问题
I need to draw a checkbox in a particular column in aTListView, so i check this question How can I setup TListView with CheckBoxes in only certain columns? and in the accepted answer suggest use the method described in this another question How to set a Checkbox TStringGrid in Delphi?, now porting that code to work with a ListView i come with this :
procedure TForm15.ListView1CustomDrawSubItem(Sender: TCustomListView; Item: TListItem; SubItem: Integer; State: TCustomDrawState; var DefaultDraw: Boolean);
const
PADDING = 4;
var
h : HTHEME;
s : TSize;
r : TRect;
Rect : TRect;
i : Integer;
Dx : Integer;
begin
if (SubItem=1) then
begin
DefaultDraw:=True;
Rect :=Item.DisplayRect(drBounds);
Dx:=0;
for i := 0 to SubItem do
Inc(Dx,Sender.Column[i].Width);
Rect.Left :=Rect.Left+Dx;
Rect.Right :=Rect.Left+Sender.Column[SubItem+1].Width;
FillRect(Sender.Canvas.Handle, Rect, GetStockObject(WHITE_BRUSH));
s.cx := GetSystemMetrics(SM_CXMENUCHECK);
s.cy := GetSystemMetrics(SM_CYMENUCHECK);
if UseThemes then
begin
h := OpenThemeData(Sender.Handle, 'BUTTON');
if h <> 0 then
try
GetThemePartSize(h, Sender.Canvas.Handle, BP_CHECKBOX, CBS_CHECKEDNORMAL, nil, TS_DRAW, s);
r.Top := Rect.Top + (Rect.Bottom - Rect.Top - s.cy) div 2;
r.Bottom := r.Top + s.cy;
r.Left := Rect.Left + PADDING;
r.Right := r.Left + s.cx;
DrawThemeBackground(h, Sender.Canvas.Handle, BP_CHECKBOX, IfThen(CompareText(Item.SubItems[1],'True')=0, CBS_CHECKEDNORMAL, CBS_UNCHECKEDNORMAL), r, nil);
finally
CloseThemeData(h);
end;
end
else
begin
r.Top := Rect.Top + (Rect.Bottom - Rect.Top - s.cy) div 2;
r.Bottom := r.Top + s.cy;
r.Left := Rect.Left + PADDING;
r.Right := r.Left + s.cx;
DrawFrameControl(Sender.Canvas.Handle, r, DFC_BUTTON, IfThen(CompareText(Item.SubItems[1],'True')=0, DFCS_CHECKED, DFCS_BUTTONCHECK));
end;
//r := Classes.Rect(r.Right + PADDING, Rect.Top, Rect.Right, Rect.Bottom);
// DrawText(Sender.Canvas.Handle, StringGrid1.Cells[ACol, ARow], length(StringGrid1.Cells[ACol, ARow]), r, DT_SINGLELINE or DT_VCENTER or DT_LEFT or DT_END_ELLIPSIS);
end
else
DefaultDraw:=False;
end;
but i fail miserably in my attempt to draw a checkbox :(, can someone point me in the right direction to draw the checkbox in the listview, (the code does not draw any checkbox in the listview).
The listview is in vsReport mode and had 3 columns, i want put the checkbox in the third column. please don't suggest which use a thrid party component, i want use the TlistView control.
UPDATE 1 : thanks to the sertac recomendattion setting the DefaultDraw value now the checkboxes are shown, but the another columns looks awfull.
UPDATE 2 , following the Andreas suggestions the listview now look better, but still shown the black box;
procedure TForm15.ListView1CustomDrawSubItem(Sender: TCustomListView; Item: TListItem; SubItem: Integer; State: TCustomDrawState; var DefaultDraw: Boolean);
var
h : HTHEME;
s : TSize;
r : TRect;
Rect : TRect;
i : Integer;
Dx : Integer;
begin
if (SubItem=2) then
begin
DefaultDraw:=False;
Rect :=Item.DisplayRect(drBounds);
Dx:=0;
for i := 0 to SubItem-1 do
Inc(Dx,Sender.Column[i].Width);
Rect.Left :=Rect.Left+Dx;
Rect.Right :=Rect.Left+Sender.Column[SubItem].Width;
FillRect(Sender.Canvas.Handle, Rect, GetStockObject(WHITE_BRUSH));
s.cx := GetSystemMetrics(SM_CXMENUCHECK);
s.cy := GetSystemMetrics(SM_CYMENUCHECK);
Dx := (Sender.Column[SubItem].Width-GetSystemMetrics(SM_CXMENUCHECK)) div 2;
if UseThemes then
begin
h := OpenThemeData(Sender.Handle, 'BUTTON');
if h <> 0 then
try
GetThemePartSize(h, Sender.Canvas.Handle, BP_CHECKBOX, CBS_CHECKEDNORMAL, nil, TS_DRAW, s);
r.Top := Rect.Top + (Rect.Bottom - Rect.Top - s.cy) div 2;
r.Bottom := r.Top + s.cy;
r.Left := Rect.Left + Dx;
r.Right := r.Left + s.cx;
DrawThemeBackground(h, Sender.Canvas.Handle, BP_CHECKBOX, IfThen(CompareText(Item.SubItems[SubItem-1],'True')=0, CBS_CHECKEDNORMAL, CBS_UNCHECKEDNORMAL), r, nil);
finally
CloseThemeData(h);
end;
end
else
begin
r.Top := Rect.Top + (Rect.Bottom - Rect.Top - s.cy) div 2;
r.Bottom := r.Top + s.cy;
r.Left := Rect.Left + Dx;
r.Right := r.Left + s.cx;
