C# WinForm控件美化扩展系列之ListView
昨天的文章中介绍了怎样使ListBox隔行显示不同的颜色，今天接着介绍怎样扩展ListView控件，使他也具有这样的功能，而且重绘他的Header，使其更美观。
在这篇文章中，我只对View 为 Details的时候进行了重绘，至于其他的Ttile，List，SmallIcon，LargeIcon，大家可以照着代码自己实现。
这个控件的美化大致跟ListBox的差不了多少，我们还是一步一步的来实现它吧：
1、 继承ListView，并把 OwnerDraw 设为True,如下：
public ListViewEx()
: base()
{
base.OwnerDraw = true;
}
2、 给继承的控件添加4个属性：RowBackColor1，RowBackColor2，SelectedColor，HeadColor这三个颜色分别是数据项的交替的背景色、数据项选择后的背景色和列表头的背景颜色。
3、 重绘Header，通过重写OnDrawColumnHeader函数来实现。
protected override void OnDrawColumnHeader(
DrawListViewColumnHeaderEventArgs e)
{
base.OnDrawColumnHeader(e);
Graphics g = e.Graphics;
Rectangle bounds = e.Bounds;
Color baseColor = _headColor;
Color borderColor = _headColor;
Color innerBorderColor = Color.FromArgb(200, 255, 255);
RenderBackgroundInternal(g,bounds,baseColor,borderColor,innerBorderColor,0.35f,true,LinearGradientMode.Vertical);
TextFormatFlags flags = GetFormatFlags(e.Header.TextAlign);
Rectangle textRect = new Rectangle(bounds.X + 3,bounds.Y,bounds.Width - 6,bounds.Height); ;
if (e.Header.ImageList != null)
{
Image image = e.Header.ImageIndex == -1 ? null : e.Header.ImageList.Images[e.Header.ImageIndex];
if (image != null)
{
Rectangle imageRect = new Rectangle(bounds.X + 3,bounds.Y + 2,bounds.Height - 4,bounds.Height - 4);
g.InterpolationMode = InterpolationMode.HighQualityBilinear;
g.DrawImage(image, imageRect);
textRect.X = imageRect.Right + 3;
textRect.Width -= imageRect.Width;
}
}
TextRenderer.DrawText( g, e.Header.Text, e.Font,textRect, e.ForeColor,flags);
}
4、 重绘 Item，通过重写OnDrawItem，OnDrawSubItem来实现，这里我只对Details这种显示模式进行了重写。
protected override void OnDrawItem(DrawListViewItemEventArgs e)
{
base.OnDrawItem(e);
if (View != View.Details)
{
e.DrawDefault = true;
}
}
protected override void OnDrawSubItem(DrawListViewSubItemEventArgs e)
{
base.OnDrawSubItem(e);
if (View != View.Details)
{
return;
}
if(e.ItemIndex == -1)
{
return;
}
Rectangle bounds = e.Bounds;
ListViewItemStates itemState = e.ItemState;
Graphics g = e.Graphics;
if ((itemState & ListViewItemStates.Selected) == ListViewItemStates.Selected)
{
bounds.Height--;
Color baseColor = _selectedColor;
Color borderColor = _selectedColor;
Color innerBorderColor = Color.FromArgb(200, 255, 255);
RenderBackgroundInternal(g,bounds,baseColor, borderColor,innerBorderColor, 0.35f,true,LinearGradientMode.Vertical);
bounds.Height++;
}
else
{
Color backColor = e.ItemIndex % 2 == 0 ?
_rowBackColor1 : _rowBackColor2;
using (SolidBrush brush = new SolidBrush(backColor))
{
g.FillRectangle(brush, bounds);
}
}
TextFormatFlags flags = GetFormatFlags(e.Header.TextAlign);
if (e.ColumnIndex == 0)
{
if (e.Item.ImageList == null)
{
e.DrawText(flags);
return;
}
Image image = e.Item.ImageIndex == -1 ?
null : e.Item.ImageList.Images[e.Item.ImageIndex];
if (image == null)
{
e.DrawText(flags);
return;
}
Rectangle imageRect = new Rectangle( bounds.X + 4, bounds.Y + 2, bounds.Height - 4,bounds.Height - 4);
g.DrawImage(image, imageRect);
Rectangle textRect = new Rectangle(imageRect.Right + 3, bounds.Y, bounds.Width - imageRect.Right - 3, bounds.Height);
TextRenderer.DrawText( g, e.Item.Text, e.Item.Font, textRect, e.Item.ForeColor, flags);
return;
}
e.DrawText(flags);
}
以上内容转载自：http://www.csharpwin.net/ddwstp/net/csharp/418dr7279.shtml
下面是自己的心得与补充
上文中调用的函数RenderBackgroundInternal具体代码如下：
public static void RenderBackgroundInternal(Graphics g, Rectangle rect,
Color baseColor, Color borderColor, Color innerBorderColor,
float basePosition, bool drawBorder, LinearGradientMode mode)
{
if (drawBorder)
{
rect.Width--;
rect.Height--;
}
using (LinearGradientBrush brush = new LinearGradientBrush(
rect, Color.Transparent, Color.Transparent, mode))
{
Color[] colors = new Color[4];
colors[0] = GetColor(baseColor, 0, 35, 24, 9);
colors[1] = GetColor(baseColor, 0, 13, 8, 3);
colors[2] = baseColor;
colors[3] = GetColor(baseColor, 0, 68, 69, 54);
ColorBlend blend = new ColorBlend();
blend.Positions = new float[] { 0.0f, basePosition, basePosition + 0.05f, 1.0f };
blend.Colors = colors;
brush.InterpolationColors = blend;
g.FillRectangle(brush, rect);
}
if (baseColor.A > 80)
{
Rectangle rectTop = rect;
if (mode == LinearGradientMode.Vertical)
{
rectTop.Height = (int)(rectTop.Height * basePosition);
}
else
{
rectTop.Width = (int)(rect.Width * basePosition);
}
using (SolidBrush brushAlpha =
new SolidBrush(Color.FromArgb(80, 255, 255, 255)))
{
g.FillRectangle(brushAlpha, rectTop);
}
}
if (drawBorder)
{
using (Pen pen = new Pen(borderColor))
{
g.DrawRectangle(pen, rect);
}
rect.Inflate(-1, -1);
using (Pen pen = new Pen(innerBorderColor))
{
g.DrawRectangle(pen, rect);
}
}
}
private static Color GetColor(Color colorBase, int a, int r, int g, int b)
{
int a0 = colorBase.A;
int r0 = colorBase.R;
int g0 = colorBase.G;
int b0 = colorBase.B;
if (a + a0 > 255) { a = 255; } else { a = Math.Max(a + a0, 0); }
if (r + r0 > 255) { r = 255; } else { r = Math.Max(r + r0, 0); }
if (g + g0 > 255) { g = 255; } else { g = Math.Max(g + g0, 0); }
if (b + b0 > 255) { b = 255; } else { b = Math.Max(b + b0, 0); }
return Color.FromArgb(a, r, g, b);
}
上文中,函数GetFormatFlags(e.Header.TextAlign);不知道到底是啥，自己改写成TextFormatFlags.xxx（XXX按照自己需求填写）；
