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qyte
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 Posted: Tue Mar 22, 2005 10:42 pm Post subject: Files Dragged into form??? |
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does anyone know if it is possible to enable the drag and drop of files
into a form? and to get the full path name of those files?
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Michel Corbin
Guest
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| Posted: Tue Mar 22, 2005 11:38 pm Post subject: Re: Files Dragged into form??? |
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qyte wrote:
| Quote: | does anyone know if it is possible to enable the drag and drop of files
into a form? and to get the full path name of those files?
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//In the header (*.h) file :
BEGIN_MESSAGE_MAP
MESSAGE_HANDLER(WM_DROPFILES,TMessage,HandleDropFiles) ;
END_MESSAGE_MAP(TForm) ;
// and in the cpp file of the form :
MESSAGE void __fastcall TFpF::HandleDropFiles(TMessage &Message)
{
int nbChar ;
HDROP hDrop=(HDROP)Message.WParam ;
int nbFiles=DragQueryFile(hDrop,-1,NULL,0) ;
char *p ;
for(int i=0;i
{
nbChar=DragQueryFile(hDrop,i,NULL,0) ;
p=new char[nbChar+1] ;
DragQueryFile(hDrop,i,p,nbChar+1) ;
// here do want you want with p
delete[] p ;
}
DragFinish(hDrop) ;
}
hope it helps
Michel
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Remy Lebeau (TeamB)
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| Posted: Tue Mar 22, 2005 11:42 pm Post subject: Re: Files Dragged into form??? |
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"qyte" <gyte (AT) vivodinet (DOT) gr> wrote
| Quote: | does anyone know if it is possible to enable the drag and
drop of files into a form? and to get the full path name of
those files?
|
Of course it is possible. But there is nothing in the VCL to handle that,
so you have to do it manually by accessing the Win32 API directly.
The easiest way is to call DragAcceptFiles() whenever your form
creates/destroys its window handle. Then set up a message handler for the
WM_DROPFILES message, and have it call DragQueryFile() and DragFinish().
Note that this approach is outdated, and provided only for backwards
compatibility. The better way to control file dragging is to implement the
IDropTarget interface instead. Derive a class from IDropTarget and
instantiate it at runtime. Call RegisterDragDrop() and RevokeDragDrop()
when the form creates/destroys its window handle, respectively. Whenever
files are dragged over the window, the IDropTarget::DragEnter() and
IDropTarget::DragOver() methods are called. Use DragEnter() to decide
whether you will accept the files, and DragOver() to let the source know
what kind of operation will be performed when the files are dropped. When
the files are dropped, the IDropTarget::Drop() method is called. In
DragEnter() and Drop(), you are provided with an IDataObject interface that
represents the file's information.
Gambit
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Remy Lebeau (TeamB)
Guest
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| Posted: Wed Mar 23, 2005 12:14 am Post subject: Re: Files Dragged into form??? |
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"Michel Corbin" <"Michel Corbin"> wrote
| Quote: | //In the header (*.h) file :
snip
// and in the cpp file of the form :
snip |
You forgot to show the code that calls DragAcceptFiles(). Without that, the
rest of the code will not run.
Gambit
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qyte
Guest
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| Posted: Wed Mar 23, 2005 6:44 am Post subject: Re: Files Dragged into form??? |
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Michel Corbin wrote:
| Quote: |
qyte wrote:
does anyone know if it is possible to enable the drag and drop of files
into a form? and to get the full path name of those files?
//In the header (*.h) file :
BEGIN_MESSAGE_MAP
MESSAGE_HANDLER(WM_DROPFILES,TMessage,HandleDropFiles) ;
END_MESSAGE_MAP(TForm) ;
// and in the cpp file of the form :
MESSAGE void __fastcall TFpF::HandleDropFiles(TMessage &Message)
{
int nbChar ;
HDROP hDrop=(HDROP)Message.WParam ;
int nbFiles=DragQueryFile(hDrop,-1,NULL,0) ;
char *p ;
for(int i=0;i<nbFiles;++i)
{
nbChar=DragQueryFile(hDrop,i,NULL,0) ;
p=new char[nbChar+1] ;
DragQueryFile(hDrop,i,p,nbChar+1) ;
// here do want you want with p
delete[] p ;
}
DragFinish(hDrop) ;
}
hope it helps
Michel
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i did that and also call DragAcceptFiles(Form1->Handle,true) in the
constructor of the form. The problem is that the files are not accepted.
apart from that there is the following:
[C++ Warning] files.h(239): W8027 Functions containing switch are not
expanded inline
maybe yuo could tell me what am i doing wrong.
just to know i also declared the
MESSAGE void __fastcall TForm1::HandleDropFiles(TMessage &Message)
in the private part of my form.
