文件名称：选择一个选项后可以返回一个值的ComboBox
文件大小：3KB
文件格式：PAS
更新时间：2009-03-15 02:52:39
控件 源码 系统相关类 资源
用法举例：从数据表中name字段写入VALComboBox的items,id字段写入VALComboBox的values,当从VALComboBox选择一个选项后，就可以从value属性获得相应的ID值，或者写value的值为某ID值，VALComboBox将定位在相应的选项上；unit VALComboBox;interfaceuses SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls, Forms, Menus, Dialogs, StdCtrls;type TValComboBox = class(TComboBox) private FValue: PString; FValues: TStrings; FOnChange: TNotifyEvent; function GetValue: string; function GetButtonValue(Index: Integer): string; procedure SetValue(const Value: string); procedure SetValues(Value: TStrings); protected procedure Change; dynamic; procedure Notification(AComponent: TComponent; Operation: TOperation); override; public constructor Create(AOwner: TComponent); override; destructor Destroy; override; property Value: string read GetValue write SetValue; property ItemIndex; published property Values: TStrings read FValues write SetValues; property OnChange: TNotifyEvent read FOnChange write FOnChange; end;procedure Register;implementationconstructor TValComboBox.Create(AOwner: TComponent);begin inherited Create(AOwner); FValue := NullStr; FValues := TStringList.Create; style := csDropDownList;end;destructor TValComboBox.Destroy;begin DisposeStr (FValue); FValues.Free; inherited Destroy;end;procedure TValComboBox.Notification(AComponent: TComponent; Operation: TOperation);begin inherited Notification(AComponent, Operation);end;function TValComboBox.GetValue : string;begin result:=values[itemindex];end;function TValComboBox.GetButtonValue(Index: Integer): string;begin if (Index < FValues.Count) and (FValues[Index] <> ‘‘) then Result := FValues[Index] else if (Index < Items.Count) then Result := Items[Index] else Result := ‘‘;end;procedure TValComboBox.SetValue (const Value: string);var I : Integer;begin AssignStr(FValue, Value); if (ItemIndex < 0) or (GetButtonValue(ItemIndex) <> Value) then begin if (ItemIndex >= 0) then ItemIndex := -1; for I := 0 to Items.Count - 1 do begin if GetButtonValue(I) = Value then begin ItemIndex := I; break; end; end; Change; end;end;procedure TValComboBox.SetValues(Value: TStrings);begin FValues.Assign(Value);end;procedure TValComboBox.Change;begin if Assigned(FOnChange) then FOnChange(Self);end;procedure Register;begin RegisterComponents(‘mycomponent‘, [TValComboBox]);end;end.