我试图在Win 7缩放轨道栏中复制PAINT应用程序的行为：
(我知道这是一个常见的跟踪栏控件)
(我知道这是一个常见的跟踪栏控件)
100％位于中心.
它有11个可用职位：
等等…
12.5％,25％,50％,100％,200％,300％,400％,500％,600％,700％,800％
所以我的缩放值(ZoomArray)是：
0.125,0.25,0.5,1,2,3,4,5,6,7,8
这很容易,我可以将最小值设置为1,最大值为11,并获取我需要的值：
ZoomArray [TrackBar1.Position]
问题是如何保持100％在中心,唯一可用的位置是上面的？
我试图在数组中使用虚拟值将1保留在中心,例如：
0.125,1 -1,-1,8
并且在“变更”事件中重新定位轨迹栏,但是我的逻辑似乎没有正确的工作.
有任何想法吗？
解决方法
这是从TTrackbar中导出新控件的一个替代方法,去除滚动消息中的自动提示和处理滑动,其行为与Paint中的控件几乎相同.用D2007编译,试图点评一下：
unit Unit1;
interface
uses
Windows,Messages,SysUtils,Classes,Controls,Forms,ComCtrls,StdCtrls;
type
TCNHScroll = TWMHScroll;
TTrackBar = class(comctrls.TTrackBar) // interposer class for quick test
protected
procedure CreateParams(var Params: TCreateParams); override;
procedure CreateWnd; override;
procedure CNHScroll(var Message: TCNHScroll); message CN_HSCROLL;
public
constructor Create(AOwner: TComponent); override;
end;
TForm1 = class(TForm)
Label1: TLabel;
TrackBar1: TTrackBar;
procedure TrackBar1Change(Sender: TObject);
end;
var
Form1: TForm1;
implementation
uses
commctrl;
{$R *.dfm}
procedure TForm1.TrackBar1Change(Sender: TObject);
begin
// account for non-linear scaling for a sensible value
if TrackBar1.Position <= 8 then
Label1.Caption := IntToStr(TrackBar1.Position * 125)
else
Label1.Caption := IntToStr(TrackBar1.Position * 1000 - 7000)
end;
{ TTrackBar }
constructor TTrackBar.Create(AOwner: TComponent);
begin
inherited;
// We'll have 15 positions which should account for the following values
// 125 250 - 500 - - - 1000 2000 3000 4000 5000 6000 7000 8000
// positions 3,5..7 will be skipped when tracking
Min := 1;
Max := 15;
LineSize := 1;
PageSize := 1;
end;
procedure TTrackBar.CreateParams(var Params: TCreateParams);
begin
inherited;
// remove automatic ticks so that we don't have ticks at 3 and 5..7
Params.Style := Params.Style and not TBS_AUTOTICKS;
end;
procedure TTrackBar.CreateWnd;
begin
inherited;
// first and last tick not required
SetTick(2); // 250
SetTick(4); // 500
SetTick(8); // 1000
SetTick(9); // 2000
SetTick(10);
SetTick(11);
SetTick(12);
SetTick(13);
SetTick(14); // 7000
end;
procedure TTrackBar.CNHscroll(var Message: TCNHScroll);
var
Pos: Integer;
begin
// prevent jumping back and forth while thumb tracking,do not slide to the
// next tick until a threshold is passed
if Message.ScrollCode = SB_THUMBTRACK then begin
case Message.Pos of
5: SendMessage(Handle,TBM_SETPOS,4);
6,7: SendMessage(Handle,8);
end;
end;
// for line and page and rest of the scrolling,skip certain ticks
Pos := SendMessage(Handle,TBM_GETPOS,0);
if Pos > Position then // compare with prevIoUs position
case Pos of
3: SendMessage(Handle,4);
5..7: SendMessage(Handle,8);
end;
if Pos < Position then
case Pos of
3: SendMessage(Handle,2);
5..7: SendMessage(Handle,4);
end;
inherited;
end;
end.
如果需要,垂直实施将是相似的.这不是一个完整的产品,只是一个模仿上述控件的行为的审判.