Dart 在颤振图标中，按钮在appBar中单击，但出现错误

我一直试图触发一个对话框时，图标按钮是点击在appBar，但错误来了

这个错误是持久性的

我认为showDialog（）中传递的上下文有一些问题，我不确定 进口“包装：颤振/材料.省道”； 进口“包装：Flatter_colorpicker/Flatter_colorpicker.dart”

void main() => runApp(new MyApp());

class MyApp extends StatefulWidget {
## Heading ##
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return _MyPortfolioState();
  }
}

class _MyPortfolioState extends State<MyApp> {
  MaterialColor primaryColor = Colors.blue;
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        title: 'Portfolio',
        theme: new ThemeData(
          primarySwatch: primaryColor,
        ),
        home: Scaffold(
            appBar: AppBar(
                title: Text("Dhruv Agarwal"),
                textTheme: TextTheme(
                    display2: TextStyle(color: Color.fromARGB(1, 0, 0, 0))),
                actions: <Widget>[
              new IconButton(
                icon: Icon(Icons.format_color_text),
                tooltip: 'Change Color',
                onPressed: () {
                  Color pickerColor = primaryColor;
                  changeColor(Color color) {
                    setState(() => primaryColor = color);
                  }
                  showDialog (
                      context: context,
                      builder: (BuildContext context) {
                        return AlertDialog(
                          title: const Text('Pick a color!'),
                          content: SingleChildScrollView(
                            child: ColorPicker(
                              pickerColor: pickerColor,
                              onColorChanged: changeColor,
                              pickerAreaHeightPercent: 0.8,
                            ),
                          ),
                          actions: <Widget>[
                            FlatButton(
                              child: Text('Got it'),
                              onPressed: () {
                                setState(() => primaryColor = pickerColor);
                                Navigator.of(context).pop();
                              },
                            ),
                          ],
                        );
                      });
                },
              ),
            ])));
  }
}

//
//

void main（）=>runApp（新的MyApp（））；
类MyApp扩展了StatefulWidget{
##标题##
@凌驾
状态createState（）{
//TODO:实现createState
返回_MyPortfolioState（）；
}
}
类_MyPortfolioState扩展状态{
MaterialColor primaryColor=Colors.blue；
//此小部件是应用程序的根。
@凌驾
小部件构建（构建上下文）{
返回材料PP(
标题：“投资组合”，
主题：新主题数据(
primarySwatch:primaryColor，
),
家：脚手架(
appBar:appBar(
标题：文本（“Dhruv Agarwal”），
textTheme:textTheme(
display2:TextStyle（颜色：color.fromARGB（1,0,0）），
行动：[
新图标按钮(
图标：图标（图标。格式\颜色\文本），
工具提示：“更改颜色”，
已按下：（）{
颜色选择器颜色=原色；
更改颜色（颜色）{
设置状态（（）=>primaryColor=color）；
}
显示对话框(
上下文：上下文，
生成器：（BuildContext上下文）{
返回警报对话框(
标题：常量文本（'选择颜色！'），
内容：SingleChildScrollView(
孩子：色彩采集器(
pickerColor:pickerColor，
变色，
选择器高度百分比：0.8，
),
),
行动：[
扁平按钮(
child:Text（'Got it'），
已按下：（）{
设置状态（（）=>primaryColor=pickerColor）；
Navigator.of（context.pop（）；
},
),
],
);
});
},
),
])));
}
}
//
//

重新加载时引发异常，未找到MaterialLocalization

Launching lib/main.dart on Redmi Note 5 Pro in debug mode...
Initializing gradle...
Resolving dependencies...
Gradle task 'assembleDebug'...
Built build/app/outputs/apk/debug/app-debug.apk.
Installing build/app/outputs/apk/app.apk...
I/zygote64(16669): Do partial code cache collection, code=28KB, data=20KB
I/zygote64(16669): After code cache collection, code=28KB, data=20KB
I/zygote64(16669): Increasing code cache capacity to 128KB
Syncing files to device Redmi Note 5 Pro...
I/flutter (16669): ══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════
I/flutter (16669): The following assertion was thrown while handling a gesture:
I/flutter (16669): No MaterialLocalizations found.
I/flutter (16669): MyApp widgets require MaterialLocalizations to be provided by a Localizations widget ancestor.
I/flutter (16669): Localizations are used to generate many different messages, labels,and abbreviations which are used
I/flutter (16669): by the material library. 
I/flutter (16669): To introduce a MaterialLocalizations, either use a  MaterialApp at the root of your application to
I/flutter (16669): include them automatically, or add a Localization widget with a MaterialLocalizations delegate.
I/flutter (16669): The specific widget that could not find a MaterialLocalizations ancestor was:
I/flutter (16669):   MyApp
I/flutter (16669): The ancestors of this widget were:
I/flutter (16669):   [root]
I/flutter (16669): 
I/flutter (16669): When the exception was thrown, this was the stack:
I/flutter (16669): #0      debugCheckHasMaterialLocalizations.<anonymous closure> (package:flutter/src/material/debug.dart:124:7)
I/flutter (16669): #1      debugCheckHasMaterialLocalizations (package:flutter/src/material/debug.dart:127:4)
I/flutter (16669): #2      showDialog (package:flutter/src/material/dialog.dart:606:10)
I/flutter (16669): #3      MyApp.build.<anonymous closure> (file:///home/punisher/AndroidStudioProjects/first_app/portfolio/lib/main.dart:32:19)
I/flutter (16669): #4      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:507:14)
I/flutter (16669): #5      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:562:30)
I/flutter (16669): #6      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:102:24)
I/flutter (16669): #7      TapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:242:9)
I/flutter (16669): #8      TapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:204:7)
I/flutter (16669): #9      GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:156:27)
I/flutter (16669): #10     _WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:147:20)
I/flutter (16669): #11     _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:121:22)
I/flutter (16669): #12     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:101:7)
I/flutter (16669): #13     _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:64:7)
I/flutter (16669): #14     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:48:7)
I/flutter (16669): #15     _invoke1 (dart:ui/hooks.dart:153:13)
I/flutter (16669): #16     _dispatchPointerDataPacket (dart:ui/hooks.dart:107:5)
I/flutter (16669): 
I/flutter (16669): Handler: onTap
I/flutter (16669): Recognizer:
I/flutter (16669):   TapGestureRecognizer#5070d(debugOwner: GestureDetector, state: ready, won arena, finalPosition:
I/flutter (16669):   Offset(354.2, 64.0), sent tap down)
I/flutter (16669): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter (16669): Another exception was thrown: No MaterialLocalizations found.

