MAUI自定义Entry/Editor在Android11/13下文本及占位符异常问题

一、Android平台特定版本UI异常 #

MAUI应用中自定义Entry和Editor的占位符颜色与文本颜色无法正常显示，UI呈现空白状态。该问题仅出现在Android 11和Android 13系统中，Android 10与Android 12可正常运行。

自定义Entry渲染器代码 #

public class CustomEntryRenderer : EntryRenderer
{
    public CustomEntryRenderer(Context context) : base(context)
    {
    }

    protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
    {
        base.OnElementChanged(e);

        if (Control != null)
        {
            GradientDrawable gd = new GradientDrawable();
            gd.SetColor(global::Android.Graphics.Color.Transparent);
            this.Control.Background = gd;
            this.Control.SetRawInputType(InputTypes.TextFlagNoSuggestions);
        }
    }
}

自定义Editor渲染器代码 #

public class CustomNoUnderLineEditorRenderer : EditorRenderer
{
    public CustomNoUnderLineEditorRenderer(Context context) : base(context)
    {
    }

    protected override void OnElementChanged(ElementChangedEventArgs<Editor> e)
    {
        base.OnElementChanged(e);

        if (Control != null)
        {
            GradientDrawable gd = new GradientDrawable();
            gd.SetColor(global::Android.Graphics.Color.Transparent);
            this.Control.SetBackgroundDrawable(gd);
            this.Control.SetRawInputType(InputTypes.TextFlagNoSuggestions);
            Control.SetHintTextColor(ColorStateList.ValueOf(global::Android.Graphics.Color.Gray));
        }
    }
}

XAML布局代码 #

<Frame 
     x:Name="titleentry_frame"
     Margin="0,5,0,5"
     Style="{StaticResource CreateRequest_Editor_FrameStyle}">

    <renderer:CustomEntry
     x:Name="title_entry"
     Keyboard="Default"
     Placeholder="Enter title"
     Style="{StaticResource CreateRequest_EntryStyle}"/>
</Frame>

<Frame 
     x:Name="requesteditor_frame"
     Margin="0,11,0,11"
     Style="{StaticResource CreateRequest_Editor_FrameStyle}">

    <renderer:CustomNoUnderLineEditor
        x:Name="description_editor"
        AutoSize="TextChanges"
        Placeholder="Enter description"
        Style="{StaticResource CreateRequest_EditorStyle}">
    </renderer:CustomNoUnderLineEditor>
</Frame>

二、iOS平台：渲染器迁移至Handler的需求（2023-11-02更新） #

以下为原iOS平台自定义Entry和Editor的渲染器代码，需要迁移至Handler实现，求示例代码：

iOS自定义Entry渲染器 #

public class CustomEntryRenderer : EntryRenderer
{
    protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
    {
        base.OnElementChanged(e);

        if (Control != null)
        {
            Control.BorderStyle = UITextBorderStyle.None;
        }
    }
}

iOS自定义Editor渲染器 #

public class CustomEditorRenderer : EditorRenderer
{
    public CustomEditorRenderer()
    {
        UIKeyboard.Notifications.ObserveWillShow((sender, args) =>
        {
            if (Element != null)
            {
                Element.Margin = new Thickness(0, 0, 0, args.FrameEnd.Height);
            }
        });

        UIKeyboard.Notifications.ObserveWillHide((sender, args) =>
        {
            if (Element != null)
            {
                Element.Margin = new Thickness(0);
            }
        });
    }
    
    protected override void OnElementChanged(ElementChangedEventArgs<Editor> e)
    {
        base.OnElementChanged(e);

        if (Control != null)
        {
            Control.BorderStyle = UITextBorderStyle.None;
            Control.Layer.CornerRadius = 10;
            Control.TextColor = UIColor.Black;
        }
    }
}

三、iOS迁移后报错及残留问题（2023-11-03更新） #

添加iOS迁移代码后出现以下编译错误：

Error CS0103 The name 'UITextBorderStyle' does not exist in the current context EntryMAUIDemo (net7.0-ios) MauiProgram.cs 43 Active
Error CS0103 The name 'UIColor' does not exist in the current context EntryMAUIDemo (net7.0-ios) MauiProgram.cs 59 Active
Error CS1061 'MauiTextView' does not contain a definition for 'BorderStyle' and no accessible extension method 'BorderStyle' accepting a first argument of type 'MauiTextView' could be found (are you missing a using directive or an assembly reference?) EntryMAUIDemo (net7.0-ios) MauiProgram.cs 61 Active
Error CS0103 The name 'UITextBorderStyle' does not exist in the current context EntryMAUIDemo (net7.0-ios) MauiProgram.cs 61 Active

移除报错相关代码后运行，仍存在文本颜色问题：

• Entry文本颜色不显示，Entry占位符颜色异常
• Editor文本及占位符颜色均异常

截图说明 #

• 截图1：占位符显示正常
• 截图2：仅Editor文本颜色正常，Entry文本不可见

设备信息（Android问题复现设备） #

• 设备名称：OPPO A9 2020
• Android版本：11
• 型号：CPH1937

已将ModifyEntryandEditor()移至MauiProgram.cs，有更新后的示例项目可供复现。

内容的提问来源于stack exchange，提问作者Matthew Pans