The ProgressBar component is used to indicate the process of executing a task.
To use the component, in the Min and Max properties define indicator scale minimum and maximum values. In the Position property set the current value displayed in the indicator. Various additional properties enable the user to set up component appearance.
When working in Windows 7 operating system using the Aero theme, smooth progress bar is used. If values change quite rapidly (in several seconds), progress bar lag occurs. Such a lag is not an error in the ProgressBar operation; it is an operating result of the system component behind ProgressBar. If the process initiated by the ProgressBar component is in progress for a short time period and timely progress bar display is required, the following bypass can be used: prior to setting in the Position property the value displayed by the progress bar, a slightly increased value should be set for such property. It causes an instant rendering of the progress bar. To improve progress bar display at the end point (when the Max value is reached), slightly increase maximum permissible component range, set progress bar value and reset initial maximum permissible value.
If progress bar value is changed according to timer control, to enable correct display using the above algorithm, use the following code in Fore language:
Class TESTForm: Form
Button1: Button;
Timer1: Timer;
ProgressBar1: ProgressBar;
Pos: Integer;
Sub Button1OnClick(Sender: Object; Args: IMouseEventArgs);
Begin
Pos := 0;
Timer1.Enabled := True;
End Sub Button1OnClick;
Sub Timer1OnTimer(Sender: Object; Args: IEventArgs);
Begin
Pos := Pos + 1;
If (Pos < ProgressBar1.Max) Then
ProgressBar1.Position := Pos + 1;
ProgressBar1.Position := Pos;
Else
ProgressBar1.Max := ProgressBar1.Max + 1;
ProgressBar1.Position := ProgressBar1.Max;
ProgressBar1.Max := ProgressBar1.Max - 1;
Timer1.Enabled := False;
End If;
End Sub Timer1OnTimer;
End Class TESTForm;
It is also recommended to consider using the PPProgressBar component instead of the ProgressBar component. PPProgressBar does not depend on system components, therefore display lag does not occur.
| Property name | Brief description | |
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Align | The Align property determines behavior of the component when its parent component is resized. |
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AllowDrag | The AllowDrag property determines whether an object can be dragged from the component. |
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AllowDrop | The AllowDrop property determines whether the component can accept a dragged object. |
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Anchors | The Anchors property returns settings that determine the percentage of the size change for the current component when the parent component is resized. |
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BorderStyle | The BorderStyle property determines a component border style. |
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Brush | The Brush property determines the brush that is used to fill component area. |
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ClientHeight | The ClientHeight property is used to receive or specify the height of the component’s client area. |
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ClientWidth | The ClientWidth property is used to receive or specify the width of the component’s client area. |
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Color | The Color property determines a component background color. |
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ComponentCount | The ComponentCount property returns the number of child components. |
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Components | The Components property returns the child component. |
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Cursor | The Cursor property determines the look of the cursor over the component. |
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Data | The Data property is used to store any custom data. |
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Enabled | The Enabled property determines whether the component is available for the user. |
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Focused | The Focused property returns True if the focus is set on the component. |
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Font | The Font property determines the set of characteristics describing the font that is used to display text. |
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Height | The Height property determines component height. |
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HelpContext | The HelpContext property determines a unique index for the context help section for this component. |
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Hint | The Hint property determines a component tooltip text. |
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Left | The Left property determines the coordinate of the left border of the component. |
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Max | The Max property determines the maximum value for the progress bar. |
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Min | The Min property determines the minimum value for the progress bar. |
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Name | The Name property determines a component name. |
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Orientation | The Orientation property determines the indicator orientation. |
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Parent | The Parent property determines a parent component. |
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ParentColor | The ParentColor property determines whether the component inherits the color of the parent component. |
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ParentFont | The ParentFont property determines whether the component uses the font of the parent component. |
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ParentShowHint | The ParentShowHint property determines whether a tooltip is displayed. |
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PopupMenu | The PopupMenu property determines the context menu opened by clicking the component with the additional mouse button. |
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Position | The Position property determines the current position of the indicator. |
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Scrolls | The Scrolls property returns parameters of component's scrollbars. |
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ShowHint | The ShowHint property enables and disables showing a component tooltip. |
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Smooth | The Smooth property determines the progress bar appearance. |
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StepSize | The StepSize property determines the value to move the progress bar on calling the StepIt method. |
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TabOrder | The TabOrder property determines the component position in the tab order. |
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TabStop | The TabStop property determines whether the component is focused when the TAB key is pressed. |
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Tag | The Tag property is not used by the compiler. The user can change the value of the Tag property and use it as he wishes. |
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Text | The Text property determines the row identifying a component for the user. |
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Top | The Top property determines the coordinate of the top border of the component. |
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Visible | The Visible property determines visibility of the component during execution. |
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Width | The Width property determines component width. |
| Method name | Brief description | |
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BringToFront | The BringToFront method brings a component to front. |
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ClientToScreen | The ClientToScreen method converts the coordinates of a point specified relative to the component coordinate system into screen coordinates. |
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DoDragDrop | The DoDragDrop method enables to start dragging operation. |
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GetImage | The GetImage method returns the image of the component with all the child components. |
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ScreenToClient | The ScreenToClient method converts screen coordinates of a point into coordinates specified relative to the component coordinate system. |
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SendToBack | The SendToBack method sends a component to back. |
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SetFocus | The SetFocus method sets focus to this component. |
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StepBy | The StepBy method changes the indicator position by the value, set in the input parameter. |
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StepIt | The StepIt method changes the indicator position by the value, set in the StepSize property. |
| Event name | Brief description | |
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OnBeginDrag | The OnBeginDrag event occurs for a component when the user starts to drag an object from the component. |
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OnClick | The OnClick event occurs if the user clicks the component area. |
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OnDblClick | The OnDblClick event occurs if the user double-clicks the component area. |
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OnDragDrop | The OnDragDrop event occurs for the component if the user drops a dragged object over it. |
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OnDragEnter | The OnDragEnter event occurs when a dragged object crosses the borders of this component. |
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OnDragLeave | The OnDragLeave event occurs when a dragged object leaves the borders of this component. |
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OnDragOver | The OnDragOver event occurs for the component when the user drags an object over it. |
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OnEnter | The OnEnter event occurs when the component receives focus. |
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OnExit | The OnExit event occurs when the component loses focus. |
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OnHScroll | The OnHScroll event occurs when horizontal scrollbar slider changes its position. |
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OnKeyDown | The OnKeyDown event occurs if the component is focused and a keyboard key is pressed. |
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OnKeyPress | The OnKeyPress event occurs if the component is focused when the user presses a character key. |
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OnKeyPreview | The OnKeyPreview event occurs prior to each event related to key pressing. |
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OnKeyUp | The OnKeyUp event occurs if the component is focused and the user releases any button previously pressed. |
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OnMouseDown | The OnMouseDown event occurs if the pointer is in component's area and a mouse key is pressed. |
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OnMouseEnter | The OnMouseEnter event occurs when mouse cursor enters the component area. |
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OnMouseHover | The OnMouseHover event occurs when mouse cursor is held in the component area. |
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OnMouseLeave | The OnMouseLeave event occurs when mouse cursor leaves the component area. |
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OnMouseMove | The OnMouseMove event occurs on moving the cursor over component. |
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OnMouseUp | The OnMouseUp event occurs on releasing mouse button when the cursor is in component area. |
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OnMouseWheel | The OnMouseWheel event occurs if the component is focused when the mouse wheel is rotated. |
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OnVScroll | The OnVScroll event occurs when vertical scrollbar slider changes its position. |
See also: