无论缩放级别如何，如何以始终位于地图中心的方式绘制标记？答案

【问题标题】：How can I draw a marker in a way that will always be at the center of the map regardless of the zoom level?无论缩放级别如何，如何以始终位于地图中心的方式绘制标记？
【发布时间】：2013-12-29 07:03:13
【问题描述】：

我正在向地图中心添加一个标记。然而，随着地图缩放级别的变化，中心正在从“原始”地图中心移动（标记也是如此）。

无论缩放级别如何，如何以始终位于地图中心的方式绘制标记？

似乎 PositionOrigin 设置为 (0.5, 0.5 ) 没有做它应该做的事情，即以画布中心位于 GeoCoordinate“位置”输入变量的方式绘制画布。

我绘制标记的代码如下：

    private void AddMarkerToMap( String symbol, GeoCoordinate location )
        {
        if ( _markerLayer != null )
            {
            Map1.Layers.Remove( _markerLayer );
            _markerLayer = null;
            }

        _markerLayer = new MapLayer();
        var mapCenterMarker = new MapOverlay
                            {
                                GeoCoordinate = location
                            };

        var canvas = new Canvas();
        //canvas.Opacity = 0.5;

        var circhegraphic = new Ellipse();
        circhegraphic.Fill = new SolidColorBrush( Color.FromArgb( 0x44, 0x00, 0xFF, 0x00 ) );
        circhegraphic.Stroke = new SolidColorBrush( Color.FromArgb( 0xFF, 0x00, 0x00, 0xFF ) );
        circhegraphic.StrokeThickness = 4;
        circhegraphic.Opacity = 0.7;
        circhegraphic.Height = 40;
        circhegraphic.Width = 40;
        canvas.Children.Add( circhegraphic );

        var textBlock = new TextBlock
            {
                Text = symbol,
                HorizontalAlignment = HorizontalAlignment.Center,
                VerticalAlignment = VerticalAlignment.Center,
                FontWeight = FontWeights.ExtraBold,
                Foreground = new SolidColorBrush( Color.FromArgb( 0xFF, 0xFF, 0x00, 0x00 ) )
            };
        Canvas.SetLeft( textBlock, 13 );
        Canvas.SetTop( textBlock, 4 );
        Canvas.SetZIndex( textBlock, 5 );
        canvas.Children.Add( textBlock );

        mapCenterMarker.Content = canvas;
        mapCenterMarker.PositionOrigin = new Point( 0.5, 0.5 );

        _markerLayer.Add( mapCenterMarker );
        Map1.Layers.Add( _markerLayer );
        }

谢谢，

【问题讨论】：

标签： c# windows-phone-8 here-api

【解决方案1】：

问题出在画布上，改成这样的网格：

    private void AddMarkerToMap( String symbol, GeoCoordinate location )
        {
        if ( _markerLayer != null )
            {
            Map1.Layers.Remove( _markerLayer );
            _markerLayer = null;
            }

        _markerLayer = new MapLayer();
        var mapCenterMarker = new MapOverlay();
        var grid = new Grid();

        var circhegraphic = new Ellipse();
        circhegraphic.Fill = new SolidColorBrush( Color.FromArgb( 0x44, 0x00, 0xFF, 0x00 ) );
        circhegraphic.Stroke = new SolidColorBrush( Color.FromArgb( 0xFF, 0x00, 0x00, 0xFF ) );
        circhegraphic.StrokeThickness = 4;
        circhegraphic.Opacity = 0.7;
        circhegraphic.Height = 40;
        circhegraphic.Width = 40;
        grid.Children.Add( circhegraphic );

        var textBlock = new TextBlock
            {
                Text = symbol,
                HorizontalAlignment = HorizontalAlignment.Center,
                VerticalAlignment = VerticalAlignment.Center,
                FontWeight = FontWeights.ExtraBold,
                FontSize = 14,
                Foreground = new SolidColorBrush( Color.FromArgb( 0xFF, 0xFF, 0x00, 0x00 ) )
            };
        grid.Children.Add( textBlock );

        mapCenterMarker.GeoCoordinate = location;
        mapCenterMarker.Content = grid;
        mapCenterMarker.PositionOrigin = new Point( 0.5, 0.5 );

        _markerLayer.Add( mapCenterMarker );
        Map1.Layers.Add( _markerLayer );
        }

虽然我不确定为什么 Canvas 是个问题。

【讨论】：