.NET Maui 7中如何修改DisplayAlert弹窗按钮文字颜色？

针对你遇到的DisplayAlert按钮文字为白色的问题，提供两种可行的解决方案：

方案一：通过自定义Handler替换原生弹窗逻辑 #

这种方式无需额外依赖，直接针对Android和iOS平台修改原生Alert控件的按钮文字颜色：

Android平台实现 #

1. 在MauiProgram.cs中注册自定义PageHandler：

builder.ConfigureMauiHandlers(handlers =>
{
#if ANDROID
    handlers.AddHandler<Microsoft.Maui.Controls.Page, CustomPageHandler>();
#endif
});

2. 创建CustomPageHandler类，重写DisplayAlert逻辑：

#if ANDROID
using Android.App;
using Android.Content;
using Microsoft.Maui.Handlers;

public class CustomPageHandler : PageHandler
{
    protected override void ConnectHandler(Microsoft.Maui.Controls.Page view)
    {
        base.ConnectHandler(view);
        // 替换默认的DisplayAlert实现
        view.DisplayAlert = async (title, message, accept, cancel) =>
        {
            var alertDialog = new AlertDialog.Builder(Context)
                .SetTitle(title)
                .SetMessage(message);

            alertDialog.SetPositiveButton(accept, (sender, args) => { });
            if (!string.IsNullOrEmpty(cancel))
            {
                alertDialog.SetNegativeButton(cancel, (sender, args) => { });
            }

            var dialog = alertDialog.Create();
            dialog.Show();

            // 设置按钮文字颜色（这里用红色和蓝色示例，可替换为你需要的颜色值）
            dialog.GetButton((int)DialogButtonType.Positive).SetTextColor(Android.Graphics.Color.ParseColor("#FF0000"));
            if (!string.IsNullOrEmpty(cancel))
            {
                dialog.GetButton((int)DialogButtonType.Negative).SetTextColor(Android.Graphics.Color.ParseColor("#0000FF"));
            }

            var tcs = new TaskCompletionSource<bool>();
            dialog.DismissEvent += (s, e) =>
            {
                tcs.SetResult(dialog.GetButton((int)DialogButtonType.Positive).IsPressed);
            };

            return await tcs.Task;
        };
    }
}
#endif

iOS平台实现 #

1. 同样在MauiProgram.cs中注册自定义PageHandler：

builder.ConfigureMauiHandlers(handlers =>
{
#if IOS
    handlers.AddHandler<Microsoft.Maui.Controls.Page, CustomPageHandler>();
#endif
});

2. 创建iOS版本的CustomPageHandler：

#if IOS
using UIKit;
using Microsoft.Maui.Handlers;

public class CustomPageHandler : PageHandler
{
    protected override void ConnectHandler(Microsoft.Maui.Controls.Page view)
    {
        base.ConnectHandler(view);
        view.DisplayAlert = async (title, message, accept, cancel) =>
        {
            var alertController = UIAlertController.Create(title, message, UIAlertControllerStyle.Alert);

            alertController.AddAction(UIAlertAction.Create(accept, UIAlertActionStyle.Default, action => { }));
            if (!string.IsNullOrEmpty(cancel))
            {
                alertController.AddAction(UIAlertAction.Create(cancel, UIAlertActionStyle.Cancel, action => { }));
            }

            // 设置按钮文字颜色（示例为红色和蓝色）
            alertController.Actions[0].SetValueForKey(UIKit.UIColor.Red, new Foundation.NSString("titleTextColor"));
            if (alertController.Actions.Count > 1)
            {
                alertController.Actions[1].SetValueForKey(UIKit.UIColor.Blue, new Foundation.NSString("titleTextColor"));
            }

            var window = UIApplication.SharedApplication.KeyWindow;
            var viewController = window.RootViewController;
            while (viewController.PresentedViewController != null)
            {
                viewController = viewController.PresentedViewController;
            }

            var tcs = new TaskCompletionSource<bool>();
            alertController.Dismissed += (s, e) =>
            {
                tcs.SetResult(alertController.Actions[0].Clicked);
            };

            viewController.PresentViewController(alertController, true, null);
            return await tcs.Task;
        };
    }
}
#endif

方案二：使用自定义弹窗替代DisplayAlert #

如果你需要跨平台统一的样式，推荐使用CommunityToolkit.Maui的Popup控件，完全自定义弹窗样式：

1. 安装NuGet包：

Install-Package CommunityToolkit.Maui

2. 在MauiProgram.cs中注册工具包：

builder.UseMauiApp<App>().UseMauiCommunityToolkit();

3. 创建自定义弹窗页面CustomAlertPopup.xaml：

<?xml version="1.0" encoding="utf-8" ?>
<toolkit:Popup xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
             x:Class="YourAppNamespace.CustomAlertPopup"
             Size="300,200">
    <VerticalStackLayout Padding="20" Spacing="15" BackgroundColor="White">
        <Label Text="{Binding Title}" FontSize="Headline" HorizontalOptions="Center" TextColor="Black"/>
        <Label Text="{Binding Message}" FontSize="Body" HorizontalOptions="Center" TextColor="Gray"/>
        <HorizontalStackLayout Spacing="10" HorizontalOptions="End">
            <Button Text="{Binding CancelText}" TextColor="Blue" BackgroundColor="Transparent" Clicked="CancelButton_Clicked"/>
            <Button Text="{Binding AcceptText}" TextColor="Red" BackgroundColor="Transparent" Clicked="AcceptButton_Clicked"/>
        </HorizontalStackLayout>
    </VerticalStackLayout>
</toolkit:Popup>

4. 弹窗后台代码CustomAlertPopup.xaml.cs：

using CommunityToolkit.Maui.Views;

namespace YourAppNamespace;

public partial class CustomAlertPopup : Popup
{
    public bool Result { get; private set; }

    public CustomAlertPopup(string title, string message, string acceptText, string cancelText)
    {
        InitializeComponent();
        BindingContext = new { Title = title, Message = message, AcceptText = acceptText, CancelText = cancelText };
    }

    private void AcceptButton_Clicked(object sender, EventArgs e)
    {
        Result = true;
        Close();
    }

    private void CancelButton_Clicked(object sender, EventArgs e)
    {
        Result = false;
        Close();
    }
}

5. 调用自定义弹窗：

var popup = new CustomAlertPopup("Sure ?", "Are you sure ?", "Yes", "No");
await this.ShowPopupAsync(popup);
bool answer = popup.Result;

内容的提问来源于stack exchange，提问作者Thomas Carlton