dart - 如何将 CupertinoApp 包装在 Localizations 小部件中，以便我可以在其中使用 Material 小部件？

Question

我正在使用 CupertinoApp 小部件来包装我的应用程序，同时尝试在其中使用 Material TextFormField 小部件。

例如，当我触发文本选择模式(双击文本字段)时，出现以下错误(因为它试图打开一个需要 Material 本地化的叠加小部件):

错误信息

未找到 MaterialLocalizations。OverlayEntry 小部件需要由 Localizations 小部件祖先提供的 MaterialLocalizations。

本地化用于生成 Material 库使用的许多不同消息、标签和缩写。

要引入 MaterialLocalizations，请在您的应用程序的根部使用 MaterialApp 以:自动包含它们，或添加带有 MaterialLocalizations 委托(delegate)的 Localization 小部件。

---

问题是我不能使用 MaterialApp，因为我需要使用 Cupertino 风格的导航(CupertinoTabBar/CupertinoTabView 中的嵌套导航器)，所以我需要使用 Localization 小部件方法。

但是下面的代码并没有解决问题:

void main() {
  runApp(
    Localizations(
      child: CupertinoApp(
        debugShowCheckedModeBanner: false,
        home: App(), // <-- Main Screen, a Cupertino Tab Scaffold with 3 CupertinoTabViews
      ),
      locale: Locale('en', 'US'),
      delegates: <LocalizationsDelegate>[

        // I assumed these were sufficient, but the runtime exception still persist.
        DefaultMaterialLocalizations.delegate,
        DefaultCupertinoLocalizations.delegate,
        DefaultWidgetsLocalizations.delegate,
      ],
    ),
  );
}