DrawFrameControl(Sender.Canvas.Handle, r, DFC_BUTTON, IfThen(CompareText(Item.SubItems[SubItem-1],'True')=0, DFCS_CHECKED, DFCS_BUTTONCHECK));
end;
end;
end;
回答1:
One relatively simple way to get rid of this bug is to owner-draw the entire item. Set OwnerDraw := true, remove your OnCustomDrawSubItem routine, and add
procedure TForm15.ListView1DrawItem(Sender: TCustomListView; Item: TListItem;
Rect: TRect; State: TOwnerDrawState);
function ShrinkRect(const r: TRect; const X0, X1, Y0, Y1: integer): TRect; inline;
begin
result := r;
inc(result.Left, X0);
inc(result.Top, Y0);
dec(result.Right, X1);
dec(result.Bottom, Y1);
end;
const
CHECK_COL = 2;
PADDING = 4;
var
r: TRect;
i: Integer;
s: string;
size: TSize;
h: HTHEME;
begin
FillRect(Sender.Canvas.Handle, Rect, GetStockObject(WHITE_BRUSH));
r := Rect;
inc(r.Left, PADDING);
for i := 0 to TListView(Sender).Columns.Count - 1 do
begin
r.Right := r.Left + Sender.Column[i].Width;
if i <> CHECK_COL then
begin
if i = 0 then
begin
s := Item.Caption;
if not IsWindowVisible(ListView_GetEditControl(Sender.Handle)) then
begin
if UseThemes and ([odSelected, odHotLight] * State <> []) then
begin
h := OpenThemeData(Sender.Handle, 'LISTVIEW');
if h <> 0 then
try
DrawThemeBackground(h, Sender.Canvas.Handle, LVP_GROUPHEADER, IfThen(odSelected in State, LVGH_CLOSESELECTED, LVGH_OPENHOT), ShrinkRect(r, -2, 6, 1, 1), nil);
finally
CloseThemeData(h);
end;
end;
if (odSelected in State) and not UseThemes then
DrawFocusRect(Sender.Canvas.Handle, ShrinkRect(r, -2, 6, 1, 1));
end;
end
else
s := Item.SubItems[i - 1];
Sender.Canvas.Brush.Style := bsClear;
DrawText(Sender.Canvas.Handle,
PChar(s),
length(s),
r,
DT_SINGLELINE or DT_VCENTER or DT_LEFT or DT_END_ELLIPSIS);
end
else
begin
size.cx := GetSystemMetrics(SM_CXMENUCHECK);
size.cy := GetSystemMetrics(SM_CYMENUCHECK);
if UseThemes then
begin
h := OpenThemeData(Sender.Handle, 'BUTTON');
if h <> 0 then
try
GetThemePartSize(h, Sender.Canvas.Handle, BP_CHECKBOX, CBS_CHECKEDNORMAL, nil, TS_DRAW, size);
r.Top := Rect.Top + (Rect.Bottom - Rect.Top - size.cy) div 2;
r.Bottom := r.Top + size.cy;
r.Left := r.Left + PADDING;
r.Right := r.Left + size.cx;
DrawThemeBackground(h, Sender.Canvas.Handle, BP_CHECKBOX, IfThen(CompareText(Item.SubItems[1],'True')=0, CBS_CHECKEDNORMAL, CBS_UNCHECKEDNORMAL), r, nil);
finally
CloseThemeData(h);
end;
end
else
begin
r.Top := Rect.Top + (Rect.Bottom - Rect.Top - size.cy) div 2;
r.Bottom := r.Top + size.cy;
r.Left := r.Left + PADDING;
r.Right := r.Left + size.cx;
DrawFrameControl(Sender.Canvas.Handle, r, DFC_BUTTON, IfThen(CompareText(Item.SubItems[1],'True')=0, DFCS_CHECKED, DFCS_BUTTONCHECK));
end;
end;
inc(r.Left, Sender.Column[i].Width);
end;
end;
The code above needs further testing, but is probably in the right direction. Now it's very late, and I have to go.
回答2:
First, you should set DefaultDraw to false when drawing the checkbox column and true otherwise, because DefaultDraw means that the VCL does the drawing, and not you. Currently you do the opposite.
In addition, for some strange reason, the control considers the first sub item to be SubItem = 1, and the second sub item to SubItem = 2. Therefore, you should test if SubItem = 2 then instead.
[Of course, this implies the changes
for i := 0 to SubItem - 1 do
Inc(Dx, Sender.Column[i].Width);
Rect.Right := Rect.Left+Sender.Column[SubItem].Width;
]
The black rectangles appear to be a bug somewhere in the union of the VCL and Win32 code.
回答3:
Without completely switching over to OwnerDraw, I found the following reasonably acceptable:
- Don't populate the caption column (or use it for indexing) and set its initial width to 0
- Put your labels in the first SubItem column (2nd column) and then the checkboxes
Use the CustomDrawSubItem routine to draw your labels using "TextOut", for example:
ListView1.Canvas.TextOut(2, y, 'My label');
This hides the black boxes and you can see your text labels. However the selection does not work over the text. Small price to pay though, in my opinion.
来源：https://stackoverflow.com/questions/5519742/drawing-a-checkbox-in-a-tlistview