xamarin.forms - Xamarin Forms 滑动按钮

Question

我希望在我的应用程序中添加一个滑动功能，该功能与(旧的？)iPhone 上的解锁机制几乎相同(参见图片)。




我正在努力解决如何在跨平台解决方案上实现这一点。我的直接想法是使用 slider 和自定义渲染器，但不确定如果用户在完成幻灯片之前放开，如何创建捕捉开始的功能。如果有人可以协助该功能，或者他们对如何实现此功能有更好的建议，将不胜感激。

Answer 1

除非和直到 - 您确实需要为每个平台提供特别原生的外观；您几乎可以使用 PanGestureRecognizer 编写自己的自定义 slider 控件, 和 AbsoluteLayout ( 无需任何自定义渲染器 )。对于捕捉效果，您可以使用 Translation animation与 Cubic easing影响。

例如，您可以定义一个控件如下；此示例控件扩展了 AbsoluteLayout同时允许您定义代表拇指和轨迹栏的自己的控件。它还创建了一个几乎不可见的最顶层来充当平移手势监听器。一旦手势完成，它会检查滑动是否完成(即轨迹栏的整个宽度) - 然后提升 SlideCompleted事件。

public class SlideToActView : AbsoluteLayout
{
    public static readonly BindableProperty ThumbProperty =
        BindableProperty.Create(
            "Thumb", typeof(View), typeof(SlideToActView),
            defaultValue: default(View), propertyChanged: OnThumbChanged);

    public View Thumb
    {
        get { return (View)GetValue(ThumbProperty); }
        set { SetValue(ThumbProperty, value); }
    }

    private static void OnThumbChanged(BindableObject bindable, object oldValue, object newValue)
    {
        ((SlideToActView)bindable).OnThumbChangedImpl((View)oldValue, (View)newValue);
    }

    protected virtual void OnThumbChangedImpl(View oldValue, View newValue)
    {
        OnSizeChanged(this, EventArgs.Empty);
    }

    public static readonly BindableProperty TrackBarProperty =
        BindableProperty.Create(
            "TrackBar", typeof(View), typeof(SlideToActView),
            defaultValue: default(View), propertyChanged: OnTrackBarChanged);

    public View TrackBar
    {
        get { return (View)GetValue(TrackBarProperty); }
        set { SetValue(TrackBarProperty, value); }
    }

    private static void OnTrackBarChanged(BindableObject bindable, object oldValue, object newValue)
    {
        ((SlideToActView)bindable).OnTrackBarChangedImpl((View)oldValue, (View)newValue);
    }

    protected virtual void OnTrackBarChangedImpl(View oldValue, View newValue)
    {
        OnSizeChanged(this, EventArgs.Empty);
    }

    private PanGestureRecognizer _panGesture = new PanGestureRecognizer();
    private View _gestureListener;
    public SlideToActView()
    {
        _panGesture.PanUpdated += OnPanGestureUpdated;
        SizeChanged += OnSizeChanged;

        _gestureListener = new ContentView { BackgroundColor = Color.White, Opacity = 0.05 };
        _gestureListener.GestureRecognizers.Add(_panGesture);
    }

    public event EventHandler SlideCompleted;

    private const double _fadeEffect = 0.5;
    private const uint _animLength = 50;
    async void OnPanGestureUpdated(object sender, PanUpdatedEventArgs e)
    {
        if (Thumb == null | TrackBar == null)
            return;

        switch (e.StatusType)
        {
            case GestureStatus.Started:
                await TrackBar.FadeTo(_fadeEffect, _animLength);
                break;

            case GestureStatus.Running:
                // Translate and ensure we don't pan beyond the wrapped user interface element bounds.
                var x = Math.Max(0, e.TotalX);
                if (x > (Width - Thumb.Width))
                    x = (Width - Thumb.Width);

                if (e.TotalX < Thumb.TranslationX)
                    return;
                Thumb.TranslationX = x;
                break;

            case GestureStatus.Completed:
                var posX = Thumb.TranslationX;

