Flutter：问题收录

本文主要是介绍Flutter：问题收录，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

文章目录

Missing Xcode dependency: Python module "six"
- 参考
Navigator operation requested with a context that does not include a Navigator
- 原因
Scaffold.of() called with a context that does not contain a Scaffold.
- 原因
Waiting for another flutter command to release the startup lock
TextField 的 HintText不垂直居中
flutter doctor --android-licenses
Cannot find declaration to go to

Missing Xcode dependency: Python module “six”

按照建议使用pip install six和 sudo easy_install six没用，使用python2.x -m pip install six或者 brew reinstall python@2和
pip install six解决。

参考

Missing xcode dependency: Python module “six”

Navigator operation requested with a context that does not include a Navigator

在写页面跳转的时候报出了该错误：

void main() => runApp(new MyApp());class MyApp extends StatelessWidget {// This widget is the root of your application.@overrideWidget build(BuildContext context) {return new MaterialApp(title: 'Flutter Test',home: new Scaffold(appBar: new AppBar(title: new Text("Flutter Test"),),body: new Column(children: <Widget>[new RaisedButton(onPressed: () {Navigator.push(context,new MaterialPageRoute(builder: (context) => new BasicWidget()));},child: new Text('基本组件'),)],),),);}
}

修改为以下即可，把Scafford独立出widget出来。

void main() => runApp(new MyApp());class MyApp extends StatelessWidget {// This widget is the root of your application.@overrideWidget build(BuildContext context) {return new MaterialApp(title: 'Flutter Test',home: new HomeWidget(),);}
}class HomeWidget extends StatelessWidget{@overrideWidget build(BuildContext context) {return new Scaffold(appBar: new AppBar(title: new Text("Flutter Text"),),body: new Column(children: <Widget>[new RaisedButton(onPressed: () {Navigator.push(context,new MaterialPageRoute(builder: (context) => new BasicWidget()),);},child: new Text('基本组件'),)],),);}
}

原因

BuildContext-class
Flutter by Example BuildContext Class
What does BuildContext do in Flutter?

Scaffold.of() called with a context that does not contain a Scaffold.

调用Scaffold.of(context).showSnackBar(snackBar);的时候报错：

I/flutter (24518): The following assertion was thrown while handling a gesture:
I/flutter (24518): Scaffold.of() called with a context that does not contain a Scaffold.
I/flutter (24518): No Scaffold ancestor could be found starting from the context that was passed to Scaffold.of(). This
I/flutter (24518): usually happens when the context provided is from the same StatefulWidget as that whose build
I/flutter (24518): function actually creates the Scaffold widget being sought.
I/flutter (24518): There are several ways to avoid this problem. The simplest is to use a Builder to get a context that
I/flutter (24518): is “under” the Scaffold. For an example of this, please see the documentation for Scaffold.of():
I/flutter (24518): https://docs.flutter.io/flutter/material/Scaffold/of.html
I/flutter (24518): A more efficient solution is to split your build function into several widgets. This introduces a
I/flutter (24518): new context from which you can obtain the Scaffold. In this solution, you would have an outer widget
I/flutter (24518): that creates the Scaffold populated by instances of your new inner widgets, and then in these inner
I/flutter (24518): widgets you would use Scaffold.of().
I/flutter (24518): A less elegant but more expedient solution is assign a GlobalKey to the Scaffold, then use the
I/flutter (24518): key.currentState property to obtain the ScaffoldState rather than using the Scaffold.of() function.
I/flutter (24518): The context used was:
I/flutter (24518): BasicWidget

class BasicWidget extends StatelessWidget {@overrideWidget build(BuildContext context) {return new Scaffold(appBar: new AppBar(title: new Text("Basic Widget"),),body: new Column(children: <Widget>[new RaisedButton(onPressed: () {final snackBar = new SnackBar(content: new Text("这是一个Snackbar"),action: new SnackBarAction(label: "Undo",onPressed: (){}),);Scaffold.of(context).showSnackBar(snackBar);},child: new Text("显示Snackbar"),)],));}
}

改成：

class BasicWidget extends StatelessWidget {@overrideWidget build(BuildContext context) {return new Scaffold(appBar: new AppBar(title: new Text("Basic Widget"),),body: new Builder(builder: (BuildContext context){return new Column(children: <Widget>[new RaisedButton(onPressed: () {final snackBar = new SnackBar(content: new Text("这是一个Snackbar"),action: new SnackBarAction(label: "Undo",onPressed: (){}),);Scaffold.of(context).showSnackBar(snackBar);},child: new Text("显示Snackbar"),)],);}),);}
}

或者我们也可以把Column抽出来：

class BasicWidget extends StatelessWidget {@overrideWidget build(BuildContext context) {return new Scaffold(appBar: new AppBar(title: new Text("Basic Widget"),),body: new BasicColumnWidget());}
}class BasicColumnWidget extends StatelessWidget {@overrideWidget build(BuildContext context) {// TODO: implement buildreturn new Column(children: <Widget>[new RaisedButton(onPressed: () {final snackBar = new SnackBar(content: new Text("这是一个Snackbar"),action: new SnackBarAction(label: "Undo", onPressed: () {}),);Scaffold.of(context).showSnackBar(snackBar);},child: new Text("显示Snackbar"),)],);}
}

原因

of method

Waiting for another flutter command to release the startup lock

终端使用命令flutter packages pub build_runner watch

TextField 的 HintText不垂直居中

textStyle里使用textStyle : TextStyle(textBaseline: TextBaseline.alphabetic)

flutter doctor --android-licenses

使用flutter doctor --android-licenses命令的时候报以下错误：

Exception in thread “main” java.lang.NoClassDefFoundError: javax/xml/bind/annotation/XmlSchema
at com.android.repository.api.SchemaModule $S c h e m a M o d u l e V e r s i o n . < i n i t > (S c h e m a M o d u l e . j a v a : 156) a t c o m . a n d r o i d . r e p o s i t o r y . a p i . S c h e m a M o d u l e . < i n i t > (S c h e m a M o d u l e . j a v a : 75) a t c o m . a n d r o i d . s d k l i b . r e p o s i t o r y . A n d r o i d S d k H a n d l e r . < c l i n i t > (A n d r o i d S d k H a n d l e r . j a v a : 81) a t c o m . a n d r o i d . s d k l i b . t o o l . s d k m a n a g e r . S d k M a n a g e r C l i . m a i n (S d k M a n a g e r C l i . j a v a : 73) a t c o m . a n d r o i d . s d k l i b . t o o l . s d k m a n a g e r . S d k M a n a g e r C l i . m a i n (S d k M a n a g e r C l i . j a v a : 48) C a u s e d b y : j a v a . l a n g . C l a s s N o t F o u n d E x c e p t i o n : j a v a x . x m l . b i n d . a n n o t a t i o n . X m l S c h e m a a t j a v a . b a s e / j d k . i n t e r n a l . l o a d e r . B u i l t i n C l a s s L o a d e r . l o a d C l a s s (B u i l t i n C l a s s L o a d e r . j a v a : 581) a t j a v a . b a s e / j d k . i n t e r n a l . l o a d e r . C l a s s L o a d e r s$ AppClassLoader.loadClass(ClassLoaders.java:178)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
… 5 more