5.8 KiB
Progress Bar Control
The progress bar is generally used to prompt the progress of a task for the
user, and is frequently used for tasks such as copying file, installing
software. Calling CreateWindow function with CTRL_PROGRESSBAR as the
control class name can create a progress bar. Figure 1 is the typical running
effect of a progress bar.
Figure 1 Progress bar control
Styles of Progress Bar
Progress bar has only the following two styles available:
PBS_NOTIFY:The progress bar control with this style can generate notification messages.。PBS_VERTICAL:Display the progress bar vertically, as shown in Figure 2.
Figure 2 Vertical progress bar control
The combination of styles commonly used by a progress bar controls is:
Messages of Progress Bar
Setting Range of Progress Bar
The range of a progress bar is 0 to 100 by default, and an application can set
its own progress bar range by calling PBM_SETRANGE message:
[Prompt] The range of a progress bar can be set to be a negative value.
Setting Step Value of Progress Bar
We can set the step value for a progress bar, and make the progress bar
stepping forward when each stage task is complete. The step value is 10 by
default, and can be changed by sending PBM_SETSTEP message, as shown in the
following:
The above message changes the step value of a progress bar to be 5.
[Prompt] The step value of a progress bar can be set to be a negative value.
You should set the position of the progress bar as the max value of its range when the step value is a negative and the progress bar will decrease from its max range to min.
Setting Position of Progress Bar
We can also set the current position of a progress bar optionally with
PBM_SETPOS message:
The above message sets the current position of a progress bar to be 50.
Setting Offset Based-on Current Position
We can also set the offset of the new position based on the current position to change the progress position:
The above message will add 10 to the new position based on the current position, i.e., new position is the current position plus 10.
[Prompt] The offset of a progress bar can be set to be a negative value.
Advancing Position by One Step
PBM_STEPIT can be sent to advance the current position, and the new position
equals the result of the current position plus the step value:
[Note] The present progress bar control does not provide any messages for getting the current position, the current step increment, and the current position range.
Notification Codes of Progress Bar
Progress bar with PBS_NOTIFY style may possibly generate the following
notification codes:
PBN_REACHMAX:Reach the maximum position.PBN_REACHMIN:Reach the minimum position.
Sample Program
List 1 gives an example of using the progress bar control. This program
provides two functions. Calling createProgressWin function will create a main
window with a progress bar and then return. We can control the progress bar of
the main window in our own program, and call destroyProgressWin function to
destroy the progress main window after completing the task. The two functions
actually come from MiniGUIExt library of MiniGUI. List 1 gives the example of
the implementation and the usage of these two functions, and the running effect
is as shown in Figure 3. Please refer to progressbar.c of the sample program
package mg-samples of this guide for the complete source code.
List 1 Example of using progress bar
Figure 3 Example of progress bar control
-- Main.XiaodongLi - 26 Oct 2009
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