                // Reset translation applied during the pan (snap effect)
                await TrackBar.FadeTo(1, _animLength);
                await Thumb.TranslateTo(0, 0, _animLength * 2, Easing.CubicIn);

                if (posX >= (Width - Thumb.Width - 10/* keep some margin for error*/))
                    SlideCompleted?.Invoke(this, EventArgs.Empty);
                break;
        }
    }

    void OnSizeChanged(object sender, EventArgs e)
    {
        if (Width == 0 || Height == 0)
            return;
        if (Thumb == null || TrackBar == null)
            return;


        Children.Clear();

        SetLayoutFlags(TrackBar, AbsoluteLayoutFlags.SizeProportional);
        SetLayoutBounds(TrackBar, new Rectangle(0, 0, 1, 1));
        Children.Add(TrackBar);

        SetLayoutFlags(Thumb, AbsoluteLayoutFlags.None);
        SetLayoutBounds(Thumb, new Rectangle(0, 0, this.Width/5, this.Height));
        Children.Add(Thumb);

        SetLayoutFlags(_gestureListener, AbsoluteLayoutFlags.SizeProportional);
        SetLayoutBounds(_gestureListener, new Rectangle(0, 0, 1, 1));
        Children.Add(_gestureListener);
    }
}

示例用法:

<StackLayout Margin="40">
    <local:SlideToActView HeightRequest="50" SlideCompleted="Handle_SlideCompleted">
        <local:SlideToActView.Thumb>
            <Frame CornerRadius="10" HasShadow="false" BackgroundColor="Silver" Padding="0">
                <Image Source="icon.png" HorizontalOptions="Center" VerticalOptions="Center" HeightRequest="40" WidthRequest="40" />
            </Frame>
        </local:SlideToActView.Thumb>

        <local:SlideToActView.TrackBar>
            <Frame CornerRadius="10" HasShadow="false" BackgroundColor="Gray" Padding="0">
                <Label Text="Slide 'x' to cancel" HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand" />
            </Frame>
        </local:SlideToActView.TrackBar>
    </local:SlideToActView>
    <Label x:Name="MessageLbl" FontAttributes="Bold" TextColor="Green" />
</StackLayout>

代码隐藏

void Handle_SlideCompleted(object sender, System.EventArgs e)
{
    MessageLbl.Text = "Success!!";
}

更新:08/30

正如@morten-j-petersen 想要支持类似填充条的实现；增加了对此的支持。

更新控制代码

public class SlideToActView : AbsoluteLayout
{
    public static readonly BindableProperty ThumbProperty =
        BindableProperty.Create(
            "Thumb", typeof(View), typeof(SlideToActView),
            defaultValue: default(View));

    public View Thumb
    {
        get { return (View)GetValue(ThumbProperty); }
        set { SetValue(ThumbProperty, value); }
    }

    public static readonly BindableProperty TrackBarProperty =
        BindableProperty.Create(
            "TrackBar", typeof(View), typeof(SlideToActView),
            defaultValue: default(View));

    public View TrackBar
    {
        get { return (View)GetValue(TrackBarProperty); }
        set { SetValue(TrackBarProperty, value); }
    }

    public static readonly BindableProperty FillBarProperty =
        BindableProperty.Create(
            "FillBar", typeof(View), typeof(SlideToActView),
            defaultValue: default(View));

    public View FillBar
    {
        get { return (View)GetValue(FillBarProperty); }
        set { SetValue(FillBarProperty, value); }
    }

    private PanGestureRecognizer _panGesture = new PanGestureRecognizer();
    private View _gestureListener;
    public SlideToActView()
    {
        _panGesture.PanUpdated += OnPanGestureUpdated;
        SizeChanged += OnSizeChanged;

