Delphi

问题 I'm using Delphi XE2 (Update 3) and GR32. I am unable to use TBitmap32.LoadFromStream() to load the image data. It raises the following exception: Project MyApp.exe raised exception class EInvalidGraphic with message 'Bitmap image is not valid'. Code uses GR32, GifImg, PngImage, Vcl.Graphics; var pic: TBitmap32; bs: TBytesStream; begin bs := TBytesStream.Create(TClientDataSet(cds).FieldByName('filedata').AsBytes); try pic := TBitmap32.Create; try // bs.SaveToFile('c:\delme.png'); // pic

问题 I'm asking this question because it turns out that there's some difficulty in writing a screensaver app in Delphi that's capable of running from the Logon screen. See question: Windows 7 logon screensaver in Delphi I've narrowed down the problem (or at least one problem) to a particular Win API call CreateEvent . SyncEvent := CreateEvent(nil, True, False, ''); if SyncEvent = 0 then RaiseLastOSError; This code only fails if called from the Logon screen. And GetLastError returns that access is

问题 I'm asking this question because it turns out that there's some difficulty in writing a screensaver app in Delphi that's capable of running from the Logon screen. See question: Windows 7 logon screensaver in Delphi I've narrowed down the problem (or at least one problem) to a particular Win API call CreateEvent . SyncEvent := CreateEvent(nil, True, False, ''); if SyncEvent = 0 then RaiseLastOSError; This code only fails if called from the Logon screen. And GetLastError returns that access is

问题 There is a software product called AnyChart which is great for embedding Flashed based charts in web pages. AnyCharts can also export to PNG file format. Here is an example: <script type="text/javascript" language="javascript"> //<![CDATA[ var chart = new AnyChart('http://www.mysite.com/swf/AnyChart.swf'); chart.width = 600; chart.height = 300; chart.setXMLFile('http://www.mysite.com/anychart.xml'); chart.addEventListener("draw", function() { saveChartAsImage(chart); }); chart.write("content

问题 I have an image like bellow i want to make the image become like I already make the code, like this : var Tx,Ty, R,G,B,A, posX, posY : integer; begin posX :=-1; posY := -1; for Ty:= 0 to Image1.Height-1 do begin for Tx:= 0 to Image1.Width-1 do begin R:= GetRValue(image1.Canvas.Pixels[Tx, Ty]); G:= GetGValue(image1.Canvas.Pixels[Tx, Ty]); B:= GetBValue(image1.Canvas.Pixels[Tx, Ty]); A:= (R + G + B) Div 3; if (A > 50) then begin Image1.Canvas.Pixels[Tx,Ty] := rgb(255,255,255); end else begin

问题 I have the following code: var sl: THashedStringList; begin sl:= THashedStringList.Create; sl.Duplicates := dupIgnore; sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); ShowMessage(IntToSTr(sl.Count)); end; But when I see sl.Count , it gives me 7. What is the bug in this? 回答1: You need to set the Sorted property to TRUE in order to have the list ignore duplicates. The property is inherited from TStringList , and if you look

问题 I have the following code: var sl: THashedStringList; begin sl:= THashedStringList.Create; sl.Duplicates := dupIgnore; sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); sl.Add('12345'); ShowMessage(IntToSTr(sl.Count)); end; But when I see sl.Count , it gives me 7. What is the bug in this? 回答1: You need to set the Sorted property to TRUE in order to have the list ignore duplicates. The property is inherited from TStringList , and if you look

问题 I have just seen a bit of code (D5) where they used... aStr:=tblAcct.FieldByName('Name').Text; It seems to work fine but I have always used... aStr:=tblAcct.FieldByName('Name').AsString; I have used both when loading a TMemo and again there seems no difference. aMemo.Lines.Text:=tblAcct.FieldByName('History').Text; aMemo.Lines.Text:=tblAcct.FieldByName('History').AsString; Is there a reason why I should use one over the other? If so, which one? Actually for TMemo, I usually use... aMemo.Lines

问题 Why this code does not crash? T is nil. How it is possible to access Caption if T is nil ? procedure Crash; VAR T: TButton; begin T:= NIL; T.Caption:= ''; <---------- this works end; 回答1: The TButton control is a wrapper around the Win32 Button control. It uses the Windows messaging system to operate upon it. And the core method for doing so, TControl.Perform() , has a built in safeguard against sending messages if Self is nil : function TControl.Perform(Msg: Cardinal; WParam: WPARAM; LParam: