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Windows Controls: The Track Bar

 
 

Introduction

A track bar is a control used to slide a small bar or pointer, also called a thumb, along a continuous line. In the following dialog box, there is an example of a track bar under Adjust the slider...:

The Editor Properties of Borland C++ Builder

To use the track bar, the user can drag the thumb in one of two directions. This changes the position of the thumb. The user can also click a position along the control line to place the thumb at a desired location. Alternatively, when the track bar has focus, the user can use the arrow keys to move the thumb.

As far as appearances are concerned, there are two types of track bars, depending on the orientation: horizontal or vertical. Here is an example of a vertical track bar on the left side of Medium:

Vertical Track Bar

A track bar is configured with a set of values from a minimum to a maximum. Therefore, the user can make a selection included in that range. Optionally, a track bar can be equipped with small marks called ticks. These can visually guide the user for the available positions of the thumb.

A track bar can be used as a progress control to help the user monitor an activity. A track bar also allows the user to specify a value that conforms to a range. When equipped with small indicators, also called ticks, a track bar can be used to control exact values that the user can select in a range, preventing the user from setting just any value.

Creating a Track Bar

To support track bars, the .NET Framework provides the TrackBar class. At design time, to add a track bar to your application, from the Toolbox, you can click the TrackBar button TrackBar and click the form or a container. The TrackBar class is derived from the Control class. To programmatically create a track bar, declare a variable of type TrackBar, use the new operator to allocate memory for the variable, and add it to the Controls property of its parent. Here is an example of creating a track bar:

using System;
using System.Drawing;
using System.Windows.Forms;

public class Exercise : System.Windows.Forms.Form
{
    TrackBar tbrSlider;

    public Exercise()
    {
        InitializeComponent();
    }

    private void InitializeComponent()
    {
        tbrSlider = new TrackBar();

        Controls.Add(tbrSlider);
    }
}

public class Program
{
    static int Main()
    {
        System.Windows.Forms.Application.Run(new Exercise());
        return 0;
    }
}

This would produce:

The Track Bar

 

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