation. It would help to know what you use, more specifically.
在 Windows 上的纯 C/C++ 中，开始阅读DragAcceptFiles函数和WM_DROPFILES消息。如果您使用更强大的 C++ 库（Qt、Wx 等），请查看它们各自的文档。更具体地说，了解您使用的是什么会有所帮助。
Also, this discussionmay answer your question. If it's what you meant, please close this question.
此外，此讨论可能会回答您的问题。如果这是你的意思，请关闭这个问题。
回答by no_ripcord
With com:
与 com：
Create a class that public extends IDropTarget
创建一个公共扩展 IDropTarget 的类
Register your class for drops. Do this in WM_CREATE
注册您的课程以获取滴剂。在 WM_CREATE 中执行此操作
RegisterDragDrop(hwnd,static_cast<IDropTarget*>(pointer_to_your_class));
In your class you need to override a couple of functions since they are pure virtual:
在您的课程中，您需要覆盖几个函数，因为它们是纯虚拟的：
virtual HRESULT STDMETHODCALLTYPE DragEnter(
/* [unique][in] */ __RPC__in_opt IDataObject *pDataObj,
/* [in] */ DWORD grfKeyState,
/* [in] */ POINTL pt,
/* [out][in] */ __RPC__inout DWORD *pdwEffect) = 0;
virtual HRESULT STDMETHODCALLTYPE DragOver(
/* [in] */ DWORD grfKeyState,
/* [in] */ POINTL pt,
/* [out][in] */ __RPC__inout DWORD *pdwEffect) = 0;
virtual HRESULT STDMETHODCALLTYPE DragLeave( void) = 0;
virtual HRESULT STDMETHODCALLTYPE Drop(
/* [unique][in] */ __RPC__in_opt IDataObject *pDataObj,
/* [in] */ DWORD grfKeyState,
/* [in] */ POINTL pt,
/* [out][in] */ __RPC__inout DWORD *pdwEffect) = 0;
Each of those functions will get called when those events occur, i.e. when someone pass the mouse in your window with a file DragEnter on your class will get called.
当这些事件发生时，这些函数中的每一个都会被调用，即当有人在你的窗口中传递鼠标时，你的类上的文件 DragEnter 将被调用。
You will also need to implement a couple more functions that IDropTarget extends, check out IUnknown in your MSDN.
您还需要实现 IDropTarget 扩展的更多功能，请查看 MSDN 中的 IUnknown。
Then you need to query IDataObject param to get the data:
然后你需要查询 IDataObject 参数来获取数据：
FORMATETC fdrop = {CF_HDROP, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL};
if (SUCCEEDED(pDataObj->QueryGetData(&fdrop)) ){
STGMEDIUM stgMedium = {0};
stgMedium.tymed = TYMED_HGLOBAL;
HRESULT hr = pDataObj->GetData(&fdrop, &stgMedium);
if (SUCCEEDED(hr))
{
HGLOBAL gmem = stgMedium.hGlobal;
HDROP hdrop = (HDROP)GlobalLock(gmem);
UINT numOfFiles = DragQueryFile( (HDROP) hdrop,
0xFFFFFFFF,
NULL,
0
);
TCHAR buffer[MAX_PATH];
for( int i=0;i<numOfFiles;i++ ){
UINT charsCopied = DragQueryFile( (HDROP) hdrop,
i,
buffer,
MAX_PATH
);
MessageBox(NULL,buffer,_T("Archivos a copiar: "),MB_OK);
}
// use str
GlobalUnlock(gmem);
/*TCHAR* str = (TCHAR*)GlobalLock(gmem);
// use str
GlobalUnlock(gmem);*/
::ReleaseStgMedium(&stgMedium);
}
}
Cheers!
干杯!
回答by Marc Gravell
editafterI posted this, the question was edited to qualify as C++; I'm going to leave this answer here for reference only.
编辑后，我贴这个，这个问题是编辑资格作为C ++; 我将把这个答案留在这里仅供参考。
"what sort off coding goes into application":
“什么样的编码进入应用程序”：
That depends hugely on the platform and language. For example, here are examples for Windows via C#/.NETor VB/.NET. For C++, Delphi, etc - the tricks will be different.
这在很大程度上取决于平台和语言。例如，这里是通过C#/.NET或VB/.NET 的Windows 示例。对于 C++、Delphi 等 - 技巧会有所不同。
回答by Vinay
You should use COM's Ole Drag and drop interfaces.
您应该使用 COM 的 Ole 拖放界面。
回答by Ferruccio
Before the days of OLE/COM/ActiveX, we would do something like the following:
在 OLE/COM/ActiveX 出现之前，我们会做如下的事情：
- If we received a mouse down event, take note of cursor position.
- If we received a mouse movement and it moved a certain distance from the original point then we're starting a drag operation. Build a cursor that represents the object you're dragging (determined from the original cursor position).
- When we received a mouse down: if dragging never started then it's a click otherwise use the drop position to determine what to do with the object.
- 如果我们收到鼠标按下事件，请注意光标位置。
- 如果我们收到鼠标移动并且它从原点移动了一定距离，那么我们开始拖动操作。构建一个表示您正在拖动的对象的光标（根据原始光标位置确定）。
- 当我们收到鼠标按下时：如果拖动从未开始，那么它是点击，否则使用放置位置来确定如何处理对象。
Note: none of this would allow you to drag objects between apps, just inside individual apps.
注意：这些都不允许您在应用程序之间拖动对象，只能在单个应用程序内拖动。
