封装avalonia指定组件允许拖动的工具类
创建Avalonia的MVVM项目，命名DragDemo ，然后将项目的Nuget包更新到预览版
<ItemGroup> <PackageReference Include="Avalonia" Version="11.0.0-preview5" /> <PackageReference Include="Avalonia.Desktop" Version="11.0.0-preview5" /> <!--Condition below is needed to remove Avalonia.Diagnostics package from build output in Release configuration.--> <PackageReference Condition="'$(Configuration)' == 'Debug'" Include="Avalonia.Diagnostics" Version="11.0.0-preview5" /> <PackageReference Include="Avalonia.ReactiveUI" Version="11.0.0-preview5" /> <PackageReference Include="XamlNameReferenceGenerator" Version="1.5.1" /> </ItemGroup> 更新完成以后ViewLocator和App.axaml会报错，
修改ViewLocator.cs为下面的代码
using System; using Avalonia.Controls; using Avalonia.Controls.Templates; using DragDemo.ViewModels; namespace DragDemo; public class ViewLocator : IDataTemplate { /// <summary> /// 将IControl修改成Control /// </summary> /// <param name="data"></param> /// <returns></returns> public Control Build(object data) { var name = data.GetType().FullName!.Replace("ViewModel", "View"); var type = Type.GetType(name); if (type != null) { return (Control)Activator.CreateInstance(type)!; } return new TextBlock { Text = "Not Found: " + name }; } public bool Match(object data) { return data is ViewModelBase; } } 添加Avalonia.Themes.Fluent，因为预览版本的包已经独立需要单独安装
<PackageReference Include="Avalonia.Themes.Fluent" Version="11.0.0-preview5" /> 打开App.axaml文件，修改为以下代码
<Application xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="using:DragDemo" RequestedThemeVariant="Light" x:Class="DragDemo.App"> <Application.DataTemplates> <local:ViewLocator/> </Application.DataTemplates> <Application.Styles> <FluentTheme DensityStyle="Compact"/> </Application.Styles> </Application> 打开Views/MainWindow.axaml
在头部添加以下代码，让窗口无边框，设置指定窗口Height="38" Width="471"，参数让其不要占用整个屏幕，
<Window xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:vm="using:DragDemo.ViewModels" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450" x:Class="DragDemo.Views.MainWindow" Icon="/Assets/avalonia-logo.ico" ExtendClientAreaToDecorationsHint="True" ExtendClientAreaChromeHints="NoChrome" ExtendClientAreaTitleBarHeightHint="-1" MaxHeight="38" MaxWidth="471" Title="DragDemo"> <Window.Styles> <Style Selector="Window"> <Setter Property="BorderThickness" Value="0"/> <Setter Property="Padding" Value="0"/> <Setter Property="Background" Value="Transparent"/> <Setter Property="BorderBrush" Value="Transparent"/> </Style> </Window.Styles> <Design.DataContext> <vm:MainWindowViewModel/> </Design.DataContext> <StackPanel> <StackPanel Opacity="0.1" Height="38" Width="471"> </StackPanel> <Border Name="Border" Width="471" CornerRadius="10" Opacity="1" Background="#FFFFFF"> <Button>按钮</Button> </Border> </StackPanel> </Window> 以下代码在上面窗口用于设置窗口无边框
<Window.Styles> <Style Selector="Window"> <Setter Property="BorderThickness" Value="0"/> <Setter Property="Padding" Value="0"/> <Setter Property="Background" Value="Transparent"/> <Setter Property="BorderBrush" Value="Transparent"/> </Style> </Window.Styles> 然后打开/Views/MainWindow.axaml.cs文件，将边框设置成无边框，并且设置窗体透明为WindowTransparencyLevel.Transparent
using Avalonia; using Avalonia.Controls; namespace DragDemo.Views; public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); this.TransparencyLevelHint = WindowTransparencyLevel.Transparent; ExtendClientAreaToDecorationsHint = true; WindowState = WindowState.Maximized; } } 效果图如下，因为限制了窗体最大大小，并且在按钮上面添加了透明区块，这样看起来就像是悬浮了
然后我们开始写指定组件拖动工具类，创建DragControlHelper.cs 以下就是封装的工具类 定义了一个ConcurrentDictionary静态参数，指定组件为Key ，Value为DragModule ，DragModule模型中定义了拖动的逻辑在调用StartDrag的时候传递需要拖动的组件，他会创建一个DragModule对象，创建的时候会创建定时器，当鼠标被按下时启动定时器，当鼠标被释放时定时器被停止，定时器用于平滑更新窗体移动，如果直接移动窗体会抖动。
