I am trying to write a class that inherits from FMX TStyledControl. When a style is updated, it loads style resource objects into the cache.
I created a project group for a user control pack and tested the FMX HD project as described in the Delphi help. After installing the package and placing TsgSlideHost in the test form, I launch the test application. It works well, but when I close it and try to rebuild the package, RAD Studio says "Error in rtl160.bpl" or "incorrect pointer operation".
It seems like a problem in the LoadToCacheIfNeeded procedure from TsgStyledControl, but I don't understand why. Are there any restrictions on using RTTI with FMX styles or something else?
Sources of TsgStyledControl:
unit SlideGUI.TsgStyledControl; interface uses System.SysUtils, System.Classes, System.Types, FMX.Types, FMX.Layouts, FMX.Objects, FMX.Effects, System.UITypes, FMX.Ani, System.Rtti, System.TypInfo; type TCachedAttribute = class(TCustomAttribute) private fStyleName: string; public constructor Create(const aStyleName: string); property StyleName: string read fStyleName; end; TsgStyledControl = class(TStyledControl) private procedure CacheStyleObjects; procedure LoadToCacheIfNeeded(aField: TRttiField); protected function FindStyleResourceAs<T: class>(const AStyleLookup: string): T; function GetStyleName: string; virtual; abstract; function GetStyleObject: TControl; override; public procedure ApplyStyle; override; published { Published declarations } end; implementation { TsgStyledControl } procedure TsgStyledControl.ApplyStyle; begin inherited; CacheStyleObjects; end; procedure TsgStyledControl.CacheStyleObjects; var ctx: TRttiContext; typ: TRttiType; fld: TRttiField; begin ctx := TRttiContext.Create; try typ := ctx.GetType(Self.ClassType); for fld in typ.GetFields do LoadFromCacheIfNeeded(fld); finally ctx.Free end; end; function TsgStyledControl.FindStyleResourceAs<T>(const AStyleLookup: string): T; var fmxObj: TFmxObject; begin fmxObj := FindStyleResource(AStyleLookup); if Assigned(fmxObj) and (fmxObj is T) then Result := fmxObj as T else Result := nil; end; function TsgStyledControl.GetStyleObject: TControl; var S: TResourceStream; begin if (FStyleLookup = '') then begin if FindRCData(HInstance, GetStyleName) then begin S := TResourceStream.Create(HInstance, GetStyleName, RT_RCDATA); try Result := TControl(CreateObjectFromStream(nil, S)); Exit; finally S.Free; end; end; end; Result := inherited GetStyleObject; end; procedure TsgStyledControl.LoadToCacheIfNeeded(aField: TRttiField); var attr: TCustomAttribute; styleName: string; styleObj: TFmxObject; val: TValue; begin for attr in aField.GetAttributes do begin if attr is TCachedAttribute then begin styleName := TCachedAttribute(attr).StyleName; if styleName <> '' then begin styleObj := FindStyleResource(styleName); val := TValue.From<TFmxObject>(styleObj); aField.SetValue(Self, val); end; end; end; end; { TCachedAttribute } constructor TCachedAttribute.Create(const aStyleName: string); begin fStyleName := aStyleName; end; end.
Using TsgStyledControl:
type TsgSlideHost = class(TsgStyledControl) private [TCached('SlideHost')] fSlideHost: TLayout; [TCached('SideMenu')] fSideMenuLyt: TLayout; [TCached('SlideContainer')] fSlideContainer: TLayout; fSideMenu: IsgSideMenu; procedure ReapplyProps; procedure SetSideMenu(const Value: IsgSideMenu); protected function GetStyleName: string; override; function GetStyleObject: TControl; override; procedure UpdateSideMenuLyt; public constructor Create(AOwner: TComponent); override; procedure ApplyStyle; override; published property SideMenu: IsgSideMenu read fSideMenu write SetSideMenu; end;
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