MultiValueConverter Xamarin / WPF

如何解决MultiValueConverter Xamarin / WPF

在开发MultiValueConverter时，我遇到了一个奇怪的错误。

我在行上收到“无效的转换异常”：

int frameSize = (int)values[0] ; // <-- thows InvalidCast Exception

老实说，我无法确定原因。

public class SizeConverter : IMultiValueConverter
{
    public object Convert(object[] values,Type targettype,object parameter,CultureInfo culture)
    {
        if (values == null || values.Length <3 || values[2] == null || values[1] == null || values[0] == null)
            return 0;
        int numItems = (int)values[2];
        int separatorSize = (int)values[1]; 
        int frameSize = (int)values[0] ; // <-- thows InvalidCast Exception
        
        int totalSeparatorSize = (numItems - 1) * separatorSize;
        int remainingArea = frameSize - totalSeparatorSize;
        return remainingArea / numItems;
    }
    public object[] ConvertBack(object value,Type[] targettypes,CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

我在即时窗口中的Converter中验证了接收到的值[3]数组：

`{object[3]}
    [0]: 100
    [1]: 2
    [2]: 4`

这是调用代码MSTest [TestClass]：

[TestClass]
public class TestConverters
{
    [DaTarow(100,2,4)]
    [DataTestMethod]
    public void Test_Piece_Sizing(double frameSize,int separatorSize,int numItems)
    {
        var sizeConverter = new SizeConverter();
        object[] values = new object[] { frameSize,separatorSize,numItems };
        Assert.AreNotEqual(0,sizeConverter.Convert(values,typeof(int),null,System.Globalization.CultureInfo.CurrentCulture));
    }
}

================================================ ==============================

==================并且修复后的代码是：======================= =

    public class SizeConverter : IMultiValueConverter
{
    public object Convert(object[] values,CultureInfo culture)
    {
        if (values == null || values.Length <3 || values[2] == null || values[1] == null || values[0] == null)
            return 0;
        int numItems = (int)values[2];
        int separatorSize = (int)values[1]; 
        double frameSize = System.Convert.Todouble(values[0]) ;
        
        int totalSeparatorSize = (numItems - 1) * separatorSize;
        int remainingArea = System.Convert.ToInt32(frameSize) - totalSeparatorSize;
        return remainingArea / numItems;
    }
    public object[] ConvertBack(object value,CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

解决方法

在测试案例中，frameSize是double，而不是int。在您的int方法中将其更改为double或强制转换为Convert。

,

frameSize是double.just转换为double