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我正在尝试编写继承自FMX TStyledControl的类。样式更新时,它会加载要缓存的样式资源对象。使用RTTI加载FireMonkey风格资源
我创建了项目组,包含自定义控件并测试了在Delphi帮助中描述的FMX HD项目。在安装包并将TsgSlideHost放置在测试表单上后,我运行测试应用程序。它工作的很好,但是当我关闭它并尝试重建RAD Studio时,会出现“Error in rtl160.bpl”或“无效指针操作”。
从TsgStyledControl的LoadToCacheIfNeeded过程似乎是什么问题,但我不明白为什么。使用FMTI风格或其他任何方式的RTTI有没有限制?
TsgStyledControl来源:
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.
使用TsgStyledControl的:
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;
问题可能是因为在将其分配给Val之前,您没有验证StyleObj是否已分配?如果不是这样,我建议在运行时而不是设计时进行测试,以便您可以使用调试器或获取在设计时捕获错误的工具。 –
如果StyleObj为零,那么缓存字段也将为零。 TsgSlideHost检查这个。我试图在运行时调试它,它运行良好。 CodeSite记录器说明加载了3个字段,StyleObj类型是具有正确属性的TLayout。 AQTime分析器也不会检测到任何内存泄漏。 – HeMet