Avalonia 實現平滑拖動指定控制項

1.創建一個UserControl控制項，並且添加以下代碼

using System;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Input;
using Avalonia.Markup.Xaml;
using Avalonia.Media;
using Avalonia.Media.Imaging;
using Avalonia.Platform;
using Avalonia.Threading;
using Avalonia.VisualTree;

namespace Token;

/// <summary>
/// 實現拖動的控制項
/// </summary>
public partial class DragControls : UserControl
{
    /// <summary>
    /// 記錄上一次滑鼠位置
    /// </summary>
    private Point lastMousePosition;

    /// <summary>
    /// 用於平滑更新坐標的計時器
    /// </summary>
    private DispatcherTimer _timer;

    /// <summary>
    /// 標記是否先啟動了拖動
    /// </summary>
    private bool isDragging = false;

    /// <summary>
    /// 需要更新的坐標點
    /// </summary>
    private PixelPoint _targetPosition;

    public LoginStackPanelRight()
    {
        InitializeComponent();

        // 添加當前控制項的事件監聽
        PointerPressed += OnPointerPressed;
        PointerMoved += OnPointerMoved;
        PointerReleased += OnPointerReleased;

        // 初始化計時器
        _timer = new DispatcherTimer
        {
            Interval = TimeSpan.FromMilliseconds(10)
        };
        _timer.Tick += OnTimerTick;
    }

    /// <summary>
    /// 計時器事件
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void OnTimerTick(object sender, EventArgs e)
    {
        var window = this.FindAncestorOfType<Window>();
        if (window != null && window.Position != _targetPosition)
        {
            // 更新坐標
            window.Position = _targetPosition;
        }
    }

    private void InitializeComponent()
    {
        AvaloniaXamlLoader.Load(this);
    }

    private void OnPointerPressed(object sender, PointerPressedEventArgs e)
    {
        if (!e.GetCurrentPoint(this).Properties.IsLeftButtonPressed) return;
        // 啟動拖動
        isDragging = true;
        // 記錄當前坐標
        lastMousePosition = e.GetPosition(this);
        e.Handled = true;
        // 啟動計時器
        _timer.Start();
    }

    private void OnPointerReleased(object sender, PointerReleasedEventArgs e)
    {
        if (!isDragging) return;
        // 停止拖動
        isDragging = false;
        e.Handled = true;
        // 停止計時器
        _timer.Stop();
    }

    private void OnPointerMoved(object sender, PointerEventArgs e)
    {
        if (!e.GetCurrentPoint(this).Properties.IsLeftButtonPressed) return;
        
        // 如果沒有啟動拖動，則不執行
        if (!isDragging) return;

        var currentMousePosition = e.GetPosition(this);
        var offset = currentMousePosition - lastMousePosition;
        var window = this.FindAncestorOfType<Window>();
        if (window != null)
        {
            // 記錄當前坐標
            _targetPosition = new PixelPoint(window.Position.X + (int)offset.X,
                window.Position.Y + (int)offset.Y);
        }
    }
}

通過以上組件可以實現平滑拖動
效果如圖

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