using System; using System.Collections.Concurrent; using Avalonia; using Avalonia.Controls; using Avalonia.Input; using Avalonia.Threading; using Avalonia.VisualTree; namespace DragDemo; public class DragControlHelper { private static ConcurrentDictionary<Control, DragModule> _dragModules = new(); public static void StartDrag(Control userControl) { _dragModules.TryAdd(userControl, new DragModule(userControl)); } public static void StopDrag(Control userControl) { if (_dragModules.TryRemove(userControl, out var dragModule)) { dragModule.Dispose(); } } } class DragModule : IDisposable { /// <summary> /// 记录上一次鼠标位置 /// </summary> private Point? lastMousePosition; /// <summary> /// 用于平滑更新坐标的计时器 /// </summary> private DispatcherTimer _timer; /// <summary> /// 标记是否先启动了拖动 /// </summary> private bool isDragging = false; /// <summary> /// 需要更新的坐标点 /// </summary> private PixelPoint? _targetPosition; public Control UserControl { get; set; } public DragModule(Control userControl) { UserControl = userControl; // 添加当前控件的事件监听 UserControl.PointerPressed += OnPointerPressed; UserControl.PointerMoved += OnPointerMoved; UserControl.PointerReleased += OnPointerReleased; // 初始化计时器 _timer = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(10) }; _timer.Tick += OnTimerTick; } /// <summary> /// 计时器事件 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void OnTimerTick(object sender, EventArgs e) { var window = UserControl.FindAncestorOfType<Window>(); if (window != null && window.Position != _targetPosition) { // 更新坐标 window.Position = (PixelPoint)_targetPosition; } } private void OnPointerPressed(object sender, PointerPressedEventArgs e) { if (!e.GetCurrentPoint(UserControl).Properties.IsLeftButtonPressed) return; // 启动拖动 isDragging = true; // 记录当前坐标 lastMousePosition = e.GetPosition(UserControl); e.Handled = true; // 启动计时器 _timer.Start(); } private void OnPointerReleased(object sender, PointerReleasedEventArgs e) { if (!isDragging) return; // 停止拖动 isDragging = false; e.Handled = true; // 停止计时器 _timer.Stop(); } private void OnPointerMoved(object sender, PointerEventArgs e) { if (!e.GetCurrentPoint(UserControl).Properties.IsLeftButtonPressed) return; // 如果没有启动拖动，则不执行 if (!isDragging) return; var currentMousePosition = e.GetPosition(UserControl); var offset =currentMousePosition - lastMousePosition.Value; var window = UserControl.FindAncestorOfType<Window>(); if (window != null) { // 记录当前坐标 _targetPosition = new PixelPoint(window.Position.X + (int)offset.X, window.Position.Y + (int)offset.Y); } } public void Dispose() { _timer.Stop(); _targetPosition = null; lastMousePosition = null; } } 打开MainWindow.axaml.cs，修改成以下代码 ，在渲染成功以后拿到Border(需要移动的组件)，添加到DragControlHelper.StartDrag(border);中，然后再OnUnloaded的时候将Border再卸载掉
using Avalonia; using Avalonia.Controls; using Avalonia.Media; using Avalonia.Threading; namespace DragDemo.Views; public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); this.TransparencyLevelHint = WindowTransparencyLevel.Transparent; ExtendClientAreaToDecorationsHint = true; WindowState = WindowState.Maximized; } public override void Render(DrawingContext context) { base.Render(context); Dispatcher.UIThread.Post(() => { var border = this.Find<Border>("Border"); DragControlHelper.StartDrag(border); }); } protected override void OnUnloaded() { var border = this.Find<Border>("Border"); DragControlHelper.StopDrag(border); base.OnUnloaded(); } } 效果展示：
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