在早先的进度条控件版本中，例如在 Microsoft Windows Common Controls ActiveX 控件中提供的版本，您可以看到进度条有两种不同的视图。您可以通过设定 Scrolling 属性来设定 Standard 视图或是 Smooth 视图。 Smooth 视图提供了一个区域来平滑的显示进度， Standard 试图则看上去是由一个一个方块来表示进度的。
2、此时，您已经从 control 类继承了一个新类，并可以添加新的功能。但是，ProgressBar累是密封(sealed)的，不能再被继承。因此，您必须从头开始建立这个控件。
将下面的代码添加到UserControl模块中，就在“Windows Form Designer generated code”之后：
int min = 0; // Minimum value for progress range int max = 100; // Maximum value for progress range int val = 0; // Current progress Color BarColor = Color.Blue; // Color of progress meter
protected override void OnResize(EventArgs e) { // Invalidate the control to get a repaint. this.Invalidate(); }
protected override void OnPaint(PaintEventArgs e) { Graphics g = e.Graphics; SolidBrush brush = new SolidBrush(BarColor); float percent = (float)(val - min) / (float)(max - min); Rectangle rect = this.ClientRectangle;
// Calculate area for drawing the progress. rect.Width = (int)((float)rect.Width * percent);
// Draw the progress meter. g.FillRectangle(brush, rect);
// Draw a three-dimensional border around the control. Draw3DBorder(g);
// Clean up. brush.Dispose(); g.Dispose(); }
public int Minimum { get { return min; }
set { // Prevent a negative value. if (value < 0) { min = 0; }
// Make sure that the minimum value is never set higher than the maximum value. if (value > max) { min = value; min = value; }
// Ensure value is still in range if (val < min) { val = min; }
// Invalidate the control to get a repaint. this.Invalidate(); } }
public int Maximum { get { return max; }
set { // Make sure that the maximum value is never set lower than the minimum value. if (value < min) { min = value; }
max = value;
// Make sure that value is still in range. if (val > max) { val = max; }
// Invalidate the control to get a repaint. this.Invalidate(); } }
public int Value { get { return val; }
set { int oldValue = val;
// Make sure that the value does not stray outside the valid range. if (value < min) { val = min; } else if (value > max) { val = max; } else { val = value; }
// Invalidate only the changed area. float percent;
// Use a new value to calculate the rectangle for progress. percent = (float)(val - min) / (float)(max - min); newValueRect.Width = (int)((float)newValueRect.Width * percent);
// Use an old value to calculate the rectangle for progress. percent = (float)(oldValue - min) / (float)(max - min); oldValueRect.Width = (int)((float)oldValueRect.Width * percent);
Rectangle updateRect = new Rectangle();
// Find only the part of the screen that must be updated. if (newValueRect.Width > oldValueRect.Width) { updateRect.X = oldValueRect.Size.Width; updateRect.Width = newValueRect.Width - oldValueRect.Width; } else { updateRect.X = newValueRect.Size.Width; updateRect.Width = oldValueRect.Width - newValueRect.Width; }
updateRect.Height = this.Height;
// Invalidate the intersection region only. this.Invalidate(updateRect); } }
public Color ProgressBarColor { get { return BarColor; }
set { BarColor = value;
// Invalidate the control to get a repaint. this.Invalidate(); } }
private void Draw3DBorder(Graphics g) { int PenWidth = (int)Pens.White.Width;
g.DrawLine(Pens.DarkGray, new Point(this.ClientRectangle.Left, this.ClientRectangle.Top), new Point(this.ClientRectangle.Width - PenWidth, this.ClientRectangle.Top)); g.DrawLine(Pens.DarkGray, new Point(this.ClientRectangle.Left, this.ClientRectangle.Top), new Point(this.ClientRectangle.Left, this.ClientRectangle.Height - PenWidth)); g.DrawLine(Pens.White, new Point(this.ClientRectangle.Left, this.ClientRectangle.Height - PenWidth), new Point(this.ClientRectangle.Width - PenWidth, this.ClientRectangle.Height - PenWidth)); g.DrawLine(Pens.White, new Point(this.ClientRectangle.Width - PenWidth, this.ClientRectangle.Top), new Point(this.ClientRectangle.Width - PenWidth, this.ClientRectangle.Height - PenWidth)); }
