在WPF中，如果窗口不在屏幕上，如何将其移动到屏幕上？

如果我有一个窗口，如何确保该窗口永远不会隐藏在屏幕之外？

这很重要，因为有时如果用户添加或删除监视器，如果我们记住了之前的位置，窗口可能会永久隐藏在屏幕之外。

我在用WPF + MVVM.

这个答案已经在大规模的现实世界应用中得到了测试。

从任何附加属性调用此函数可将窗口移回到可见屏幕上：

public static class ShiftWindowOntoScreenHelper
{
    /// <summary>
    ///     Intent:  
    ///     - Shift the window onto the visible screen.
    ///     - Shift the window away from overlapping the task bar.
    /// </summary>
    public static void ShiftWindowOntoScreen(Window window)
    {
        // Note that "window.BringIntoView()" does not work.                            
        if (window.Top < SystemParameters.VirtualScreenTop)
        {
            window.Top = SystemParameters.VirtualScreenTop;
        }

        if (window.Left < SystemParameters.VirtualScreenLeft)
        {
            window.Left = SystemParameters.VirtualScreenLeft;
        }

        if (window.Left + window.Width > SystemParameters.VirtualScreenLeft + SystemParameters.VirtualScreenWidth)
        {
            window.Left = SystemParameters.VirtualScreenWidth + SystemParameters.VirtualScreenLeft - window.Width;
        }

        if (window.Top + window.Height > SystemParameters.VirtualScreenTop + SystemParameters.VirtualScreenHeight)
        {
            window.Top = SystemParameters.VirtualScreenHeight + SystemParameters.VirtualScreenTop - window.Height;
        }

        // Shift window away from taskbar.
        {
            var taskBarLocation = GetTaskBarLocationPerScreen();

            // If taskbar is set to "auto-hide", then this list will be empty, and we will do nothing.
            foreach (var taskBar in taskBarLocation)
            {
                Rectangle windowRect = new Rectangle((int)window.Left, (int)window.Top, (int)window.Width, (int)window.Height);

                // Keep on shifting the window out of the way.
                int avoidInfiniteLoopCounter = 25;
                while (windowRect.IntersectsWith(taskBar))
                {
                    avoidInfiniteLoopCounter--;
                    if (avoidInfiniteLoopCounter == 0)
                    {
                        break;
                    }

                    // Our window is covering the task bar. Shift it away.
                    var intersection = Rectangle.Intersect(taskBar, windowRect);

                    if (intersection.Width < window.Width
                        // This next one is a rare corner case. Handles situation where taskbar is big enough to
                        // completely contain the status window.
                        || taskBar.Contains(windowRect))
                    {
                        if (taskBar.Left == 0)
                        {
                            // Task bar is on the left. Push away to the right.
                            window.Left = window.Left + intersection.Width;
                        }
                        else
                        {
                            // Task bar is on the right. Push away to the left.
                            window.Left = window.Left - intersection.Width;
                        }
                    }

                    if (intersection.Height < window.Height
                        // This next one is a rare corner case. Handles situation where taskbar is big enough to
                        // completely contain the status window.
                        || taskBar.Contains(windowRect))
                    {
                        if (taskBar.Top == 0)
                        {
                            // Task bar is on the top. Push down.
                            window.Top = window.Top + intersection.Height;
                        }
                        else
                        {
                            // Task bar is on the bottom. Push up.
                            window.Top = window.Top - intersection.Height;
                        }
                    }

                    windowRect = new Rectangle((int)window.Left, (int)window.Top, (int)window.Width, (int)window.Height);
                }
            }
        }
    }

    /// <summary>
    /// Returned location of taskbar on a per-screen basis, as a rectangle. See:
    /// https://stackoverflow.com/questions/1264406/how-do-i-get-the-taskbars-position-and-size/36285367#36285367.
    /// </summary>
    /// <returns>A list of taskbar locations. If this list is empty, then the taskbar is set to "Auto Hide".</returns>
    private static List<Rectangle> GetTaskBarLocationPerScreen()
    {
        List<Rectangle> dockedRects = new List<Rectangle>();
        foreach (var screen in Screen.AllScreens)
        {
            if (screen.Bounds.Equals(screen.WorkingArea) == true)
            {
                // No taskbar on this screen.
                continue;
            }

            Rectangle rect = new Rectangle();

            var leftDockedWidth = Math.Abs((Math.Abs(screen.Bounds.Left) - Math.Abs(screen.WorkingArea.Left)));
            var topDockedHeight = Math.Abs((Math.Abs(screen.Bounds.Top) - Math.Abs(screen.WorkingArea.Top)));
            var rightDockedWidth = ((screen.Bounds.Width - leftDockedWidth) - screen.WorkingArea.Width);
            var bottomDockedHeight = ((screen.Bounds.Height - topDockedHeight) - screen.WorkingArea.Height);
            if ((leftDockedWidth > 0))
            {
                rect.X = screen.Bounds.Left;
                rect.Y = screen.Bounds.Top;
                rect.Width = leftDockedWidth;
                rect.Height = screen.Bounds.Height;
            }
            else if ((rightDockedWidth > 0))
            {
                rect.X = screen.WorkingArea.Right;
                rect.Y = screen.Bounds.Top;
                rect.Width = rightDockedWidth;
                rect.Height = screen.Bounds.Height;
            }
            else if ((topDockedHeight > 0))
            {
                rect.X = screen.WorkingArea.Left;
                rect.Y = screen.Bounds.Top;
                rect.Width = screen.WorkingArea.Width;
                rect.Height = topDockedHeight;
            }
            else if ((bottomDockedHeight > 0))
            {
                rect.X = screen.WorkingArea.Left;
                rect.Y = screen.WorkingArea.Bottom;
                rect.Width = screen.WorkingArea.Width;
                rect.Height = bottomDockedHeight;
            }
            else
            {
                // Nothing found!
            }

