how to display progress bar in delphi? [duplicate] - delphi

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Closed 10 years ago.
Possible Duplicate:
how to display progress bar?
I created a steganalisys application and I want to add a progress bar to show how long the process works.
procedure TForm2.Button2Click(Sender: TObject);
var
q,x,y,leastSigBit,currentPixel,newPixelValue: integer;
pixels: PByteArray;
bmp: TBitmap;
begin
memo1.lines.clear;
Image2.Picture.Assign(Image1.Picture.Bitmap);
bmp := Image2.Picture.Bitmap;
for y := 0 to bmp.Height-1 do
begin
pixels := bmp.ScanLine[y];
for x := 0 to bmp.Width-1 do
begin
currentPixel := pixels[x];
leastSigBit := getBit(currentPixel, 0);
newPixelValue:=setBit(newPixelValue ,7,leastSigBit);
newPixelValue:=setBit(newPixelValue ,6,leastSigBit);
newPixelValue:=setBit(newPixelValue ,5,leastSigBit);
newPixelValue:=setBit(newPixelValue ,4,leastSigBit);
newPixelValue:=setBit(newPixelValue ,3,leastSigBit);
newPixelValue:=setBit(newPixelValue ,2,leastSigBit);
newPixelValue:=setBit(newPixelValue ,1,leastSigBit);
newPixelValue:=setBit(newPixelValue ,0,leastSigBit);
end;
pixels[x] := newPixelValue;
memo1.lines.append('pixel ke ' + inttostr(x) + ',' + inttostr(y) + ' desimal ' + inttostr(currentPixel) + ' (biner ' + toBinary(currentPixel) + ') ' +
' desimal baru ' + inttostr(newPixelValue) + ' (biner ' + toBinary(newPixelValue) + ')');
end;
end;
memo1.lines.append('All done!');
Button4.Enabled:=True;
Button2.Enabled:=False;
Button1.Enabled:=False;
Button5.Enabled:=True;
end;
how do I make a progress bar for the process? and where I have to put the command progress bar?

Answer 1

The correct way to do things like this is to do the computations in a background thread. Otherwise your GUI will freeze, and you might have trouble adding a Abort button. So you have to learn how to use threads (e.g., TThread) to do this properly. And your code must then be thread-safe, and you should only communicate between the thread code and the GUI in safe ways, e.g. using messages. The main ideas are found in my previous answer.
Anyhow, if you want to do this for educational purpouses or for private needs, perhaps the issues mentioned above aren't that severe. And then you can do simply like this:
procedure TForm2.Button2Click(Sender: TObject);
var
...
begin
ProgressBar1.Min := 0;
ProgressBar1.Max := bmp.Height;
ProgressBar1.Position := 0;
ProgressBar1.Step := 1;
for y := 0 to bmp.Height-1 do
begin
for x := 0 to bmp.Width-1 do
begin
end;
ProgressBar1.StepIt;
ProgressBar1.Update;
end;
end;
To try this, create a new VCL project. Add a TProgressBar and a TButton. In the OnClick event of the button, add the following code:
procedure TForm1.Button1Click(Sender: TObject);
var
i, j: integer;
begin
ProgressBar1.Min := 0;
ProgressBar1.Max := 100;
ProgressBar1.Position := 0;
ProgressBar1.Step := 1;
for i := 0 to 99 do
begin
for j := 0 to 200 do
begin
sleep(1);
end;
ProgressBar1.StepIt;
ProgressBar1.Update;
end;
end;
Be sure to notice the paramount backside of this approach, however. The application freezes during the entire 'computation'. You might not even be able to move the application window, and you will certainly not be able to interact with its GUI. Windows might even report the program as having freezed, and offer you the option to terminate it and send a bug report... Finally, since the entire GUI is down, there is no chance of adding a 'Stop computation' button. The solution? The dirty one is to use ProcessMessages and other filthy tricks. The proper one is to put the computation in its own thread, as already mentioned.