WPF 在 Windows 实现任务栏缩略图

摘要：先检查window是否为或imagePath是否为空。使用WindowInteropHelper获取window的句柄 (hwnd);注册窗口消息钩子，监听DWM消息；window.ShowInTaskbar = true;设置Window有任务栏图标，否则

WPF 在 Windows 实现任务栏缩略图

控件名：SetIconicThumbnail

作者：WPFDevelopersOrg - 驚鏵&赵嘉

原文链接[1]

：https://github.com/WPFDevelopersOrg/WPFDevelopers

码云链接[2]

：https://gitee.com/WPFDevelopersOrg/WPFDevelopers

框架支持.NET4 至 .NET8；

Visual Studio 2022;

在Windows Vista系统上，微软首次推出任务栏缩略图预览功能。Windows任务栏中，当我们将窗口最小化并将鼠标悬停在图标上，会显示一个窗口预览缩略图。通过Windows Dwm（Desktop Window Manager）[3]提供的API，我们可以自定义这个缩略图的内容，实现类似音乐播放器当前播放的音乐封面图。

先检查 window是否为或imagePath是否为空。

使用 WindowInteropHelper获取window的句柄 (hwnd);

注册窗口消息钩子，监听 DWM消息；

window.ShowInTaskbar = true;设置Window有任务栏图标，否则无法显示预览缩略图。

public static void SetIconicThumbnail(this Window window, string imagePath)
{
if (window == || string.IsOrWhiteSpace(imagePath)) return;
if (!File.Exists(imagePath)) return;
IntPtr hwnd = new WindowInteropHelper(window).Handle;
int size = Marshal.SizeOf(typeof(int));
IntPtr pbool = Marshal.AllocHGlobal(size);
try
{
Marshal.WriteInt32(pBool, 1);
Win32.DwmSetWindowAttribute(hwnd, DwmWindowAttributes.FORCE_ICONIC_REPRESENTATION, pBool, size);
Win32.DwmSetWindowAttribute(hwnd, DwmWindowAttributes.HAS_ICONIC_BITMAP, pBool, size);
}
finally
{
Marshal.FreeHGlobal(pBool);
}
var source = HwndSource.FromHwnd(hwnd);
if (source != )
{
source.AddHook(new HwndSourceHook((IntPtr hwnd2, int msg, IntPtr wParam, IntPtr lParam, refbool handled) =>
{
if (msg == WindowsMessageCodes.WM_DWMSENDICONICTHUMBNAIL)
{
int width = ((int)((((long)lParam) >> 16) & 0xFFFF));
int height = ((int)((long)lParam & 0xFFFF));
try
{
using (var bmp = new Bitmap(imagePath))
using (var resized = new Bitmap(bmp, new Size(width, height)))
{
IntPtr hBitmap = resized.GetHbitmap;
Win32.DwmSetIconicThumbnail(hwnd2, hBitmap, (int)DwmWindowAttributes.None);
Win32.DeleteObject(hBitmap);
}
}
catch (Exception ex)
{
thrownew Exception($"DwmSetIconicThumbnail error :{ex.Message}!");
}

handled =true;
}

return IntPtr.Zero;
}));
}
Win32.DwmInvalidateIconicBitmaps(hwnd);
window.ShowInTaskbar =true;
}

DwmSetWindowAttribute设置打开缩略图显示图片；

DwmSetIconicThumbnail设置自定义缩略图给任务栏；

DwmInvalidateIconicBitmaps通知DWM当前的缩略图无效，重新请求；

WM_DWMSENDICONICTHUMBNAILDWM向窗口发送消息，请求新的缩略图；

DeleteObject手动释放GDI，避免内存泄漏；

[DllImport(Gdi32)]
public static extern bool DeleteObject(IntPtr hObject);

[DllImport(DwmApi)]
public static extern int DwmSetIconicThumbnail(IntPtr hwnd, IntPtr hbmp, int dwSITFlags);

[DllImport(DwmApi)]
public static extern int DwmSetWindowAttribute(IntPtr hwnd, DwmWindowAttributes dwAttribute, IntPtr pvAttribute, int cbAttribute);