            dockedRects.Add(rect);
        }

        if (dockedRects.Count == 0)
        {
            // Taskbar is set to "Auto-Hide".
        }

        return dockedRects;
    }
}

作为奖励，您可以实现自己的拖放，当拖动完成时，窗口将移回到屏幕上。

从用户的角度来看，如果窗口快速滑回可见区域而不是直接跳回到可见区域，会更直观，但至少这种方法得到了正确的结果。

/// <summary>
///     Intent: Add this Attached Property to any XAML element, to allow you to click and drag the entire window.
///     Essentially, it searches up the visual tree to find the first parent window, then calls ".DragMove()" on it. Once the drag finishes, it pushes
///     the window back onto the screen if part or all of it wasn't visible.
/// </summary>
public class EnableDragAttachedProperty
{
    public static readonly DependencyProperty EnableDragProperty = DependencyProperty.RegisterAttached(
        "EnableDrag",
        typeof(bool),
        typeof(EnableDragAttachedProperty),
        new PropertyMetadata(default(bool), OnLoaded));

    private static void OnLoaded(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
    {
        try
        {
            var uiElement = dependencyObject as UIElement;
            if (uiElement == null || (dependencyPropertyChangedEventArgs.NewValue is bool) == false)
            {
                return;
            }
            if ((bool)dependencyPropertyChangedEventArgs.NewValue == true)
            {
                uiElement.MouseMove += UIElement_OnMouseMove;
            }
            else
            {
                uiElement.MouseMove -= UIElement_OnMouseMove;
            }
        }
        catch (Exception ex)
        {
             // Log exception here.
        }
    }

    /// <summary>
    ///     Intent: Fetches the parent window, so we can call "DragMove()"on it. Caches the results in a dictionary,
    ///     so we can apply this same property to multiple XAML elements.
    /// </summary>
    private static void UIElement_OnMouseMove(object sender, MouseEventArgs mouseEventArgs)
    {
        try
        {
            var uiElement = sender as UIElement;
            if (uiElement != null)
            {
                Window window = GetParentWindow(uiElement);

                if (mouseEventArgs.LeftButton == MouseButtonState.Pressed)
                {
                    // DragMove is a synchronous call: once it completes, the drag is finished and the left mouse
                    // button has been released.
                    window?.DragMove();

                    // See answer in section 'Additional Links' below in the SO answer.
                //HideAndShowWindowHelper.ShiftWindowIntoForeground(window);

                    // When the use has finished the drag and released the mouse button, we shift the window back
                    // onto the screen, it it ended up partially off the screen.
                    ShiftWindowOntoScreenHelper.ShiftWindowOntoScreen(window);
                }
            }
        }
        catch (Exception ex)
        {
            _log.Warn($"Exception in {nameof(UIElement_OnMouseMove)}. " +
                      $"This means that we cannot shift and drag the Toast Notification window. " +
                      $"To fix, correct C# code.", ex);
        }
    }

    public static void SetEnableDrag(DependencyObject element, bool value)
    {
        element.SetValue(EnableDragProperty, value);
    }

    public static bool GetEnableDrag(DependencyObject element)
    {
        return (bool)element.GetValue(EnableDragProperty);
    }

    #region GetParentWindow
    private static readonly Dictionary<UIElement, Window> _parentWindow = new Dictionary<UIElement, Window>();
    private static readonly object _parentWindowLock = new object();

    /// <summary>
    ///     Intent: Given any UIElement, searches up the visual tree to find the parent Window.
    /// </summary>
    private static Window GetParentWindow(UIElement uiElement)
    {
        bool ifAlreadyFound;
        lock (_parentWindowLock)
        {
            ifAlreadyFound = _parentWindow.ContainsKey(uiElement) == true;
        }

        if (ifAlreadyFound == false)
        {
            DependencyObject parent = uiElement;
            int avoidInfiniteLoop = 0;
            // Search up the visual tree to find the first parent window.
            while ((parent is Window) == false)
            {
                parent = VisualTreeHelper.GetParent(parent);
                avoidInfiniteLoop++;
                if (avoidInfiniteLoop == 1000)
                {
                    // Something is wrong - we could not find the parent window.
                    return null;
                }
            }
            lock (_parentWindowLock)
            {
                _parentWindow[uiElement] = parent as Window;
            }
        }
        lock(_parentWindowLock)
        {
            return _parentWindow[uiElement];
        }
    }
    #endregion
}

附加链接

有关如何避免通知窗口被其他窗口隐藏的提示，请参阅我的回答：在 WPF 中将窗口置于最前面 https://stackoverflow.com/questions/257587/bring-a-window-to-the-front-in-wpf.