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qyte
Guest
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| Posted: Wed Mar 23, 2005 7:09 am Post subject: Re: Files Dragged into form??? |
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Remy Lebeau (TeamB) wrote:
The better way to control file dragging is to implement the
| Quote: | IDropTarget interface instead. Derive a class from IDropTarget and
instantiate it at runtime. Call RegisterDragDrop() and RevokeDragDrop()
when the form creates/destroys its window handle, respectively. Whenever
files are dragged over the window, the IDropTarget::DragEnter() and
IDropTarget::DragOver() methods are called. Use DragEnter() to decide
whether you will accept the files, and DragOver() to let the source know
what kind of operation will be performed when the files are dropped. When
the files are dropped, the IDropTarget::Drop() method is called. In
DragEnter() and Drop(), you are provided with an IDataObject interface that
represents the file's information.
Gambit
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Could You be more specific? i have no idea of how to implement
what you say.
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Remy Lebeau (TeamB)
Guest
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| Posted: Wed Mar 23, 2005 7:33 am Post subject: Re: Files Dragged into form??? |
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"qyte" <gyte (AT) vivodinet (DOT) gr> wrote
| Quote: | i did that and also call DragAcceptFiles(Form1->Handle,true)
in the constructor of the form.
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If you call it in the constructor, then don't use the form's global pointer
as it hasn't been assigned yet. Use the implicit 'this' pointer instead,
ie:
DragAcceptFiles(this->Handle, TRUE)
A better place to call it is to override the CreateWnd() and DestroyWnd()
methods, ie:
void __fastcall TForm1::CreateWnd()
{
TForm::CreateWnd();
if( HandleAllocated() )
::DragAcceptFiles(Handle, TRUE);
}
void __fastcall TForm1::DestroyWnd()
{
if( HandleAllocated() )
::DragAcceptFiles(Handle, FALSE);
TForm::DestroyWnd();
}
| Quote: | The problem is that the files are not accepted.
|
What all do you have on your form? Is any any empty areas? Calling
DragAcceptFiles() on the form's Handle means that only the form itself, not
its child controls, can accept dragged files. That means dragging the files
onto an empty area of the form itself. If you drag files onto the child
controls, they won't accept the files, unless you call DragAcceptFiles() for
them as well.
| Quote: | apart from that there is the following:
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Ignore that.
Gambit
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Remy Lebeau (TeamB)
Guest
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| Posted: Wed Mar 23, 2005 7:34 am Post subject: Re: Files Dragged into form??? |
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"qyte" <gyte (AT) vivodinet (DOT) gr> wrote
| Quote: | Could You be more specific? i have no idea of how to
implement what you say.
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I suggest you search online at http://www.deja.com and
http://www.google.com. This topic is discussed in detail in many places.
Gambit
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qyte
Guest
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| Posted: Wed Mar 23, 2005 7:46 am Post subject: Re: Files Dragged into form??? |
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Remy Lebeau (TeamB) wrote:
| Quote: | "qyte" <gyte (AT) vivodinet (DOT) gr> wrote in message
news:42411068$1 (AT) newsgroups (DOT) borland.com...
i did that and also call DragAcceptFiles(Form1->Handle,true)
in the constructor of the form.
If you call it in the constructor, then don't use the form's global pointer
as it hasn't been assigned yet. Use the implicit 'this' pointer instead,
ie:
DragAcceptFiles(this->Handle, TRUE)
A better place to call it is to override the CreateWnd() and DestroyWnd()
methods, ie:
void __fastcall TForm1::CreateWnd()
{
TForm::CreateWnd();
if( HandleAllocated() )
::DragAcceptFiles(Handle, TRUE);
}
void __fastcall TForm1::DestroyWnd()
{
if( HandleAllocated() )
::DragAcceptFiles(Handle, FALSE);
TForm::DestroyWnd();
}
The problem is that the files are not accepted.
What all do you have on your form? Is any any empty areas? Calling
DragAcceptFiles() on the form's Handle means that only the form itself, not
its child controls, can accept dragged files. That means dragging the files
onto an empty area of the form itself. If you drag files onto the child
controls, they won't accept the files, unless you call DragAcceptFiles() for
them as well.
apart from that there is the following:
Ignore that.
Gambit
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thanks a lot. it worked just fine. i used the two functions that you
recommended. i didn't try to use the constructor and destructor of the form.
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Michel Corbin
Guest
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| Posted: Wed Mar 23, 2005 5:18 pm Post subject: Re: Files Dragged into form??? |
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qyte wrote:
| Quote: |
i did that and also call DragAcceptFiles(Form1->Handle,true) in the
constructor of the form. The problem is that the files are not accepted.
apart from that there is the following:
[C++ Warning] files.h(239): W8027 Functions containing switch are not
expanded inline
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Sorry, as Gambit points it, I forgot to say :
In my programs I put
DragAcceptFiles(Handle,true) ;
in the constructor of the form.
You don't need to use this.
Michel
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