我用win32 API DoDragDrop 实现脱放，调用DoDragDrop时出现非法地址访问

ondarkness 2011-11-30 05:48:46

我自己实现了IDataObject，IDropSource

FORMATETC fmtetc = {CF_UNICODETEXT, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL};
STGMEDIUM stgmed = {TYMED_HGLOBAL, {0}, 0};
stgmed.hGlobal = StringToHandle (L"Hello, World!", -1);

if (CreateDataObject(&fmtetc, &stgmed, 1, &pDataObject) != S_OK)
{
return FALSE;
}
if( CreateDropSource(&pDropSource) != S_OK )
{
return FALSE;
}
DWORD dwResult = DoDragDrop(pDataObject,pDropSource,DROPEFFECT_MOVE|DROPEFFECT_COPY,&dwEffect);
if( dwResult == DRAGDROP_S_DROP )
{
if( dwEffect == DROPEFFECT_MOVE )
{
}
}
pDropSource->Release();
pDataObject->Release();
ReleaseStgMedium(&stgmed);

我准备好了，IDataObject对象，和IDropSource对象，然后调用 DoDragDrop，如上所示，但是一旦我松开鼠标左键，DoDragDrop便会出现非法地址访问，但那句“hello world”确实传递成功了，鼠标释放时，所在窗口里显示了“hello world”。

不知哪里除了问题？

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fishion 2011-12-01

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不调用后面三句有异常吗
pDropSource->Release();
pDataObject->Release();
ReleaseStgMedium(&stgmed);

ondarkness 2011-12-01

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有没有示例代码啊，用WIN32 API实现的，不是MFC的，有代码的话，应该能找到问题。

ondarkness 2011-12-01

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在
DWORD dwResult = DoDragDrop(pDataObject,pDropSource,DROPEFFECT_MOVE|DROPEFFECT_COPY,&dwEffect);
这里就崩溃了，字符串确实传递过去了。

DoDragDrop使用方法，用于开始对象的拖放操作

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/// 工作区坐标 /// public ListViewItem GetNearItem(Point ClientPoint) { ListViewItem lvt = this.GetItemAt(ClientPoint.X, ClientPoint.Y); if (lvt != null) return lvt; List vt = new List(); for (int i = 1; i < 10; i++) { lvt = this.GetItemAt(ClientPoint.X, ClientPoint.Y + i); if (lvt != null) vt.Add(lvt); lvt = this.GetItemAt(ClientPoint.X, ClientPoint.Y - i); if (lvt != null) vt.Add(lvt); lvt = this.GetItemAt(ClientPoint.X + i, ClientPoint.Y); if (lvt != null) vt.Add(lvt); lvt = this.GetItemAt(ClientPoint.X + i, ClientPoint.Y + i); if (lvt != null) vt.Add(lvt); lvt = this.GetItemAt(ClientPoint.X + i, ClientPoint.Y - i); if (lvt != null) vt.Add(lvt); lvt = this.GetItemAt(ClientPoint.X - i, ClientPoint.Y); if (lvt != null) vt.Add(lvt); lvt = this.GetItemAt(ClientPoint.X - i, ClientPoint.Y + i); if (lvt != null) vt.Add(lvt); lvt = this.GetItemAt(ClientPoint.X - i, ClientPoint.Y - i); if (lvt != null) vt.Add(lvt); if (vt.Count > 0) break; } if (vt.Count == 0) { return null; } else if (vt.Count == 1) { return vt[0]; } else { double HisDis = 0; int i = 0; foreach (ListViewItem item in vt) { double dis = GetDistince(ClientPoint, item.Position); if (i == 0 || dis < HisDis) { lvt = item; HisDis = dis; } i++; } return lvt; } } ///

/// 两点间的距离 ///

/// 起点 /// 终点 /// private double GetDistince(Point start, Point end) { double distince2 = Math.Pow((start.X - end.X), 2) + Math.Pow((start.Y - end.Y), 2); return Math.Abs(Math.Sqrt(distince2)); } } }

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