[原創][開源] SunnyUI.Net 開發日志：UIListBox 增加跟隨滑鼠滑過高亮

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 SunnyUI.Net 開發日志：ListBox 增加跟隨滑鼠滑過高亮

 QQ群里，寸木說，ListBox滑鼠移動時，當前行需要焦點，我想了想，不難實作啊

不就是在滑鼠移動時重繪Item嘛，何況選中的Item已經改了顏色了，

見UIListBox代碼：

protected override void OnDrawItem(DrawItemEventArgs e)
        {
            base.OnDrawItem(e);
            BeforeDrawItem?.Invoke(this, Items, e);
            if (Items.Count == 0)
            {
                return;
            }

            e.DrawBackground();

            if (e.Index < 0 || e.Index >= Items.Count)
            {
                return;
            }

            StringFormat sStringFormat = new StringFormat();
            sStringFormat.LineAlignment = StringAlignment.Center;

            Color backColor = (e.State & DrawItemState.Selected) == DrawItemState.Selected ? ItemSelectBackColor : BackColor;
            Color foreColor = (e.State & DrawItemState.Selected) == DrawItemState.Selected ? ItemSelectForeColor : ForeColor;

            Rectangle rect = new Rectangle(e.Bounds.X, e.Bounds.Y, e.Bounds.Width - 1, e.Bounds.Height - 1);
            e.Graphics.FillRectangle(BackColor, e.Bounds);
            e.Graphics.FillRoundRectangle(backColor, rect, 5);
            e.Graphics.DrawString(Items[e.Index].ToString(), e.Font, foreColor, e.Bounds, sStringFormat);
        }

看：(e.State & DrawItemState.Selected) == DrawItemState.Selected 選中行狀態嘛

看了e.State有e.State == DrawItemState.HotLight，不就是高亮的么，于是開始擼代碼，加狀態判斷

Run

暈，，，沒變，這HotLight不起作用，好吧，問度娘，，，

翻山越嶺，跋山涉水，，，

找到這篇：https://www.jb51.cc/csharp/101121.html

其中提到：

   我在我的WinForms應用程式中使用OwnerDrawFixed作為DrawMode用于自定義ListBox控制元件.當用戶將滑鼠懸停在串列框專案上時,我希望重新繪制ListBoxItem的背景(或執行其他操作),即在MouseMove …DrawItemState.HotLight永遠不適用于ListBox,所以我想知道如何模擬它,如何解決這個問題.

DrawItemState.HotLight永遠不適用于ListBox，是永遠，，，怎么這么遠，，，

繼續往下看：

解決方法

DrawItemState.HotLight僅適用于所有者繪制的選單,而不適用于串列框.對于ListBox,您必須自己跟蹤專案：

public partial class Form1 : Form
{
  private int _MouseIndex = -1;
 
  public Form1()
  { InitializeComponent(); }
 
  private void listBox1_DrawItem(object sender,DrawItemEventArgs e)
  {
    Brush textBrush = SystemBrushes.WindowText;
 
    if (e.Index > -1)
    {
      if (e.Index == _MouseIndex)
      {
        e.Graphics.FillRectangle(SystemBrushes.HotTrack,e.Bounds);
        textBrush = SystemBrushes.HighlightText;
      }
      else
      {
        if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
        {
          e.Graphics.FillRectangle(SystemBrushes.Highlight,e.Bounds);
          textBrush = SystemBrushes.HighlightText;
        }
        else
          e.Graphics.FillRectangle(SystemBrushes.Window,e.Bounds);
      }
      e.Graphics.DrawString(listBox1.Items[e.Index].ToString(),e.Font,textBrush,e.Bounds.Left + 2,e.Bounds.Top);
    }
  }
 
  private void listBox1_MouseMove(object sender,MouseEventArgs e)
  {
    int index = listBox1.IndexFromPoint(e.Location);
    if (index != _MouseIndex)
    {
      _MouseIndex = index;
      listBox1.Invalidate();
    }
  }
 
  private void listBox1_MouseLeave(object sender,EventArgs e)
  {
    if (_MouseIndex > -1)
    {
      _MouseIndex = -1;
      listBox1.Invalidate();
    }
  }
}

兄弟們，人家這花兩年時間解決的，應該有用，繼續再找找，又找到一篇洋文的：

https://stackoverflow.com/questions/1316027/listbox-drawitem-hotlight-state-in-the-ownerdraw-mode

It took me only two years to find the answer for you, but here it is:

The DrawItemState.HotLight only applies to owner drawn menus, not the listbox.

