Most applications provide an area in the application's main form, usually aligned at the bottom of a form, used to display information about the application as it runs.
A TStatusBar component (located on the "Win32" page of the component palette) can be used to add a status bar to a form. A TStatusBar's Panels property is used to add, remove or modify the panels of the status bar (each panel is represented by a TStatusPanel object).
A TProgressBar (located on the "Win32" page of the component palette) displays a simple progress bar. Progress bars provide users with visual feedback about the progress of a procedure within an application.
PROGRESSBAR IN STATUSBAR
When placed on a form the TStatusBar automatically aligns itself to the bottom (Alignproperty = alBottom). Initially it has just one panel.
Here's how to add panels to the Panels collection (once a status bar has been added to a form, let's say it has the default "StatusBar1" name):
- Double click the status bar component to open the Panels editor
- Right click on the panel editor and select "Add" – this ads one TStatusPanel object to the Panels collection. Add one more.
- Select the first Panel, and using the Object Inspector, assign "Progress:" for theText property.
- Note: we are to place a progress bar into the second panel!
- Close the Panels editor
To display a progress bar inside one of the Progress bar Panel's, we first need a TProgressBar.
Drop one on the form, leave the default name (ProgressBar1).
Here's what needs to be done for ProgressBar to be displayed inside a StatusBar:
- Assign StatusBar1 for the Parent property of the ProgressBar1. Hint: "Parent vs. Owner"
- Change the Style property of the second StatusBar's panel to "psOwnerDraw". Hint: "Owner drawing in Delphi" When set to psOwnerDraw, the content displayed in the status panel is drawn at runtime on the status bar’s canvas by code in anOnDrawPanel event handler. Opposite to "psOwnerDraw", the default value of "psText", ensures the string contained in the Text property is displayed in the status panel, using the alignment specified by Alignment property.
- Handle the OnDrawPanel event of the StatusBar by adding the code that aligns the progress bar into a Panel of a status bar.
Here's the full code:
The first two steps in the above discussion are done in the Form's OnCreate event handler.
procedure TForm1.FormCreate(Sender: TObject); var ProgressBarStyle: integer; begin //enable status bar 2nd Panel custom drawing StatusBar1.Panels.Style := psOwnerDraw; //place the progress bar into the status bar ProgressBar1.Parent := StatusBar1; //remove progress bar border ProgressBarStyle := GetWindowLong(ProgressBar1.Handle, GWL_EXSTYLE); ProgressBarStyle := ProgressBarStyle - WS_EX_STATICEDGE; SetWindowLong(ProgressBar1.Handle, GWL_EXSTYLE, ProgressBarStyle); end;
Note: the TProgressBar control has a default border that would look "ugly" when the component is placed in the status bar – so we decide to remove the border.
Finally, handle the OnDrawPanel event of the StatusBar1:
procedure TForm1.StatusBar1DrawPanel( StatusBar: TStatusBar; Panel: TStatusPanel; const Rect: TRect); begin if Panel = StatusBar.Panels then with ProgressBar1 do begin Top := Rect.Top; Left := Rect.Left; Width := Rect.Right - Rect.Left - 15; Height := Rect.Bottom - Rect.Top; end; end;
All set. Run the project … with some dummy code in the OnClick event handler of a Button:
procedure TForm1.Button1Click(Sender: TObject); var i : integer; begin ProgressBar1.Position := 0; ProgressBar1.Max := 100; for i := 0 to 100 do begin ProgressBar1.Position := i; Sleep(25); //Application.ProcessMessages; end; end;
Progress bar in a ListView?
Here's how to add a progress bar to a ListView control. Plus: full source code to the TListViewEx component (TListView descendant) with ColumnResize events!
Progress bar in a message box?
Let's say you have a standard Windows dialog box displaying a question to the user with "Yes" and "No" buttons. Wouldn't it be great if a progress bar could be displayed within a dialog box "counting" seconds until the dialog box automatically closes itself?