[DllImport(DwmApi)]
public static extern int DwmInvalidateIconicBitmaps(IntPtr hwnd);

internalclassWindowsMessageCodes
{
publicconstint WM_DWMSENDICONICTHUMBNAIL = 0x0323;
}

[Flags]
publicenum DwmWindowAttributes : uint
{
None = 0,
DISPLAYFRAME = 1,
FORCE_ICONIC_REPRESENTATION = 7,
HAS_ICONIC_BITMAP = 10
}

3. 新增 IconicThumbnailWindowExample.xaml

新增两个按钮切换图片，BtnPrevious_Click和BtnNext_Click。

Image控件用于显示任务栏的缩略图。

wd:Window
x:Class="WPFDevelopers.Sample.ExampleViews.IconicThumbnailWindowExample"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:converts="clr-namespace:WPFDevelopers.Sample.Converts"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:WPFDevelopers.Sample.ExampleViews"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:model="clr-namespace:WPFDevelopers.Sample.Models"
xmlns:wd="https://GitHub.com/WPFDevelopersOrg/WPFDevelopers"
Title="IconicThumbnailWindowExample"
Width="600"
Height="450"
Icon="pack://application:,,,/WPFDevelopers.Samples;component/WPFDevelopers.ico"
WindowStartupLocation="CenterScreen"
mc:Ignorable="d">
Grid
Grid.RowDefinitions
RowDefinitionHeight="7*" />
RowDefinitionHeight="3*" />
Grid.RowDefinitions
Image
x:Name="ImagePreview"
Width="200"
Height="200"
VerticalAlignment="Bottom" />
StackPanel
Grid.Row="1"
HorizontalAlignment="Center"
VerticalAlignment="Center"
wd:PanelHelper.Spacing="3"
Orientation="Horizontal">
Button
x:Name="BtnPrevious"
Width="50"
Height="50"
Click="BtnPrevious_Click">
wd:PathIconWidth="10" Kind="Previous" />
Button
Button
x:Name="BtnNext"
Width="50"
Height="50"
Click="BtnNext_Click">
wd:PathIconWidth="10" Kind="Next" />
Button
StackPanel
Grid
wd:Window

4. 新增 IconicThumbnailWindowExample.xaml.cs

BtnNext_Click

currentFileIndex = (currentFileIndex + 1) % fileList.Count;

通过代码实现图片循环切换：每次点击按钮时，currentFileIndex会增加1，如果超过了fileList的最大索引，回到第一个图片。。

BtnPrevious_Click

currentFileIndex = (currentFileIndex - 1 + fileList.Count) % fileList.Count;

currentFileIndex会减少1，并且如果当前索引小于0，回到最后一张图片。

using System;
using System.Collections.Generic;
using System.IO;
using System.Windows;
using System.Windows.Media.Imaging;
using WPFDevelopers.Helpers;

namespaceWPFDevelopers.Sample.ExampleViews
{
///
/// IconicThumbnailWindowExample.xaml 的交互逻辑
///
publicpartialclassIconicThumbnailWindowExample
{
private List fileList = new List;
privateint currentFileIndex = -1;
public IconicThumbnailWindowExample
{
InitializeComponent;
Loaded += IconicThumbnailWindowExample_Loaded;
}

private void IconicThumbnailWindowExample_Loaded(object sender, RoutedEventArgs e)
{
fileList.Clear;
currentFileIndex = -1;
var directorys = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "IconicThumbnail");
if (!Directory.Exists(directorys)) return;
string files = Directory.GetFiles(directorys);
fileList.AddRange(files);
}

private void BtnPrevious_Click(object sender, RoutedEventArgs e)
{
if (fileList.Count == 0) return;
currentFileIndex = (currentFileIndex + 1) % fileList.Count;
var img = fileList[currentFileIndex];
ImagePreview.Source = new BitmapImage(new Uri(img));
this.SetIconicThumbnail(img);
}
private void BtnNext_Click(object sender, RoutedEventArgs e)
{

currentFileIndex = (currentFileIndex - 1 + fileList.Count) % fileList.Count;

}
}
}