For the ListBox, you have to keep track of the item yourself:

看看，也是兩年，估計上面中文的從這個翻譯過來，

除了這倆，還真沒找到，

繼續擼代碼，果真管用，不過還是有問題，滑鼠滑快了，ListBox閃爍的厲害，

分析代碼  listBox1.Invalidate(); 這是重繪全部的，滑鼠滑過也就和本次選中和上次選中的有關系，

就刷這兩個Item就行，有了思路，擼代碼三連發：

        private int lastIndex = -1;
        private int mouseIndex = -1;

        [Browsable(false)]
        public int MouseIndex
        {
            get => mouseIndex;
            set
            {
                if (mouseIndex != value)
                {
                    if (lastIndex >= 0 && lastIndex != SelectedIndex)
                    {
                        OnDrawItem(new DrawItemEventArgs(this.CreateGraphics(), Font, GetItemRectangle(lastIndex), lastIndex, DrawItemState.Grayed));
                    }

                    mouseIndex = value;
                    if (mouseIndex >= 0 && mouseIndex != SelectedIndex)
                    {
                        OnDrawItem(new DrawItemEventArgs(this.CreateGraphics(), Font, GetItemRectangle(value), value, DrawItemState.HotLight));
                    }

                    lastIndex = mouseIndex;
                }
            }
        }

        protected override void onm ouseMove(MouseEventArgs e)
        {
            base.OnMouseMove(e);
            MouseIndex = IndexFromPoint(e.Location);
        }

        protected override void onm ouseLeave(EventArgs e)
        {
            base.OnMouseLeave(e);
            MouseIndex = -1;
        }

其中 new DrawItemEventArgs(this.CreateGraphics(), Font, GetItemRectangle(value), value, DrawItemState.HotLight) 

第一個引數Graphics，也找了一會兒，后來看這篇：

https://www.cnblogs.com/yuanyeguhong/archive/2013/09/20/3330606.html

好了，至此，問題都已找到答案，再捋一下思路，把邏輯理順，擼代碼，除錯，OK！！！

主要代碼如下：

protected override void OnDrawItem(DrawItemEventArgs e)
        {
            base.OnDrawItem(e);

            BeforeDrawItem?.Invoke(this, Items, e);
            if (Items.Count == 0)
            {
                return;
            }

            bool otherState = e.State == DrawItemState.Grayed || e.State == DrawItemState.HotLight;
            if (!otherState)
            {
                e.DrawBackground();
            }

            if (e.Index < 0 || e.Index >= Items.Count)
            {
                return;
            }

            StringFormat sStringFormat = new StringFormat();
            sStringFormat.LineAlignment = StringAlignment.Center;

            bool isSelected = (e.State & DrawItemState.Selected) == DrawItemState.Selected;
            Color backColor = isSelected ? ItemSelectBackColor : BackColor;
            Color foreColor = isSelected ? ItemSelectForeColor : ForeColor;

            Rectangle rect = new Rectangle(e.Bounds.X, e.Bounds.Y, e.Bounds.Width - 1, e.Bounds.Height - 1);
            if (!otherState)
            {
                e.Graphics.FillRectangle(BackColor, e.Bounds);
                e.Graphics.FillRoundRectangle(backColor, rect, 5);
                e.Graphics.DrawString(Items[e.Index].ToString(), e.Font, foreColor, e.Bounds, sStringFormat);
            }
            else
            {
                if (e.State == DrawItemState.Grayed)
                {
                    backColor = BackColor;
                    foreColor = ForeColor;
                }

                if (e.State == DrawItemState.HotLight)
                {
                    backColor = HoverColor;
                    foreColor = ForeColor;
                }

                e.Graphics.FillRectangle(BackColor, e.Bounds);
                e.Graphics.FillRoundRectangle(backColor, rect, 5);
                e.Graphics.DrawString(Items[e.Index].ToString(), e.Font, foreColor, e.Bounds, sStringFormat);
            }

            AfterDrawItem?.Invoke(this, Items, e);
        }

看，DrawItemState.HotLight咱也給實作了，DrawItemState.Grayed 我是隨便選的狀態，區別于其他，

想看全部代碼，看我的開源專案吧，https://gitee.com/yhuse/SunnyUI ，哎，客官別走嘛，點個Star先，

原創文章，轉載請保留鏈接 Sunny's blog

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