ListBox更改特定项目预彩

Question

我正在努力为ListBox创建自定义功能。 我需要我的列表框来更改特定（“标记”）项目的预彩。 不要与选定的项目混淆。

所需的功能： 假设ListBox集合包含几个文件名。
当我双击一个项目时；该项目索引和对象存储在两个变量（索引和对象）中。
然后，这些变量将用于设置项目预彩（当未选择列表框项目时）。
剩余的项目和项目矩形应使用默认属性绘制 （在这种情况下，它们具有自己的颜色属性，可以进一步自定义）。

我的问题：

• 在负载
• 字符串时不绘制“怪异字符”
• 选择项目时， ；我正在绘制“标记”项目。

我真的很困惑。 MSDN文档并不清楚如何实现这一目标；也不是如何＆amp;当绘画事件发生时。

我一直在弄乱几种选择。但是，删除了所有内容，并回到了当前的代码，试图了解逻辑和行为。

第一次尝试代码（原始问题代码）：

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Custom_Controls.Controls
{
    internal class MyPlaylist : ListBox
    {
        public MyPlaylist()
        {
            SetStyle(ControlStyles.OptimizedDoubleBuffer, true);

            // Enable ListBox Customized Design
            DrawMode = DrawMode.OwnerDrawVariable;
            //SelectionMode = SelectionMode.MultiExtended;
        }

        #region <Custom Properties>
        private int markedIndex = -1;
        public int MarkedIndex
        {
            get { return markedIndex; }
            set { markedIndex = value; Invalidate(); }
        }

        private object markedItem = string.Empty;
        public object MarkedItem
        {
            get { return markedItem; }
            set
            {
                markedItem = value;
                Invalidate();
            }
        }

        private Color markedItemForeColor = Color.Red;
        public Color MarkedItemForeColor
        {
            get { return markedItemForeColor; }
            set { markedItemForeColor = value; Invalidate(); }
        }


        private Color markedItemBackColor = Color.DimGray;
        public Color MarkedItemBackColor
        {
            get { return markedItemBackColor; }
            set { markedItemBackColor = value; Invalidate(); }
        }


        private Color selectionBackColor = Color.DeepSkyBlue;
        public Color SelectionBackColor
        {
            get { return selectionBackColor; }
            set { selectionBackColor = value; Invalidate(); }
        }


        private Color selectionForeColor = Color.White;
        public Color SelectionForeColor
        {
            get { return selectionForeColor; }
            set { selectionForeColor = value; Invalidate(); }
        }
        #endregion


        
    protected override void OnDrawItem(DrawItemEventArgs e) // When Selected?
    {
        e.DrawBackground();
        e.DrawFocusRectangle();

        //// Improve Graphic Quality and Pixel Precision
        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
        e.Graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
        e.Graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;

        
        using (var defaultForeBrush = new SolidBrush(Color.White))
        using (var markForeBrush = new SolidBrush(markedItemForeColor))
        {
            // Iterate over all the items
            for (int i = 0; i < Items.Count; i++)
            {
                var item = Items[i];

                // Draw "Marked" Item
                if (i == markedIndex)
                { 
                    e.Graphics.DrawString(Items[markedIndex].ToString(), e.Font, markForeBrush, e.Bounds, StringFormat.GenericDefault); 
                }

                // Draw Remaining Items
                else
                {
                    e.Graphics.DrawString(item.ToString(), e.Font, markForeBrush, e.Bounds, StringFormat.GenericDefault);
                }

                // Draw Selection Rectangle
                // ...
            }
        }
    }        



        #region <Overriden Events>
        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
        }

        protected override void OnDoubleClick(EventArgs e)
        {
            base.OnDoubleClick(e);

            SetMarkedItem();
        }

        protected override void OnMouseDoubleClick(MouseEventArgs e)
        {
            base.OnMouseDoubleClick(e);

            SetMarkedItem();
        }


        #region <Methods>
        private void SetMarkedItem()
        {
            markedIndex = SelectedIndex;
            markedItem = SelectedItem;
        } 
        #endregion
    }
}

---

我的第二次尝试使用Jimi的帮助（当前代码）

更改：

• 我已经评论了Pinvoke LB_枚举wndproc，因为我无法使它起作用。
• 为了保持简单性：我删除了三元运营商（但是我喜欢Jimi的代码与它们交替使用颜色的方式）。
• SetMarker（）已恢复为以前的版本。标记的项目从未以这种方式绘制。
• 自定义属性没有为刷子提供其价值；因此，它们被暂时删除。

当前问题： 确切需要重新完成WNDProc以清除图纸（标记的项目）；也许要重新刷新控件，以便尽快更新标记。

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Custom_Controls.Controls
{
    internal class MyPlaylist : ListBox
    {
        #region <Constructor>
        public MyPlaylist()
        {
            SetStyle(ControlStyles.OptimizedDoubleBuffer, true);

            DrawMode = DrawMode.OwnerDrawVariable;

