我該如何解決TScrollBar MouseWheel故障？

Question

我有一個TScrollBox在TFrame裏面，當我使用鼠標滾輪時，它不會向上或向下滾動滾動。

我曾嘗試使用

TScrollBox(Sender).Perform(WM_VSCROLL,1,0); 

在 FrameMouseWheelDown

，但它不會觸發。

任何想法？

Answer 1

我的滾動框看起來是這樣的：

type 
    TMyScrollBox = class(TScrollBox) 
    protected 
    function DoMouseWheel(Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint): Boolean; override; 
    procedure WndProc(var Message: TMessage); override; 
    end; 

function TMyScrollBox.DoMouseWheel(Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint): Boolean; 
begin 
    Result := inherited DoMouseWheel(Shift, WheelDelta, MousePos); 
    if not Result then begin 
    if Shift*[ssShift..ssCtrl]=[] then begin 
     VertScrollBar.Position := VertScrollBar.Position - WheelDelta; 
     Result := True; 
    end; 
    end; 
end; 

procedure TMyScrollBox.WndProc(var Message: TMessage); 
begin 
    if Message.Msg=WM_MOUSEHWHEEL then begin 
    (* For some reason using a message handler for WM_MOUSEHWHEEL doesn't work. The messages 
     don't always arrive. It seems to occur when both scroll bars are active. Strangely, 
     if we handle the message here, then the messages all get through. Go figure! *) 
    if TWMMouseWheel(Message).Keys=0 then begin 
     HorzScrollBar.Position := HorzScrollBar.Position + TWMMouseWheel(Message).WheelDelta; 
     Message.Result := 0; 
    end else begin 
     Message.Result := 1; 
    end; 
    end else begin 
    inherited; 
    end; 
end; 

Answer 2

可以使用OnMouseWheel事件處理程序：

ScrollBar1.OnMouseWheel := ScrollBoxMouseWheel; 
... 
procedure TFrame1.ScrollBoxMouseWheel(Sender: TObject; Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean); 
begin 
    Handled := True; 
    if WheelDelta < 0 then 
    TScrollBox(Sender).VertScrollBar.Position := TScrollBox(Sender).VertScrollBar.Position + TScrollBox(Sender).VertScrollBar.Increment 
    else 
    TScrollBox(Sender).VertScrollBar.Position := TScrollBox(Sender).VertScrollBar.Position - TScrollBox(Sender).VertScrollBar.Increment; 
end;