在Xamarin Forum Discussion的帮助下，我实现了。在实施之前阅读广告了解完整的讨论。感谢“Slava Chernikoff”、“Emanuele Sabetta”、“Mirza Sikander”、“Satish”的讨论和你们的分享代码。
Setp 1：在 PCL 中创建一个 Helper 类并从 nugget 安装 NGraphics 包。
public class CartIconHelper
{
private static Graphic _svgGraphic = null;
public const string ResourcePath = "ToolBarAndroidBadge.Resources.cartIcon.svg";
private static PathOp[] RoundRect(NGraphics.Rect rect, double radius)
{
return new PathOp[]
{
new NGraphics.MoveTo(rect.X + radius, rect.Y),
new NGraphics.LineTo(rect.X + rect.Width - radius, rect.Y),
new NGraphics.ArcTo(new NGraphics.Size(radius, radius), true, false, new NGraphics.Point(rect.X + rect.Width, rect.Y + radius)),
new NGraphics.LineTo(rect.X + rect.Width, rect.Y + rect.Height - radius),
new NGraphics.ArcTo(new NGraphics.Size(radius, radius), true, false, new NGraphics.Point(rect.X + rect.Width - radius, rect.Y + rect.Height)),
new NGraphics.LineTo(rect.X + radius, rect.Y + rect.Height),
new NGraphics.ArcTo(new NGraphics.Size(radius, radius), true, false, new NGraphics.Point(rect.X, rect.Y + rect.Height - radius)),
new NGraphics.LineTo(rect.X, rect.Y + radius), new NGraphics.ArcTo(new NGraphics.Size(radius, radius), true, false, new NGraphics.Point(rect.X + radius, rect.Y)),
new NGraphics.ClosePath()
};
}
public static string DrawCartIcon(int count, string path, double iconSize = 30, double scale = 2, string fontName = "Arial", double fontSize = 12, double textSpacing = 4)
{
var service = DependencyService.Get<IService>();
var canvas = service.GetCanvas();
if (_svgGraphic == null) using (var stream = typeof(CartIconHelper).GetTypeInfo().Assembly.GetManifestResourceStream(path))
_svgGraphic = new SvgReader(new StreamReader(stream)).Graphic;
//st = ReadFully(stream);
var minSvgScale = Math.Min(canvas.Size.Width / _svgGraphic.Size.Width, canvas.Size.Height / _svgGraphic.Size.Height) / 1.15;
var w = _svgGraphic.Size.Width / minSvgScale;
var h = _svgGraphic.Size.Height / minSvgScale;
_svgGraphic.ViewBox = new NGraphics.Rect(0, -14, w, h);
_svgGraphic.Draw(canvas);
if (count > 0)
{
var text = count > 99 ? "99+" : count.ToString();
var font = new NGraphics.Font(fontName, fontSize);
var textSize = canvas.MeasureText(text, font);
var textRect = new NGraphics.Rect(canvas.Size.Width - textSize.Width - textSpacing, textSpacing, textSize.Width, textSize.Height);
if (count < 10)
{
var side = Math.Max(textSize.Width, textSize.Height);
var elipseRect = new NGraphics.Rect(canvas.Size.Width - side - 2 * textSpacing, 0, side + 2 * textSpacing, side + 2 * textSpacing);
canvas.FillEllipse(elipseRect, NGraphics.Colors.Red);
textRect -= new NGraphics.Point(side - textSize.Width, side - textSize.Height) / 2.0;
}
else
{
var elipseRect = new NGraphics.Rect(textRect.Left - textSpacing, textRect.Top - textSpacing, textRect.Width + 2 * textSpacing, textSize.Height + 2 * textSpacing);
canvas.FillPath(RoundRect(elipseRect, 6), NGraphics.Colors.Red);
}
var testReact1= new NGraphics.Rect(20,12,0,0);
// canvas.DrawText(text, textRect + new NGraphics.Point(0, textSize.Height), font, NGraphics.TextAlignment.Center, NGraphics.Colors.Black);
canvas.DrawText("5", testReact1, font, NGraphics.TextAlignment.Left, NGraphics.Colors.White);
}
service.SaveImage(canvas.GetImage());
string imagePath = service.GetImage();
return imagePath;
// return st;
}
}
第 2 步：在 PCL 中创建到 IService 的接口
public interface IService
{
IImageCanvas GetCanvas();
void SaveImage(NGraphics.IImage image);
string GetImage();
}
第 3 步：在您的 Android 项目中实现此接口
class CanvasServices:IService
{
private readonly AndroidPlatform _platform;
public CanvasServices()
{
_platform = new AndroidPlatform();
}
public void SaveImage(IImage image)
{
var dir = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
var filePath = System.IO.Path.Combine(dir, "cart.png");
var stream = new FileStream(filePath, FileMode.Create);
image.SaveAsPng(stream);
//bitmap.Compress(image., 100, stream);
stream.Close();
}
public string GetImage()
{
var dir = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
var filePath = System.IO.Path.Combine(dir, "cart.png");
using (var streamReader = new StreamReader(filePath))
{
string content = streamReader.ReadToEnd();
System.Diagnostics.Debug.WriteLine(content);
}
return filePath;
}
public IImageCanvas GetCanvas()
{
NGraphics.Size size = new NGraphics.Size(30);
return _platform.CreateImageCanvas(size);
}
public NGraphics.AndroidPlatform GetPlatform()
{
return _platform;
}
}
Setp 4：现在，在您的 PCL 项目中使用 CartIcon Helper 在 TabBarItem 中显示徽章。
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
var imagePath = CartIconHelper.DrawCartIcon(2, "ToolBarAndroidBadge.Resources.cartIcon.svg");
string deviceSepecificFolderPath = Device.OnPlatform(null, imagePath, null);
object convertedObject = new FileImageSourceConverter().ConvertFromInvariantString(deviceSepecificFolderPath);
FileImageSource fileImageSource = (FileImageSource)convertedObject;
ToolbarItem cartItem = new ToolbarItem();
cartItem.Text = "My Cart";
cartItem.Order = ToolbarItemOrder.Primary;
cartItem.Icon = fileImageSource;
ToolbarItems.Add(cartItem);
}
}