在调试模式下在Redmi Note 5 Pro上启动lib/main.dart。。。
正在初始化gradle。。。
正在解析依赖项。。。
Gradle任务“assembleDebug”。。。
构建build/app/outputs/apk/debug/app-debug.apk。
正在安装build/app/outputs/apk/app.apk。。。
I/zygote64（16669）：执行部分代码缓存收集，代码=28KB，数据=20KB
I/zygote64（16669）：在代码缓存收集之后，代码=28KB，数据=20KB
I/zygote64（16669）：将代码缓存容量增加到128KB
正在将文件同步到设备Redmi Note 5 Pro。。。
I/颤振（16669）：══╡ 用手势捕捉异常╞═══════════════════════════════════════════════════════════════════
I/flatter（16669）：在处理手势时抛出以下断言：
I/颤振（16669）：未发现材料定位。
I/flatter（16669）：MyApp小部件要求本地化小部件祖先提供MaterialLocalization。
I/颤振（16669）：本地化用于生成许多不同的消息、标签和缩写
I/颤振（16669）：由材料库提供。
I/flatter（16669）：要引入MaterialLocalization，可以在应用程序的根目录下使用MaterialApp
I/flatter（16669）：自动包含它们，或者添加带有MaterialLocalizations委托的本地化小部件。
I/flatter（16669）：找不到MaterialLocalizations祖先的特定小部件是：
I/颤振（16669）：MyApp
I/flatter（16669）：这个小部件的祖先是：
I/颤振（16669）：[根]
I/颤振（16669）：
I/flatter（16669）：当抛出异常时，这是堆栈：
I/颤振（16669）：#0调试检查HasMaterialLocalization。（包：颤振/src/material/debug.dart:124:7）
I/flatter（16669）：#1调试检查hasMaterialLocalization（包：flatter/src/material/debug.dart:127:4）
I/flatter（16669）：#2 showDialog（包：flatter/src/material/dialog.dart:606:10）
I/颤振（16669）：#3 MyApp.build。(file:///home/punisher/AndroidStudioProjects/first_app/portfolio/lib/main.dart:32:19)
I/颤振（16669）：#4(InkResponseEstate.)(handleTap)(包装：颤振/src/材料/墨水)井。省道：507:14）
I/flatter（16669）：#5#InkResponseState.build。（包装：颤振/src/材料/墨水井。省道：562:30）
I/flatter（16669）：#6 GestureRecognizer.invokeCallback（包：flatter/src/signatures/recognizer.dart:102:24）
I/flatter（16669）：#7 TapGestureRecognitor.#检查（包：flatter/src/signatures/tap.dart:242:9）
I/flatter（16669）：#8 TapGestureRecognitor.Accept手势（包：flatter/src/signatures/tap.dart:204:7）
I/flatter（16669）：#9 GestureArenaManager.sweep（包：flatter/src/signatures/arena.dart:156:27）
I/flatter（16669）：#10#WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent（包：flatter/src/signatures/binding.dart:147:20）
I/flatter（16669）：11_WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent（包：flatter/src/signatures/binding.dart:121:22）
I/flatter（16669）：#12#WidgetsFlutterBinding&BindingBase&GestureBinding.#handlePointerEvent（包：flatter/src/signatures/binding.dart:101:7）
I/Flatter（16669）：#13#WidgetsFlutterBinding&BindingBase&GestureBinding.#flushPointerEventQueue（包装：Flatter/src/gest
main() => runApp(
      MaterialApp(
        title: 'ColorPicker test',
        home: MyApp(),
      ),
    );