我有以下课程:
TPNGButton = class(TNeoGraphicControl)
private
FImageDown: TPNGObject;
fImageNormal: TPNGObject;
fImageOver: TPNGObject;
...
public
...
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
published
property ImageNormal: TPNGObject read fImageNormal write SetImageNormal;
property ImageDown: TPNGObject read FImageDown write SetImageDown;
property ImageOver: TPNGObject read FImageOver write SetImageOver;
...
end;
我正在使用下面的函数将objFrom的属性复制到objTo作为参数.
procedure CopyObject(ObjFrom, ObjTo: TObject);
var
PropInfos: PPropList;
PropInfo: PPropInfo;
Count, Loop: Integer;
OrdVal: Longint;
StrVal: String;
FloatVal: Extended;
MethodVal: TMethod;
begin
{ Iterate thru all published fields and properties of source }
{ copying them to target }
{ Find out how many properties we'll be considering }
Count := GetPropList(ObjFrom.ClassInfo, tkAny, nil);
{ Allocate memory to hold their RTTI data }
GetMem(PropInfos, Count * SizeOf(PPropInfo));
try
{ Get hold of the property list in our new buffer }
GetPropList(ObjFrom.ClassInfo, tkAny, PropInfos);
{ Loop through all the selected properties }
for Loop := 0 to Count - 1 do
begin
PropInfo := GetPropInfo(ObjTo.ClassType, PropInfos^[Loop]^.Name);
{ Check the general type of the property }
{ and read/write it in an appropriate way }
case PropInfos^[Loop]^.PropType^.Kind of
tkInteger, tkChar, tkEnumeration,
tkSet, tkClass{$ifdef Win32}, tkWChar{$endif}:
begin
OrdVal := GetOrdProp(ObjFrom, PropInfos^[Loop]);
if Assigned(PropInfo) and (Assigned(PropInfo^.SetProc)) then
SetOrdProp(ObjTo, PropInfo, OrdVal); //here happens the bug...
end;
tkFloat:
begin
FloatVal := GetFloatProp(ObjFrom, PropInfos^[Loop]);
if Assigned(PropInfo) and (Assigned(PropInfo^.SetProc)) then
SetFloatProp(ObjTo, PropInfo, FloatVal);
end;
{$ifndef DelphiLessThan3}
tkWString,
{$endif}
{$ifdef Win32}
tkLString,
{$endif}
tkString:
begin
{ Avoid copying 'Name' - components must have unique names }
if UpperCase(PropInfos^[Loop]^.Name) = 'NAME' then
Continue;
StrVal := GetStrProp(ObjFrom, PropInfos^[Loop]);
if Assigned(PropInfo) and (Assigned(PropInfo^.SetProc)) then
SetStrProp(ObjTo, PropInfo, StrVal);
end;
tkMethod:
begin
MethodVal := GetMethodProp(ObjFrom, PropInfos^[Loop]);
if Assigned(PropInfo) and (Assigned(PropInfo^.SetProc)) then
SetMethodProp(ObjTo, PropInfo, MethodVal);
end
end
end
finally
FreeMem(PropInfos, Count * SizeOf(PPropInfo));
end;
end;
但是,当在SetOrdProp中传递PNGObject属性时,Delphi返回以下异常:
我的问题是:
我怎么知道PNGObject在SetOrdProp之前是否有一个有效的头?或者以另一种方式解决这个问题……
其他评论
>使用Assign方法作为以下代码并注释CopyObject函数:
TControl(objCtrlZ.Referencia).Assign(Component);
// "Component" is objFrom and objCtrlZ.Referencia is objTo
// CopyObject(Component, objCtrlZ.Referencia);
Delphi捕获以下异常:
最佳答案 我解决了我的问题.
要验证TPNGObject是否具有有效标头,我使用此代码:
objTemp := GetObjectProp(ObjFrom,PropInfos^[Loop]);
if ((TPNGObject(objTemp).Chunks.Count <> 0) and (TPNGObject(objTemp).Chunks.Item[0] is TChunkIHDR)) then begin ... end;
第一行我得到属性TPNGObject并且一如既往地分配对象objTemp无法获得AV.
为了验证Header,我在Chunks中验证count是否为零,如果Item [0]是TChunkIHDR,则知道是否是有效的头.
谢谢!