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c# - 悬停时如何以不同方式绘制所有者绘制的 ListViewItem？

问题描述

下面是代码。我看到MouseMove事件并不总是被触发，特别是当鼠标移动非常快的时候，并且因为这两个项目可以同时被标记为hovered，所以我现在使用一个变量来保存最后一个悬停的项目，但是问题是重绘太多了。我还看到DrawListViewItemEventArgs.State属性就ShowKeyboardCues在它也应该包含Hot.

private void Form1_Load(object sender, EventArgs e)
{
    listView1.OwnerDraw = true;
    listView1.View = View.LargeIcon;
    listView1.DrawItem += ListView1_DrawItem;
    listView1.MouseMove += ListView1_MouseMove;

    for (int i = 1; i <= 6; ++i)
    {
        listView1.Items.Add($"item {i}", 0);
    }
}

private void ListView1_MouseMove(object sender, MouseEventArgs e)
{
    ListViewItem item = listView1.GetItemAt(e.X, e.Y);
    if (item != null)
    {
        if (LastHoveredItem != null && LastHoveredItem.Index == item.Index)
        {
            return;
        }
        listView1.RedrawItems(item.Index, item.Index, false);
    }
}

internal ListViewItem LastHoveredItem = null;

private void ListView1_DrawItem(object sender, DrawListViewItemEventArgs e)
{
    bool hot = e.Item.Bounds.Contains(listView1.PointToClient(Cursor.Position));

    if (LastHoveredItem != null)
    {
        listView1.RedrawItems(LastHoveredItem.Index, LastHoveredItem.Index, false);
    }

    if (hot)
    {
        LastHoveredItem = e.Item;
        e.Graphics.FillRectangle(Brushes.Green, e.Bounds);
    }
    else
    {
        LastHoveredItem = null;
    }

    e.DrawText();
}

标签： c#winformslistviewlistviewitem

解决方案

以下是一些新方法，并对现有方法进行了更新：

public Form1()
{
    InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{
    listView1.OwnerDraw = true;
    listView1.View = View.LargeIcon;
    listView1.DrawItem += ListView1_DrawItem;
    listView1.MouseEnter += ListView1_MouseEnter;
    listView1.MouseMove += ListView1_MouseMove;
    listView1.MouseLeave += ListView1_MouseLeave;

    for (int i = 1; i <= 10; ++i)
    {
        listView1.Items.Add($"item {i}", 0);
    }
}

private void ListView1_MouseEnter(object sender, EventArgs e)
{
    CheckHoveredAndInvalidate();
}

private void ListView1_MouseLeave(object sender, EventArgs e)
{
    RemoveHoveredAndInvalidate();
}

internal static Rectangle GetEntireItemBounds(ListViewItem it)
{
    return it.GetBounds(ItemBoundsPortion.Entire);
}

internal ListViewItem GetEntireItemAtCursorPosition()
{
    Point p = listView1.PointToClient(Cursor.Position);
    foreach (ListViewItem it in listView1.Items)
    {
        if (GetEntireItemBounds(it).Contains(p))
        {
            return it;
        }
    }
    return null;
}

private void ListView1_MouseMove(object sender, MouseEventArgs e)
{
    CheckHoveredAndInvalidate();
}

private void CheckHoveredAndInvalidate()
{
    ListViewItem item = GetEntireItemAtCursorPosition();

    if (item == null)
    {
        RemoveHoveredAndInvalidate();
    }
    else if (item != null)
    {
        if (LastHoveredItem != null)
        {
            if (LastHoveredItem != item)
            {
                ListViewItem item2 = LastHoveredItem;
                LastHoveredItem = item;
                listView1.Invalidate(GetEntireItemBounds(item2));
                listView1.Invalidate(GetEntireItemBounds(item));
            }
            else if (LastHoveredItem == item)
            {
            }
        }
        else if (LastHoveredItem == null)
        {
            LastHoveredItem = item;
            listView1.Invalidate(GetEntireItemBounds(item));
        }
    }
}

private void RemoveHoveredAndInvalidate()
{
    if (LastHoveredItem != null)
    {
        ListViewItem item2 = LastHoveredItem;
        LastHoveredItem = null;
        listView1.Invalidate(GetEntireItemBounds(item2));
    }
    else if (LastHoveredItem == null)
    {
    }
}

private void ListView1_DrawItem(object sender, DrawListViewItemEventArgs e)
{
    if (LastHoveredItem == e.Item)
    {
        e.Graphics.FillRectangle(Brushes.Yellow, e.Item.Bounds);
    }
    else
    {
        e.Graphics.FillRectangle(Brushes.Green, e.Item.Bounds);
    }
}

文字绘制部分已被省略。

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