在.NET MAUI中用自定义Entry Handler实现自定义键盘视图的求助

步骤1：创建跨平台自定义Entry控件 #

在共享项目中定义继承自Entry的自定义控件，用于绑定平台Handler：

namespace YourApp.Controls;

public class CustomKeyboardEntry : Entry
{
    // 可根据需求添加自定义绑定属性，比如键盘类型、是否启用自定义键盘等
}

步骤2：实现Android平台自定义Handler #

在Android平台项目中创建Handler，替代默认EntryHandler行为，禁用系统键盘并绑定自定义键盘逻辑：

using Android.Content;
using Android.Views.InputMethods;
using Android.Widget;
using YourApp.Controls;
using Microsoft.Maui.Handlers;

namespace YourApp.Platforms.Android.Handlers;

public class CustomKeyboardEntryHandler : EntryHandler
{
    protected override void ConnectHandler(EditText platformView)
    {
        base.ConnectHandler(platformView);
        
        // 禁用系统自动弹出键盘
        platformView.ShowSoftInputOnFocus = false;
        // 绑定焦点事件，控制自定义键盘显隐
        platformView.FocusChange += OnFocusChanged;
    }

    protected override void DisconnectHandler(EditText platformView)
    {
        platformView.FocusChange -= OnFocusChanged;
        base.DisconnectHandler(platformView);
    }

    private void OnFocusChanged(object sender, Android.Views.View.FocusChangeEventArgs e)
    {
        if (e.HasFocus)
        {
            ShowCustomKeyboard();
        }
        else
        {
            HideCustomKeyboard();
        }
    }

    private void ShowCustomKeyboard()
    {
        // 实例化自定义键盘视图
        var customKeyboard = new CustomKeyboard(Context);
        
        // 绑定按键点击事件，向Entry输入内容
        customKeyboard.KeyPressed += keyValue =>
        {
            if (keyValue == "←")
            {
                // 处理删除键逻辑
                if (!string.IsNullOrEmpty(VirtualView.Text))
                {
                    VirtualView.Text = VirtualView.Text.Substring(0, VirtualView.Text.Length - 1);
                    VirtualView.CursorPosition = VirtualView.Text.Length;
                }
            }
            else if (keyValue == "Clear")
            {
                VirtualView.Text = string.Empty;
            }
            else
            {
                // 处理普通输入键
                VirtualView.Text += keyValue;
                VirtualView.CursorPosition = VirtualView.Text.Length;
            }
        };

        // 替换系统键盘显示逻辑
        var imm = (InputMethodManager)Context.GetSystemService(Context.InputMethodService);
        imm.ShowSoftInput(VirtualView, ShowFlags.Forced);
        
        // 将自定义键盘添加到当前页面底部
        if (MauiContext?.View is Android.Views.View parentView)
        {
            var layoutParams = new LayoutParams(LayoutParams.MatchParent, LayoutParams.WrapContent);
            layoutParams.Gravity = GravityFlags.Bottom;
            parentView.AddView(customKeyboard, layoutParams);
        }
    }

    private void HideCustomKeyboard()
    {
        var imm = (InputMethodManager)Context.GetSystemService(Context.InputMethodService);
        imm.HideSoftInputFromWindow(PlatformView.WindowToken, HideSoftInputFlags.None);
        
        // 移除自定义键盘视图
        if (MauiContext?.View is Android.Views.View parentView)
        {
            for (int i = 0; i < parentView.ChildCount; i++)
            {
                if (parentView.GetChildAt(i) is CustomKeyboard keyboard)
                {
                    parentView.RemoveView(keyboard);
                    break;
                }
            }
        }
    }
}

步骤3：实现Android自定义键盘视图 #

创建自定义键盘的Android原生视图，定义按键布局和点击逻辑：

using Android.Content;
using Android.Views;
using Android.Widget;

namespace YourApp.Platforms.Android;

public class CustomKeyboard : LinearLayout
{
    public event Action<string>? KeyPressed;

    public CustomKeyboard(Context context) : base(context)
    {
        Orientation = Orientation.Vertical;
        LayoutParameters = new LayoutParams(LayoutParams.MatchParent, LayoutParams.WrapContent);
        SetBackgroundColor(Android.Graphics.Color.LightGray);
        
        // 构建键盘行
        AddKeyboardRow(new[] { "1", "2", "3", "←" });
        AddKeyboardRow(new[] { "4", "5", "6", "Clear" });
        AddKeyboardRow(new[] { "7", "8", "9", "Done" });
        AddKeyboardRow(new[] { "0", ".", "@" });
    }

    private void AddKeyboardRow(string[] keys)
    {
        var row = new LinearLayout(Context)
        {
            Orientation = Orientation.Horizontal,
            LayoutParameters = new LayoutParams(LayoutParams.MatchParent, LayoutParams.WrapContent)
        };

        foreach (var key in keys)
        {
            var button = new Button(Context)
            {
                Text = key,
                LayoutParameters = new LayoutParams(0, LayoutParams.MatchParent, 1f),
                Padding = new Padding(10, 15, 10, 15)
            };

            button.Click += (s, e) =>
            {
                if (key == "Done")
                {
                    // 处理完成逻辑：关闭键盘并失去焦点
                    KeyPressed?.Invoke("");
                    ClearFocus();
                }
                else
                {
                    KeyPressed?.Invoke(key);
                }
            };

            row.AddView(button);
        }

        AddView(row);
    }
}

步骤4：注册Handler #

在MauiProgram.cs中注册自定义Handler：

builder.ConfigureMauiHandlers(handlers =>
{
#if ANDROID
    handlers.AddHandler<CustomKeyboardEntry, CustomKeyboardEntryHandler>();
#endif
});

步骤5：在XAML中使用自定义控件 #

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:controls="clr-namespace:YourApp.Controls"
             x:Class="YourApp.MainPage">

    <StackLayout Padding="20">
        <controls:CustomKeyboardEntry Placeholder="点击输入内容" />
    </StackLayout>
</ContentPage>

内容的提问来源于stack exchange，提问作者Amandeep