Xamarin.forms 如何使用带有动态时间的ProgressRing xamarin窗体显示计时器

我已经使用引用的代码实现了一个带有时间的进度环

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现在我想动态地绑定totaltime的值，这样当时间达到某个固定值时，进度环就开始进行。如何实现这一点？

由于

ConverterParameter

不是可绑定的属性，因此我们不能使用

绑定。但是我们可以尝试使用bindable属性自定义此标签，并将其自身传递给
转换器参数

自定义此标签，如：

public class MyLabel : Label
{
    public double TotalTime
    {
        set { SetValue(TotalTimeProperty, value); }
        get { return (double)GetValue(TotalTimeProperty); }
    }
    public static readonly BindableProperty TotalTimeProperty = BindableProperty.Create(nameof(TotalTime), typeof(double), typeof(MyLabel), default(double));
}

<local:MyLabel x:Name="MyLabel" 
                TotalTime="{Binding TotalTime}"
                Text="{Binding Source={x:Reference progressBar}, Path=Progress, Converter={StaticResource countDownTime}, ConverterParameter={x:Reference MyLabel}"
                HorizontalOptions ="Center"
                FontSize="20"
                FontFamily = "Helvetica Neue"
                TextColor = "Red" />

public class BindModel : INotifyPropertyChanged
{
    double totalTime;
    public double TotalTime
    {
        set
        {
            totalTime = value;
            onPropertyChanged("TotalTime");
        }
        get
        {
            return totalTime;
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    void onPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}
// And set this model as a BindingContext 
var model = new BindModel { TotalTime = 60000 };
BindingContext = model;

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    double time = 0;
    double myTotalTime = ((MyLabel)parameter).TotalTime;
    double.TryParse(myTotalTime.ToString(), out var totalTime);
    double.TryParse(value.ToString(), out var progress);
    time = progress <= double.Epsilon ? totalTime : (totalTime - (totalTime * progress));
    var timeSpan = TimeSpan.FromMilliseconds(time);
    return $"{timeSpan.Minutes:00;00}:{timeSpan.Seconds:00;00}";
}

然后我们可以在XAML中传递自身：

public class MyLabel : Label
{
    public double TotalTime
    {
        set { SetValue(TotalTimeProperty, value); }
        get { return (double)GetValue(TotalTimeProperty); }
    }
    public static readonly BindableProperty TotalTimeProperty = BindableProperty.Create(nameof(TotalTime), typeof(double), typeof(MyLabel), default(double));
}

<local:MyLabel x:Name="MyLabel" 
                TotalTime="{Binding TotalTime}"
                Text="{Binding Source={x:Reference progressBar}, Path=Progress, Converter={StaticResource countDownTime}, ConverterParameter={x:Reference MyLabel}"
                HorizontalOptions ="Center"
                FontSize="20"
                FontFamily = "Helvetica Neue"
                TextColor = "Red" />

public class BindModel : INotifyPropertyChanged
{
    double totalTime;
    public double TotalTime
    {
        set
        {
            totalTime = value;
            onPropertyChanged("TotalTime");
        }
        get
        {
            return totalTime;
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    void onPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}
// And set this model as a BindingContext 
var model = new BindModel { TotalTime = 60000 };
BindingContext = model;

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    double time = 0;
    double myTotalTime = ((MyLabel)parameter).TotalTime;
    double.TryParse(myTotalTime.ToString(), out var totalTime);
    double.TryParse(value.ToString(), out var progress);
    time = progress <= double.Epsilon ? totalTime : (totalTime - (totalTime * progress));
    var timeSpan = TimeSpan.FromMilliseconds(time);
    return $"{timeSpan.Minutes:00;00}:{timeSpan.Seconds:00;00}";
}

您的IValueConverter也应该是这样的：

public class MyLabel : Label
{
    public double TotalTime
    {
        set { SetValue(TotalTimeProperty, value); }
        get { return (double)GetValue(TotalTimeProperty); }
    }
    public static readonly BindableProperty TotalTimeProperty = BindableProperty.Create(nameof(TotalTime), typeof(double), typeof(MyLabel), default(double));
}

<local:MyLabel x:Name="MyLabel" 
                TotalTime="{Binding TotalTime}"
                Text="{Binding Source={x:Reference progressBar}, Path=Progress, Converter={StaticResource countDownTime}, ConverterParameter={x:Reference MyLabel}"
                HorizontalOptions ="Center"
                FontSize="20"
                FontFamily = "Helvetica Neue"
                TextColor = "Red" />

public class BindModel : INotifyPropertyChanged
{
    double totalTime;
    public double TotalTime
    {
        set
        {
            totalTime = value;
            onPropertyChanged("TotalTime");
        }
        get
        {
            return totalTime;
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    void onPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}
// And set this model as a BindingContext 
var model = new BindModel { TotalTime = 60000 };
BindingContext = model;

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    double time = 0;
    double myTotalTime = ((MyLabel)parameter).TotalTime;
    double.TryParse(myTotalTime.ToString(), out var totalTime);
    double.TryParse(value.ToString(), out var progress);
    time = progress <= double.Epsilon ? totalTime : (totalTime - (totalTime * progress));
    var timeSpan = TimeSpan.FromMilliseconds(time);
    return $"{timeSpan.Minutes:00;00}:{timeSpan.Seconds:00;00}";
}

公共对象转换（对象值、类型targetType、对象参数、CultureInfo区域性）
{
双倍时间=0；
double myTotalTime=（（MyLabel）参数）.TotalTime；
double.TryParse（myTotalTime.ToString（），out var totalTime）；
double.TryParse（value.ToString（），out var progress）；
时间=进度