            BackColor = Color.FromArgb(255, 25, 25, 25);
            ForeColor = Color.White;
            BorderStyle = BorderStyle.FixedSingle;
        }
        #endregion


        #region <Fields>
        //private const int LB_RESETCONTENT = 0x0184;
        //private const int LB_DELETESTRING = 0x0182;

        //TextFormatFlags flags = TextFormatFlags.PreserveGraphicsClipping | TextFormatFlags.LeftAndRightPadding | TextFormatFlags.VerticalCenter;
        #endregion


        #region <Custom Properties>
        // Tip: Always Verify that the new Values are Different from the Old Ones

        private int markedIndex = -1;
        public int MarkedIndex
        {
            get { return markedIndex; }
            set
            {
                if (value != markedIndex)
                {
                    markedIndex = value;
                    Invalidate();
                }
            }
        }

        // Read-only: just return the marked Item, set it using the Index only
        public object MarkedItem
        {
            get { return Items[markedIndex]; }
        }
        #endregion


        #region <Overriden Events>
        protected override void OnDrawItem(DrawItemEventArgs e)
        {
            if (Items.Count == 0) return;

            // Draw Selection:
            if (e.State.HasFlag(DrawItemState.Focus) || e.State.HasFlag(DrawItemState.Selected))
            {
                using (var brush = new SolidBrush(Color.FromArgb(255, 52, 52, 52)))
                {
                    // Background Rectangle
                    e.Graphics.FillRectangle(brush, e.Bounds);

                    // Item Text : Marked Item
                    if (e.Index == markedIndex)
                    {
                        TextRenderer.DrawText(e.Graphics, GetItemText(Items[e.Index]), Font, e.Bounds, Color.Red, flags);
                    }
                    
                    // Other Items (Except Marked)
                    else
                    {
                        TextRenderer.DrawText(e.Graphics, GetItemText(Items[e.Index]), Font, e.Bounds, Color.White, flags);
                    }
                }
            }

            // Draw Unselected:
            else
            {
                using (var brush = new SolidBrush(BackColor))
                using (var markedBrush = new SolidBrush(Color.Khaki))
                {
                    e.Graphics.FillRectangle(brush, e.Bounds);
                    TextRenderer.DrawText(e.Graphics, GetItemText(Items[e.Index]), Font, e.Bounds, Color.White, flags);
                }

                // Draw (Unselected) Marked Item
                if (markedIndex > -1 && e.Index == markedIndex)
                {
                    TextRenderer.DrawText(e.Graphics, GetItemText(Items[e.Index]), Font, e.Bounds, Color.Red, flags);
                }
            }

            e.DrawFocusRectangle();

            base.OnDrawItem(e);
        }

        // Set the Height of the Item (Width: only if needed).
        // This is the Standard Value (Modify as required)
        protected override void OnMeasureItem(MeasureItemEventArgs e)
        {
            if (Items.Count > 0)
            {
                e.ItemHeight = Font.Height + 4; // 4 = Text vs Item Rectangle Margin
            }

            base.OnMeasureItem(e);
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
        }

        protected override void OnDoubleClick(EventArgs e)
        {
            base.OnDoubleClick(e);

            SetMarkedItem();
        }

        protected override void OnMouseDoubleClick(MouseEventArgs e)
        {
            base.OnMouseDoubleClick(e);

            if (e.Button == MouseButtons.Left)
            {
                SetMarkedItem();
            }
        }
        #endregion

        #region <Methods>
        /// <summary>
        /// WndProc is Overridden in order to Intercept the LB_RESETCONTENT (sent when the ObjectCollection is cleared);<br/> 
        /// and the LB_DELETESTRING (sent when an Item is removed).
        /// This is done to reset the marked Item when the list is cleared or the marked Item is removed (otherwise an Item will remain marked when it shouldn't).
        /// </summary>
        /// <param name="m"></param>
        //protected override void WndProc(ref Message m)
        //{
        //    switch (m.Msg)
        //    {
        //        // List Cleared
        //        case LB_RESETCONTENT:
        //            markedIndex = -1;
        //            break;

        //        // Item Deleted
        //        case LB_DELETESTRING:
        //            if (markedIndex == m.WParam.ToInt32())
        //            {
        //            markedIndex = -1;
        //            }
        //            break;
        //    }
        //}

        private void SetMarkedItem()    // Current Block
        {
            markedIndex = SelectedIndex;
        }

        // Previous Code Line (By Jimmy; using Ternary Operator) <----------------------------------------
        //private void SetMarkedItem() => MarkedIndex = markedIndex == SelectedIndex ? -1 : SelectedIndex;
        #endregion
    }
}

