Xamarin 窗体 DisplayAlert 按钮 TextColor

Question

如何更改 Xamarin Forms DisplayAlert 对话框上的按钮文本颜色？

Answer 1

可以在custom renderers 的帮助下为每个平台更改颜色。 您可以在自定义渲染器中访问本机 api。 但需要确定是需要的，因为不推荐（对于 iOS 肯定）。

The UIAlertView class is intended to be used as-is and does not support subclassing. The view hierarchy for this class is private and must not be modified.

iOS 相关主题here。

Answer 2

FWIW，我选择在 XAML 中创建一个新的 ContentPage 并使用 Navigation.PushModalAsync 显示它。就我而言，这是模拟警报并保持对所有样式的控制的最简单方法。

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="YourNamespace.AlertPage"
             BackgroundColor="DarkGray"
             Padding="40">
    <ContentPage.Content>
        <StackLayout BackgroundColor="White" Padding="10">
            <Label x:Name="lblTitle" FontAttributes="Bold" FontSize="Large" Text="Title" HorizontalOptions="Center"></Label>
            <BoxView HeightRequest="1" BackgroundColor="DarkGray"></BoxView>
            <ScrollView Orientation="Vertical" VerticalOptions="FillAndExpand">
                <Label x:Name="lblText" FontSize="Medium"></Label>
            </ScrollView>
            <BoxView HeightRequest="1" BackgroundColor="DarkGray"></BoxView>
            <StackLayout Orientation="Horizontal">
                <Button x:Name="btn1" Text="Button 1" HorizontalOptions="CenterAndExpand"></Button>
                <Button x:Name="btn2" Text="Button 2" HorizontalOptions="CenterAndExpand"></Button>
            </StackLayout>
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

C#：

public partial class AlertPage : ContentPage
{
    public Label LblTitle
    {
        get
        {
            return lblTitle;
        }
    }

    public Label LblText
    {
        get
        {
            return lblText;
        }
    }

    public Button Button1
    {
        get
        {
            return btn1;
        }
    }

    public Button Button2
    {
        get
        {
            return btn2;
        }
    }

    public AlertPage()
    {
        InitializeComponent();
    }
}

实施：

var ap = new AlertPage();
ap.LblTitle.Text = "Instructions";
ap.LblText.Text = "The text to display!";
ap.Button1.Text = "Done";
ap.Button1.Clicked += async (s, a) =>
{
    await Navigation.PopModalAsync();
};
ap.Button2.IsVisible = false;
await Navigation.PushModalAsync(ap);

截图：

Answer 3

我已经创建了自定义显示警报，您可以使用任务回调 TaskCompletionSource 作为 xamarin build DisplayAlert from it

    public async Task<bool> ShowDialogAsync(string title, string message, string acceptMessage, string cancelMessage)
                {
                    Grid ShowDialogMessage = null;
                    Grid CurrentPageGrid = (App.Instance.CurrentPage as ContentPage).Content as Grid;
                    TaskCompletionSource<bool> result = new TaskCompletionSource<bool>();
                    try
                    {
                        ShowDialogMessage = GenericView.CustomDisplayAlert(message, CurrentPageGrid.RowDefinitions.Count, CurrentPageGrid.ColumnDefinitions.Count, () =>
                        {
         //here you can add your implementation   
                            CurrentPageGrid.Children.Remove(ShowDialogMessage);

  result.SetResult(true);

                        },
                        () =>
                        {
         //here you can add your implementation      
                            CurrentPageGrid.Children.Remove(ShowDialogMessage);
                            result.SetResult(false);
                        }, title, acceptMessage, cancelMessage);

                        CurrentPageGrid.Children.Add(ShowDialogMessage);
                        return await result.Task;
                    }
                    catch (Exception ex)
                    {
                        return await App.Current.MainPage.DisplayAlert(title, message, acceptMessage, cancelMessage);
        #if DEBUG
                        throw ex;
        #endif
                    }

                }

在我的方法中，我添加了实现回调的操作，方法签名您可以添加自己的设计

 public static Grid CustomDisplayAlert(string message, int rows, int columns, Action acceptAction, Action cancelAction, string title = "", string acceptMessage = "", string cancelMessage = "")
        {           
             Grid overlay = new Grid
            {
                BackgroundColor = Color.FromRgba(0, 0, 0, 190),
                RowDefinitions = new RowDefinitionCollection { new RowDefinition { Height = GridLength.Star }, new RowDefinition { Height = GridLength.Auto }, new RowDefinition { Height = GridLength.Star } }
            };

                Grid.SetRowSpan(overlay, rows);

                Grid.SetColumnSpan(overlay, columns);


            Grid bodyView = new Grid();


            StackLayout stackMainView = new StackLayout
            {
                Margin = new Thickness(20)
            };
            StackLayout stackButtonsView = new StackLayout
            {
                Orientation=StackOrientation.Horizontal 
            };
            RoundedBox bgOverlay = new RoundedBox
            {
                CornerRadius = 4,
                HorizontalOptions = LayoutOptions.FillAndExpand,
                VerticalOptions = LayoutOptions.FillAndExpand,
                BackgroundColor = Color.White
            };

            bodyView.Children.Add(bgOverlay);

            StackLayout elementsContainer = new StackLayout { Margin = new Thickness(10) };

            IconicLabel itemDescription = new IconicLabel { MoreReadable = true, Text = message, StyleId = "Myriad-Pro-L", HorizontalTextAlignment = TextAlignment.Center, HorizontalOptions = LayoutOptions.FillAndExpand, TextColor = (Color)(App.Current.Resources["OptioDark"]), FontSize = 18, Margin = new Thickness(15) };
            IconicLabel titleView = new IconicLabel { FontAttributes = FontAttributes.Bold, MoreReadable = true, Text = title, StyleId = "Myriad-Pro-L", HorizontalTextAlignment = TextAlignment.Center, HorizontalOptions = LayoutOptions.FillAndExpand, TextColor = (Color)(App.Current.Resources["OptioDark"]), FontSize = 22, Margin = new Thickness(15) };

            if (titleView.Text.Length != 0)
                elementsContainer.Children.Add(titleView);
            elementsContainer.Children.Add(itemDescription);


            bodyView.Children.Add(elementsContainer);

            IconicButton acceptBtn = new IconicButton
            {
                HeightRequest = 40,
                HorizontalOptions = LayoutOptions.FillAndExpand,
                VerticalOptions = LayoutOptions.FillAndExpand,
                BackgroundColor = Color.White,
                Text = acceptMessage,
                TextColor = (Color)(App.Current.Resources["OptioDark"])
            };
            IconicButton cancelBtn = new IconicButton
            {
                HeightRequest = 40,
                HorizontalOptions = LayoutOptions.FillAndExpand,
                VerticalOptions = LayoutOptions.FillAndExpand,
                BackgroundColor = Color.White,
                Text = cancelMessage,
                TextColor = (Color)(App.Current.Resources["OptioDark"])
            };
            acceptBtn.Clicked += (sender, e) =>
            {
                acceptAction?.Invoke();
            };
            cancelBtn.Clicked += (sender, e) =>
            {
                cancelAction?.Invoke();
            };

            stackButtonsView.Children.Add(acceptBtn);
            stackButtonsView.Children.Add(cancelBtn);

            stackMainView.Children.Add(bodyView);

            stackMainView.Children.Add(stackButtonsView);
            overlay.Children.Add(stackMainView, 0, 1);
            return overlay;

        }