        _gestureListener = new ContentView { BackgroundColor = Color.White, Opacity = 0.05 };
        _gestureListener.GestureRecognizers.Add(_panGesture);
    }

    public event EventHandler SlideCompleted;

    private const double _fadeEffect = 0.5;
    private const uint _animLength = 50;
    async void OnPanGestureUpdated(object sender, PanUpdatedEventArgs e)
    {
        if (Thumb == null || TrackBar == null || FillBar == null)
            return;

        switch (e.StatusType)
        {
            case GestureStatus.Started:
                await TrackBar.FadeTo(_fadeEffect, _animLength);
                break;

            case GestureStatus.Running:
                // Translate and ensure we don't pan beyond the wrapped user interface element bounds.
                var x = Math.Max(0, e.TotalX);
                if (x > (Width - Thumb.Width))
                    x = (Width - Thumb.Width);

                //Uncomment this if you want only forward dragging.
                //if (e.TotalX < Thumb.TranslationX)
                //    return;
                Thumb.TranslationX = x;
                SetLayoutBounds(FillBar, new Rectangle(0, 0, x + Thumb.Width / 2, this.Height));
                break;

            case GestureStatus.Completed:
                var posX = Thumb.TranslationX;
                SetLayoutBounds(FillBar, new Rectangle(0, 0, 0, this.Height));

                // Reset translation applied during the pan
                await Task.WhenAll(new Task[]{
                    TrackBar.FadeTo(1, _animLength),
                    Thumb.TranslateTo(0, 0, _animLength * 2, Easing.CubicIn),
                });

                if (posX >= (Width - Thumb.Width - 10/* keep some margin for error*/))
                    SlideCompleted?.Invoke(this, EventArgs.Empty);
                break;
        }
    }

    void OnSizeChanged(object sender, EventArgs e)
    {
        if (Width == 0 || Height == 0)
            return;
        if (Thumb == null || TrackBar == null || FillBar == null)
            return;


        Children.Clear();

        SetLayoutFlags(TrackBar, AbsoluteLayoutFlags.SizeProportional);
        SetLayoutBounds(TrackBar, new Rectangle(0, 0, 1, 1));
        Children.Add(TrackBar);

        SetLayoutFlags(FillBar, AbsoluteLayoutFlags.None);
        SetLayoutBounds(FillBar, new Rectangle(0, 0, 0, this.Height));
        Children.Add(FillBar);

        SetLayoutFlags(Thumb, AbsoluteLayoutFlags.None);
        SetLayoutBounds(Thumb, new Rectangle(0, 0, this.Width/5, this.Height));
        Children.Add(Thumb);

        SetLayoutFlags(_gestureListener, AbsoluteLayoutFlags.SizeProportional);
        SetLayoutBounds(_gestureListener, new Rectangle(0, 0, 1, 1));
        Children.Add(_gestureListener);


    }
}

XAML 用法

<StackLayout Margin="40">
    <local:SlideToActView HeightRequest="50" SlideCompleted="Handle_SlideCompleted">
        <local:SlideToActView.Thumb>
            <Frame CornerRadius="10" HasShadow="false" BackgroundColor="Silver" Padding="0">
                <Image Source="icon.png" HorizontalOptions="Center" VerticalOptions="Center" HeightRequest="40" WidthRequest="40" />
            </Frame>
        </local:SlideToActView.Thumb>

        <local:SlideToActView.TrackBar>
            <Frame CornerRadius="10" HasShadow="false" BackgroundColor="Gray" Padding="0">
                <Label Text="Slide 'x' to cancel" HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand" />
            </Frame>
        </local:SlideToActView.TrackBar>

        <local:SlideToActView.FillBar>
            <Frame CornerRadius="10" HasShadow="false" BackgroundColor="Red" Padding="0" />
        </local:SlideToActView.FillBar>
    </local:SlideToActView>
    <Label x:Name="MessageLbl" FontAttributes="Bold" TextColor="Green" />
</StackLayout>