c# - 单击按钮上的 Xamarin.Forms 动画(Flash 背景)

Question

我想在我的表单上实现拨号盘。现在，在我的 XAML 中我正在测试一个按钮:XAML

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
         x:Class="MyXFDemo001.Views.NewItemPage"
         Title="New Item">
<ContentPage.ToolbarItems>
    <ToolbarItem Text="Save" Clicked="Save_Clicked" />
</ContentPage.ToolbarItems>
<ContentPage.Content>
    <StackLayout Spacing="20" Padding="15">
        <Button
            x:Name="buttonSelectContact"
            Clicked="buttonSelectContact_Clicked"
            Text="CLICK" BackgroundColor="#0080ff" />
    </StackLayout>
</ContentPage.Content>

在我的代码后面，我有一个方法buttonSelectContact_Clicked:

private async void buttonSelectContact_Clicked(object sender, EventArgs e)
{
    Button btn = (Button)sender;
    btn.BackgroundColor = Color.FromHex("#22ac38");
    await Task.Delay(500);
    btn.BackgroundColor = Color.FromHex("#0080ff");
}

它可以工作，但并不像我想要的那样顺利。你能建议我添加动画而不是这个BackgroundColor吗？

Answer 1

我想更好的选择是创建一个可重用的功能来做到这一点。您可以利用 xamarin.forms 的动画资源.

例如，您可以创建一个扩展方法，为您提供一种在任何地方重复使用的好用且简单的方法，例如 FadeTo 或 TranslateTo...

这非常简单，除了在这种特殊情况下平滑改变颜色的逻辑之外。这是代码:

public static class AnimationExtensions
{
    public static Task<bool> ChangeBackgroundColorTo(this Button self, Color newColor, uint length = 250, Easing easing = null)
    {
        Task<bool> ret = new Task<bool>(() => false);

        if (!self.AnimationIsRunning(nameof(ChangeBackgroundColorTo)))
        {
            Color fromColor = self.BackgroundColor;

            try
            {
                Func<double, Color> transform = (t) =>
                  Color.FromRgba(fromColor.R + t * (newColor.R - fromColor.R),
                                 fromColor.G + t * (newColor.G - fromColor.G),
                                 fromColor.B + t * (newColor.B - fromColor.B),
                                 fromColor.A + t * (newColor.A - fromColor.A));

                ret = TransmuteColorAnimation(self, nameof(ChangeBackgroundColorTo), transform, length, easing);
            }
            catch (Exception ex)
            {
                // to supress animation overlapping errors 
                self.BackgroundColor = fromColor;
            }
        }

        return ret;
    }

    private static Task<bool> TransmuteColorAnimation(Button button, string name, Func<double, Color> transform, uint length, Easing easing)
    {
        easing = easing ?? Easing.Linear;
        var taskCompletionSource = new TaskCompletionSource<bool>();

        button.Animate(name, transform, (color) => { button.BackgroundColor = color; }, 16, length, easing, (v, c) => taskCompletionSource.SetResult(c));
        return taskCompletionSource.Task;
    }
}

导入此类(通过 using namespace 引用)，您将能够像下面一样使用它。

声明 XAML 按钮:

<Button Text="Nice button ;)"
        BackgroundColor="Gray"
        x:Name="btnTeste"
        Clicked="btnTest_Click"/>

在代码隐藏中处理点击:

private async void btnTest_Click(object sender, EventArgs args)
{
    #region You will not need this block, it is just to choose a random color for change to
    var colors = new[] { Color.Red, Color.Pink, Color.Silver, Color.Yellow, Color.Black, Color.Green };
    var rnd = new Random();

    var actualColor = btnTeste.BackgroundColor;
    var randomColor = colors.Where(c => c != actualColor).ToArray()[rnd.Next(0, colors.Length - 2)];
    #endregion

    // Here is the effective use of the smooth background color change animation
    await btnTeste.ChangeBackgroundColorTo(randomColor, 150, Easing.CubicOut);
    await btnTeste.ChangeBackgroundColorTo(actualColor, 100, Easing.SinOut);
}

编辑:

这是结果(gif 显示了单击和双击，因此您可以看到很多平滑的更改):