那么我的问题是，执行此操作的正确方法是什么，是否不能在 CupertinoApp 中使用 Material 小部件？

I/flutter ( 7631): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 7631): The following assertion was thrown building
I/flutter ( 7631): _OverlayEntry-[LabeledGlobalKey<_OverlayEntryState>#1e5c6](dirty, dependencies:
I/flutter ( 7631): [_LocalizationsScope-[GlobalKey#d1cfa]], state: _OverlayEntryState#ba2a3):
I/flutter ( 7631): No MaterialLocalizations found.
I/flutter ( 7631): _OverlayEntry widgets require MaterialLocalizations to be provided by a Localizations widget
I/flutter ( 7631): ancestor.
I/flutter ( 7631): Localizations are used to generate many different messages, labels,and abbreviations which are used
I/flutter ( 7631): by the material library. 
I/flutter ( 7631): To introduce a MaterialLocalizations, either use a  MaterialApp at the root of your application to
I/flutter ( 7631): include them automatically, or add a Localization widget with a MaterialLocalizations delegate.
I/flutter ( 7631): The specific widget that could not find a MaterialLocalizations ancestor was:
I/flutter ( 7631):   _OverlayEntry-[LabeledGlobalKey<_OverlayEntryState>#1e5c6]
I/flutter ( 7631): The ancestors of this widget were:
I/flutter ( 7631):   Stack(alignment: AlignmentDirectional.topStart, fit: expand, overflow: clip)
I/flutter ( 7631):   _Theatre
I/flutter ( 7631):   Overlay-[LabeledGlobalKey<OverlayState>#362c7]
I/flutter ( 7631):   _FocusScopeMarker
I/flutter ( 7631):   Semantics(container: false, properties: SemanticsProperties, label: null, value: null, hint: null,
I/flutter ( 7631):   hintOverrides: null)
I/flutter ( 7631):   FocusScope
I/flutter ( 7631):   AbsorbPointer(absorbing: false)
I/flutter ( 7631):   Listener(listeners: [down, up, cancel], behavior: deferToChild)
I/flutter ( 7631):   Navigator-[GlobalObjectKey<NavigatorState> _WidgetsAppState#2397a]
I/flutter ( 7631):   DefaultTextStyle(inherit: false, color: Color(0xff000000), family: .SF Pro Text, size: 17.0,
I/flutter ( 7631):   letterSpacing: -0.4, decoration: TextDecoration.none, softWrap: wrapping at box width, overflow:
I/flutter ( 7631):   clip)
I/flutter ( 7631):   Title(color: Color(0xff007aff))
I/flutter ( 7631):   Directionality(textDirection: ltr)
I/flutter ( 7631):   _LocalizationsScope-[GlobalKey#d1cfa]
I/flutter ( 7631):   Semantics(container: false, properties: SemanticsProperties, label: null, value: null, hint: null,
I/flutter ( 7631):   textDirection: ltr, hintOverrides: null)
I/flutter ( 7631):   Localizations(locale: en_US, delegates: [DefaultCupertinoLocalizations.delegate(en_US),
I/flutter ( 7631):   DefaultWidgetsLocalizations.delegate(en_US)])
I/flutter ( 7631):   MediaQuery(MediaQueryData(size: Size(411.4, 683.4), devicePixelRatio: 2.6, textScaleFactor: 1.0,
I/flutter ( 7631):   platformBrightness: Brightness.light, padding: EdgeInsets(0.0, 24.0, 0.0, 0.0), viewInsets:
I/flutter ( 7631):   EdgeInsets.zero, alwaysUse24HourFormat: false, accessibleNavigation: falsedisableAnimations:
I/flutter ( 7631):   falseinvertColors: falseboldText: false))
I/flutter ( 7631):   WidgetsApp-[GlobalObjectKey _CupertinoAppState#5df27]
I/flutter ( 7631):   IconTheme(IconThemeData#33904(color: Color(0xff007aff)))
I/flutter ( 7631):   _InheritedCupertinoTheme
I/flutter ( 7631):   CupertinoTheme
I/flutter ( 7631):   ScrollConfiguration(behavior: _AlwaysCupertinoScrollBehavior)
I/flutter ( 7631):   CupertinoApp
I/flutter ( 7631):   Directionality(textDirection: ltr)
I/flutter ( 7631):   _LocalizationsScope-[GlobalKey#dfb7d]
I/flutter ( 7631):   Semantics(container: false, properties: SemanticsProperties, label: null, value: null, hint: null,
I/flutter ( 7631):   textDirection: ltr, hintOverrides: null)
I/flutter ( 7631):   Localizations(locale: en_US, delegates: [DefaultMaterialLocalizations.delegate(en_US),
I/flutter ( 7631):   DefaultCupertinoLocalizations.delegate(en_US), DefaultWidgetsLocalizations.delegate(en_US)])
I/flutter ( 7631):   _InheritedModel<AppModel>
I/flutter ( 7631):   AnimatedBuilder(animation: Instance of 'AppModel')
I/flutter ( 7631):   ScopedModel<AppModel>
I/flutter ( 7631):   [root]
I/flutter ( 7631): 
I/flutter ( 7631): When the exception was thrown, this was the stack:
I/flutter ( 7631): #0      debugCheckHasMaterialLocalizations.<anonymous closure> (package:flutter/src/material/debug.dart:124:7)
I/flutter ( 7631): #1      debugCheckHasMaterialLocalizations (package:flutter/src/material/debug.dart:127:4)
I/flutter ( 7631): #2      _MaterialTextSelectionControls.buildToolbar (package:flutter/src/material/text_selection.dart:135:12)
// ....

Answer 1

您不应将 CupertinoApp 包装到 Localization 中。

CupertinoApp 包括插入它自己的 Localization 小部件，因此无论您在 CupertinoApp 上面添加什么，都会被覆盖。

相反，将您的委托(delegate)直接传递给 CupertinoApp 的 localizationsDelegates:

CupertinoApp(
  localizationsDelegates: [
    DefaultMaterialLocalizations.delegate,
    DefaultCupertinoLocalizations.delegate,
    DefaultWidgetsLocalizations.delegate,
  ],
),