如何限制用户输入EditText（Xamarin.Android）中小数点分隔符后的最大2位或3位数？

Question

我有以下课程：

public class DecimalFilter : Java.Lang.Object, IInputFilter
{
    //Pattern mPattern;
    String regex = "[0-9]+((\\.[0-9]{0," + (2 - 1) + "})?)||(\\.)?";
    public DecimalFilter(int digitsAfterZero)
    {
        //mPattern = Pattern.compile("[0-9]+((\\.[0-9]{0," + (digitsAfterZero - 1) + "})?)||(\\.)?");
        regex = "[0-9]+((\\.[0-9]{0," + (digitsAfterZero - 1) + "})?)||(\\.)?";
    }

    public Java.Lang.ICharSequence FilterFormatted(Java.Lang.ICharSequence source, int start, int end, ISpanned dest, int dstart, int dend)
    {
        if (System.Text.RegularExpressions.Regex.IsMatch(dest.ToString(), regex))
        {
            return new Java.Lang.String(string.Empty);
        }
        return null;
    }
}

我有两个EditText，我在其上设置过滤器：

discountEditText.SetFilters(new IInputFilter[] { new DecimalFilter(2) });
quantityEditText.SetFilters(new IInputFilter[] { new DecimalFilter(3) });

当我运行应用程序并尝试在这些EditTexts中输入内容时，我甚至无法输入单个数字。

Answer 1

试试这段代码：

public class DecimalFilter : Java.Lang.Object, IInputFilter
{
    String regex = "[0-9]+((\\.[0-9]{0," + (2 - 1) + "})?)||(\\.)?";
    public DecimalFilter(int digitsAfterZero)
    {
        //mPattern = Pattern.compile("[0-9]+((\\.[0-9]{0," + (digitsAfterZero - 1) + "})?)||(\\.)?"); 
        regex = "^[0-9]+(.[0-9]{0," + (digitsAfterZero-1)  + "})?$";

    }

    public Java.Lang.ICharSequence FilterFormatted(Java.Lang.ICharSequence source, int start, int end, ISpanned dest, int dstart, int dend)
    {

        if (System.Text.RegularExpressions.Regex.IsMatch(dest.ToString(), regex)||dest.ToString().Equals(""))
        {
            return new Java.Lang.String(source.ToString());
        }

        return new Java.Lang.String( string.Empty);
    }
}