.NET MAUI 8.0连接条码阅读器（物理键盘）后如何调出虚拟键盘？

针对蓝牙条码阅读器被识别为物理键盘导致虚拟键盘无法弹出的问题，可通过自定义平台Handler的方式强制触发虚拟键盘，以下是各平台的具体实现：

1. 共享项目创建自定义Entry #

先在共享项目中定义一个继承自Entry的自定义控件，用于统一各平台的处理逻辑：

namespace YourAppNamespace;

public class ForceVirtualKeyboardEntry : Entry
{
}

2. Android平台实现 #

Android默认会在连接物理键盘时隐藏虚拟键盘，通过自定义EntryHandler强制开启软键盘：

using Android.Content;
using Android.Views.InputMethods;
using Microsoft.Maui.Platform;

namespace YourAppNamespace.Platforms.Android;

public class ForceVirtualKeyboardEntryHandler : EntryHandler
{
    protected override void ConnectHandler(MauiTextView platformView)
    {
        base.ConnectHandler(platformView);
        // 设置控件获取焦点时显示软键盘
        platformView.ShowSoftInputOnFocus = true;
    }

    public static void MapForceVirtualKeyboard(IEntryHandler handler, IEntry entry)
    {
        if (handler.PlatformView is MauiTextView textView && handler.Context != null)
        {
            var inputManager = (InputMethodManager)handler.Context.GetSystemService(Context.InputMethodService);
            // 强制弹出软键盘
            inputManager.ShowSoftInput(textView, ShowFlags.Forced);
            inputManager.ToggleSoftInput(ShowFlags.Forced, HideSoftInputFlags.ImplicitOnly);
        }
    }
}

在MauiProgram.cs中注册Handler：

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

3. iOS平台实现 #

iOS外接键盘连接后会自动隐藏虚拟键盘，通过自定义Handler强制唤起：

using UIKit;
using Microsoft.Maui.Platform;

namespace YourAppNamespace.Platforms.iOS;

public class ForceVirtualKeyboardEntryHandler : EntryHandler
{
    protected override void ConnectHandler(UITextField platformView)
    {
        base.ConnectHandler(platformView);
        // 移除输入助理栏，避免干扰虚拟键盘弹出
        platformView.InputAssistantItem.LeadingBarButtonGroups = null;
        platformView.InputAssistantItem.TrailingBarButtonGroups = null;
        
        // 强制控件获取焦点并弹出虚拟键盘
        platformView.BecomeFirstResponder();
        platformView.InputViewController?.BecomeFirstResponder();
    }
}

在MauiProgram.cs中注册Handler：

builder.ConfigureMauiHandlers(handlers =>
{
#if IOS
    handlers.AddHandler<ForceVirtualKeyboardEntry, ForceVirtualKeyboardEntryHandler>();
#endif
});

4. Windows平台实现 #

Windows上通过InputPane强制调出触摸键盘：

using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Input;
using Microsoft.Maui.Platform;

namespace YourAppNamespace.Platforms.Windows;

public class ForceVirtualKeyboardEntryHandler : EntryHandler
{
    protected override void ConnectHandler(TextBox platformView)
    {
        base.ConnectHandler(platformView);
        // 绑定焦点事件，触发时弹出触摸键盘
        platformView.GotFocus += OnPlatformViewGotFocus;
    }

    private void OnPlatformViewGotFocus(object sender, Microsoft.UI.Xaml.RoutedEventArgs e)
    {
        var inputPane = InputPane.GetForCurrentView();
        inputPane.TryShow();
    }

    protected override void DisconnectHandler(TextBox platformView)
    {
        platformView.GotFocus -= OnPlatformViewGotFocus;
        base.DisconnectHandler(platformView);
    }
}

在MauiProgram.cs中注册Handler：

builder.ConfigureMauiHandlers(handlers =>
{
#if WINDOWS
    handlers.AddHandler<ForceVirtualKeyboardEntry, ForceVirtualKeyboardEntryHandler>();
#endif
});

5. 在XAML中使用 #

替换原有的Entry为自定义控件即可：

<local:ForceVirtualKeyboardEntry Placeholder="输入商品名称搜索" />

注意事项 #

• Android端需确保控件已获取焦点后再调用软键盘显示方法，可结合Focused事件调整逻辑；
• iOS 14+可额外重写UITextField的ShouldShowVirtualKeyboard委托增强兼容性；
• Windows端InputPane.TryShow()仅在触摸设备或开启触摸键盘模式时生效。

内容的提问来源于stack exchange，提问作者Miguel Pires