---

有用的相关内容

listbox：listbox：pinvoke lb_（enums lb_（enums）

如何将多行文本添加到列表框项目

Answer 1

该示例类包含使列表作为标准列表框起作用所需的调整，但使用问题中描述的增强功能。
另请参见代码中的评论。

• graphics.drawString（）：这将为渲染列表项目提供更多天然。无需使用抗异化。
• onMeasureItem 也被压倒了为项目提供自定义高度（可选的宽度 - 严格要求）。它设置为 ListBox.font.height + 4 （pretty Standard）;根据需要进行修改。
• OnDrawItem（）可以纠正以处理自定义选择颜色和标记项目的颜色。请注意，此方法是每项一次调用一次的，因此您不必每次循环整个集合，只需用正确的颜色绘制当前项目即可。
• setMarkedItem（）被修改以切换标记项目的状态，以防双击它两次。
• wndproc 被覆盖为 Intercept lb_resetContent （当清除 Objectcollection 时发送）和 lb_deletestring （删除项目时发送）。这样做是为了在清除列表或删除标记的项目时重置标记的项目（否则，在不应该的情况下将保持标记）。
• 设置属性值时，请始终验证新值不等于旧值，然后再调用 invalidate（）（或任何其他方法 - 或属性设置程序）无缘无故。
• 一些小更改，请参阅代码。

---

public class MyPlaylist : ListBox {

    private const int LB_DELETESTRING = 0x0182;
    private const int LB_RESETCONTENT = 0x0184;

    TextFormatFlags flags = TextFormatFlags.PreserveGraphicsClipping |
                            TextFormatFlags.LeftAndRightPadding |
                            TextFormatFlags.VerticalCenter;

    public MyPlaylist()
    {
        SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
        DrawMode = DrawMode.OwnerDrawVariable;
    }

    protected override void WndProc(ref Message m)
    {
        switch (m.Msg) {
            // List cleared
            case LB_RESETCONTENT:
                markedIndex = -1;
                break;
            // Item deleted
            case LB_DELETESTRING:
                if (markedIndex == m.WParam.ToInt32()) {
                    markedIndex = -1;
                }
                break;
        }
        base.WndProc(ref m);
    }

    private int markedIndex = -1;
    public int MarkedIndex {
        get => markedIndex;
        set {
            if (value != markedIndex) {
                markedIndex = value;
                Invalidate();
            }
        }
    }

    // Read-only: just return the marked Item, set it using the Index only
    [Browsable(false)]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public object MarkedItem {
        get => Items[markedIndex];
    }

    // Always verify that the new value is different from the old one
    private Color markedItemForeColor = Color.Orange;
    public Color MarkedItemForeColor {
        get => markedItemForeColor;
        set { 
            if (value != markedItemForeColor) {
                markedItemForeColor = value;
                Invalidate();
            }
        }
    }

    private Color markedItemBackColor = Color.DimGray;
    public Color MarkedItemBackColor {
        get => markedItemBackColor;
        set { 
            if (value != markedItemBackColor) {
                markedItemBackColor = value;
                Invalidate();
            }
        }
    }

    private Color selectionBackColor = Color.DeepSkyBlue;
    public Color SelectionBackColor {
        get => selectionBackColor;
        set { 
            if (value != selectionBackColor) {
                selectionBackColor = value;
                Invalidate();
            }
        }
    }

    private Color selectionForeColor = Color.White;
    public Color SelectionForeColor {
        get => selectionForeColor;
        set { 
            if (value != selectionForeColor) {
                selectionForeColor = value;
                Invalidate();
            }
        }
    }

    // Use TextRenderer to draw the Items - no anti-aliasing needed
    protected override void OnDrawItem(DrawItemEventArgs e)
    {
        if (Items.Count == 0) return;
        if (e.State.HasFlag(DrawItemState.Focus) || e.State.HasFlag(DrawItemState.Selected)) {
            using (var brush = new SolidBrush(selectionBackColor)) {
                e.Graphics.FillRectangle(brush, e.Bounds);
            }
            TextRenderer.DrawText(e.Graphics, GetItemText(Items[e.Index]), Font, e.Bounds, selectionForeColor, flags);
        }
        else {
            var color = markedIndex != -1 && markedIndex == e.Index ? markedItemBackColor : BackColor;
            using (var brush = new SolidBrush(color)) {
                e.Graphics.FillRectangle(brush, e.Bounds);
            }
            var foreColor = markedIndex == e.Index ? markedItemForeColor : ForeColor;
            TextRenderer.DrawText(e.Graphics, GetItemText(Items[e.Index]), Font, e.Bounds, foreColor, flags);
        }
        e.DrawFocusRectangle();
        base.OnDrawItem(e);
    }

    // Set the Height (the Width only if needed) of the Item
    // This is the standard value, modify as required
    protected override void OnMeasureItem(MeasureItemEventArgs e)
    {
        if (Items.Count > 0) {
            e.ItemHeight = Font.Height + 4;
        }
        base.OnMeasureItem(e);
    }

    protected override void OnMouseDoubleClick(MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left) {
            SetMarkedItem();
        }
        base.OnMouseDoubleClick(e);
    }

    private void SetMarkedItem() => MarkedIndex = markedIndex == SelectedIndex ? -1 : SelectedIndex;
}