WPF 滚动查看器和平移

Question

我有一个带ScrollViewer的Window，在ScrollViewer里面有一个Rectangle.现在我添加了代码来拖动工作正常的Rectangle。但是我不知道当Rectangle移动到视图之外时如何显示Scrollbars。我以为这会自动发生，事实并非如此？

这是我的 XAML：

<Window x:Class="WpfApp4.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp4"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <ScrollViewer Name="_scrollViewer" CanContentScroll="True" 
                  HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
        <Rectangle Name="_myRect" Width="100" Height="100" Fill="Blue"/>
    </ScrollViewer>
</Window>

以及背后的代码：

public partial class MainWindow : Window
{
    private Point _origin;
    private Point _start;
    private ScaleTransform _scaleTransform = new ScaleTransform();
    private TranslateTransform _translateTransform = new TranslateTransform();
    public MainWindow()
    {
        InitializeComponent();
        var group = new TransformGroup();
        group.Children.Add(_scaleTransform);
        group.Children.Add(_translateTransform);  
        _myRect.RenderTransform = group;
        // Hook up events
        _myRect.MouseLeftButtonDown += _myRect_MouseLeftButtonDown;
        _myRect.MouseLeftButtonUp += _myRect_MouseLeftButtonUp;
        _myRect.MouseMove += _myRect_MouseMove;
    }
    private void _myRect_MouseMove(object sender, MouseEventArgs e)
    {
        if (_myRect.IsMouseCaptured)
        {
            Vector v = _start - e.GetPosition(this);
            _translateTransform.X = _origin.X - v.X;
            _translateTransform.Y = _origin.Y - v.Y;
        }
    }
    private void _myRect_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        _myRect.ReleaseMouseCapture();
        this.Cursor = Cursors.Arrow;
    }
    private void _myRect_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        _start = e.GetPosition(this);
        _origin = new Point(_translateTransform.X, _translateTransform.Y);
        Cursor = Cursors.Hand;
        _myRect.CaptureMouse();
    }
}

[更新]：因此，根据我得到的输入，我将 XAML 和后面的代码更改为以下内容 - 但仍然没有滚动条？

<Window x:Class="WpfApp4.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp4"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <ScrollViewer Name="_scrollViewer" CanContentScroll="True" 
                  HorizontalScrollBarVisibility="Visible" VerticalScrollBarVisibility="Visible">
        <Canvas Name="_myCanvas">
            <Rectangle Name="_myRect" Width="100" Height="100" Fill="Blue" Canvas.Left="305" Canvas.Top="129"/>
        </Canvas>
    </ScrollViewer>
</Window>

代码隐藏：

public partial class MainWindow : Window
{
    private Point _start;
    public MainWindow()
    {
        InitializeComponent();
        // Hook up events
        _myRect.MouseLeftButtonDown += _myRect_MouseLeftButtonDown;
        _myRect.MouseLeftButtonUp += _myRect_MouseLeftButtonUp;
        _myRect.MouseMove += _myRect_MouseMove;
    }
    private void _myRect_MouseMove(object sender, MouseEventArgs e)
    {
        if (_myRect.IsMouseCaptured)
        {
            var canvasRelativePosition = e.GetPosition(_myCanvas);
            Debug.WriteLine($"New Position: {canvasRelativePosition}");
            Canvas.SetTop(_myRect, canvasRelativePosition.Y - _start.Y);
            Canvas.SetLeft(_myRect, canvasRelativePosition.X - _start.X);
        }
    }
    private void _myRect_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        _myRect.ReleaseMouseCapture();
        this.Cursor = Cursors.Arrow;
    }
    private void _myRect_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        _start = e.GetPosition(_myRect);
        Debug.WriteLine($"Start Position: {_start}");
        Cursor = Cursors.Hand;
        _myRect.CaptureMouse();
    }
}

Answer 1

如果您希望转换影响布局，则必须使用 LayoutTransofrm 。 RenderTransform只会改变外观。

与元素 LayoutTransform 关联的任何转换 财产将对后续的措施和安排产生影响 步骤。而渲染变换不会对 布局过程，只会影响渲染。

在此处阅读更多内容。

但是，LayoutTransform忽略了TranslateTransform

LayoutTransform 忽略 TranslateTransform 操作。这是因为 框架元素的子元素的布局系统行为 自动将任何偏移校正到缩放或旋转的位置 元素，以加入父元素的布局和坐标系。

在此处阅读更多内容

所有这些都意味着，要实现移动元素，您不能使用 Transforms .你可以尝试手动改变元素的位置(Margin、Canvas.Left/Right或其他想法(。