Delphi

问题 I am trying to load a png image into a TImage with Delphi XE4. The png starts off in a stream: E.g. Stream := TMemoryStream.Create; try Stream.LoadFromFile('c:\file.png'); Stream.Position := 0; Image1.Picture.Graphic.LoadFromStream(Stream); finally Stream.Free; end; I get an AV when I run this code. Can anyone tell me what I'm doing wrong? Thanks. 回答1: The TImage.Picture.Graphic property is nil until you load a graphic into the Picture . What you are asking for can be achieved as follows:

问题 MY application has had a mode for years where the customer can 'disable access to the OS'. Obviously this feature goes against the grain (at least as far as Windows is concerned) but there are installations where my App is the only program that should ever be visibile to a machine operator amd in this case such a feature is useful. The technigue I used was built from several 'layers': Hide the taskbar and button. Disable task-switching. Disable my main form system icons. To disable the

问题 If you will look at the code of FreeAndNil procedure you will see: procedure FreeAndNil(var Obj); var Temp: TObject; begin Temp := TObject(Obj); Pointer(Obj) := nil; Temp.Free; end; What is the reason they assigning Nil to an object reference and only after this destroying it? Why not vice-versa? 回答1: I can think of two reasons for doing it this way round, neither of which seems at all compelling. Reason 1: to guarantee that the reference is set to nil in case an exception is raised The

问题 I have a this code: for i:=0 to Memo1.Lines.Count-1 do begin while WebBrowser1.Busy do Application.ProcessMessages; WebBrowser1.OleObject.Document.Links.item(cat[i]).click; subcatList; end; but WebBrowser1 run several times in spite of the expectations of the procedure. How do I start WebBrowser1 not in the background or what is the solution? 回答1: You need to implement 3 events of TWebBrowser, BeforeNavigate2, DocumentComplete and NavigateComplete2 TForm1 = class(TForm) private CurDispatch:

问题 Does anyone have experience with using the Winspool.EnumprinterData API in Delphi? I found a demo for C++: https://s-kita.hatenablog.com/entry/20120227/1330353801 I tried to covert it to Delphi as below: procedure TForm1.GetPrinterData; var hPrinter : THandle; pInfo: PPrinterInfo2; bytesNeeded: DWORD; dwRet : DWORD; dwIndex: DWORD; pValueName: PWideChar; pTagName: PWideChar; cbValueName: DWORD; pcbValueName : DWORD; pType: DWORD; pData: PByte; cbData: DWORD; pcbData: PDWORD; i : Integer;

问题 We have a large application that works fine in Delphi 2006. We've moved it to XE5 and are experiencing frequent sporadic Access Violations. We're using VCL forms and a number of DevExpress and other third party components. We're working in Windows 7 Professional with Delphi XE Enterprise, Version 19.0.14356.6604. We've looked on line, here and elsewhere, for postings about A/Vs after porting to XE5 but haven't found anything that seems relevant to our problem. Here's what we know about the A

问题 If you will look at the code of FreeAndNil procedure you will see: procedure FreeAndNil(var Obj); var Temp: TObject; begin Temp := TObject(Obj); Pointer(Obj) := nil; Temp.Free; end; What is the reason they assigning Nil to an object reference and only after this destroying it? Why not vice-versa? 回答1: I can think of two reasons for doing it this way round, neither of which seems at all compelling. Reason 1: to guarantee that the reference is set to nil in case an exception is raised The

问题 I have an application that uses statically-linked runtime packages as well as designtime packages that use them. For some reason the code in any unit finalization section is not being run at runtime (I can't tell when this started happening). finalization ShowMessage('Goodbye'); end. Shutting Delphi down shows the message, but not when my application shuts down. It gets weirder in that if I put a breakpoint on ShowMessage, it breaks there but does not execute the line. If there are multiple

问题 The goal is to achieve full usage of the available cores, in converting floats to strings in a single Delphi application. I think this problem applies to the general processing of string. Yet in my example I am specifically using the FloatToStr method. What I am doing (I've kept this very simple so there is little ambiguity around the implementation): Using Delphi XE6 Create thread objects which inherit from TThread, and start them. In the thread execute procedure it will convert a large

问题 I am trying to assign an image(Image1) a picture at Run-time. Since I can't set a property to load from resource. So I need to load at run time. I have the code procedure TForm1.FormCreate(Sender: TObject); var RS:Tresourcestream ; begin RS := TResourceStream.Create(HInstance,'Splashscreen_Background', RT_RCDATA); image1.Picture.Bitmap.LoadFromResourcename(HInstance,'splashscreen_background'); end; But it just loads the forms with a blank Image. aswell as: procedure TForm1.FormCreate(Sender: