当我尝试加载LessonPage时，我不断收到错误消息。发生的是，我有一个RootPage，它会检查用户是否已登录，如果他是RootPage，则会显示LessonPage，但如果不是，它将显示{ {1}}，当用户登录时，将调用到LoginScreen RootPage的回调函数，以便将页面切换到_onLoggedIn()。
更新：我发现加载应用程序时（也就是应用程序打开到LessonPage）时也记录了错误，但是我看到的是登录屏幕，而不是空白屏幕。我在下面附加了LoginScreen代码以供参考
根页：
LoginScreen课程页面：
class RootPage extends StatefulWidget {
RootPage({this.auth});
final BaseAuth auth;
@override
State<StatefulWidget> createState() => new _RootPageState();
}
enum AuthStatus {
NOT_DETERMINED,
NOT_LOGGED_IN,
LOGGED_IN,
}
class _RootPageState extends State<RootPage> {
AuthStatus authStatus = AuthStatus.NOT_DETERMINED;
String _userId = "";
@override
void initState() {
super.initState();
widget.auth.getCurrentUser().then((user) {
setState(() {
if (user != null) {
_userId = user?.uid;
}
authStatus =
user?.uid == null ? AuthStatus.NOT_LOGGED_IN : AuthStatus.LOGGED_IN;
});
});
}
void _onLoggedIn() {
widget.auth.getCurrentUser().then((user){
setState(() {
_userId = user.uid.toString();
});
});
setState(() {
authStatus = AuthStatus.LOGGED_IN;
});
}
void _onSignedOut() {
setState(() {
authStatus = AuthStatus.NOT_LOGGED_IN;
_userId = "";
});
}
Widget _buildWaitingScreen() {
return Scaffold(
body: Container(
alignment: Alignment.center,
child:
ColorLoader5(
dotOneColor: Colors.blueGrey[600],
dotTwoColor: Colors.blueGrey[700],
dotThreeColor: Colors.blueGrey[800],
dotType: DotType.circle,
dotIcon: Icon(Icons.adjust),
duration: Duration(seconds: 1),
),
),
);
}
@override
Widget build(BuildContext context) {
switch (authStatus) {
case AuthStatus.NOT_DETERMINED:
return _buildWaitingScreen();
break;
case AuthStatus.NOT_LOGGED_IN:
return new LoginScreen(
auth: widget.auth,
onSignedIn: _onLoggedIn,
);
break;
case AuthStatus.LOGGED_IN:
if (_userId.length > 0 && _userId != null) {
return new Container(child: SingleChildScrollView(child: LessonPage(
title: LESSON_PAGE_TITLE,
userId: _userId,
auth: widget.auth,
onSignedOut: _onSignedOut,
)));
} else return _buildWaitingScreen();
break;
default:
return _buildWaitingScreen();
}
}
}
LoginScreen容器：
class LessonPage extends StatefulWidget {
LessonPage({Key key, this.auth, this.userId, this.onSignedOut, this.title}) : super(key: key);
final String title;
final BaseAuth auth;
final VoidCallback onSignedOut;
final String userId;
@override
_LessonPageState createState() => _LessonPageState();
}
class _LessonPageState extends State<LessonPage> {
List lessons;
@override
void initState() {
lessons = StaticMethods.getLessons();
super.initState();
}
@override
Widget build(BuildContext context) {
ListTile makeListTile(Lesson lesson) => ListTile(
contentPadding:
EdgeInsets.symmetric(horizontal: 20.0, vertical: 10.0),
leading: Container(
padding: EdgeInsets.only(right: 12.0),
decoration: new BoxDecoration(
border: new Border(
right: new BorderSide(width: 1.0, color: Colors.white24))),
child: IconButton(
icon: Icon(Icons.file_download, color: Colors.white),
onPressed: (){},
),
),
title: Text(
lesson.title,
style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
),
subtitle: Row(
children: <Widget>[
Expanded(
flex: 1,
child: Container(
child: LinearProgressIndicator(
backgroundColor: Color.fromRGBO(209, 224, 224, 0.2),
value: lesson.indicatorValue,
valueColor: AlwaysStoppedAnimation(Colors.green)),
)),
Expanded(
flex: 4,
child: Padding(
padding: EdgeInsets.only(left: 10.0),
child: Text(lesson.level,
style: TextStyle(color: Colors.white))),
)
],
),
trailing:
Icon(Icons.keyboard_arrow_right, color: Colors.white, size: 30.0),
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => DetailPage(lesson: lesson)));
},
);
Card makeCard(Lesson lesson) => Card(
elevation: 8.0,
margin: new EdgeInsets.symmetric(horizontal: 10.0, vertical: 6.0),
child: Container(
decoration: BoxDecoration(color: Color.fromRGBO(64, 75, 96, .9)),
child: makeListTile(lesson),
),
);
final makeBody = Container(
child: ListView.builder(
scrollDirection: Axis.vertical,
shrinkWrap: true,
itemCount: lessons.length,
itemBuilder: (BuildContext context, int index) {
return makeCard(lessons[index]);
},
),
);
final makeBottom = Container(
height: 55.0,
child: BottomAppBar(
color: Color.fromRGBO(58, 66, 86, 1.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
IconButton(
icon: Icon(Icons.school, color: Colors.white),
onPressed: () => StaticMethods.goToWidget(context, new LessonPage(title: LESSON_PAGE_TITLE)),
),
IconButton(
icon: Icon(Icons.flight_takeoff, color: Colors.white),
onPressed: () {},
),
IconButton(
icon: Icon(Icons.account_box, color: Colors.white),
onPressed: () {},
)
],
),
),
);
final topAppBar = AppBar(
elevation: 0.1,
backgroundColor: Color.fromRGBO(58, 66, 86, 1.0),
title: Text(widget.title),
automaticallyImplyLeading: false,
);
return Scaffold(
backgroundColor: Color.fromRGBO(58, 66, 86, 1.0),
appBar: topAppBar,
body: makeBody,
bottomNavigationBar: makeBottom,
);
}
}
错误：
Widget OptionPage() {
return new Container(
height: MediaQuery.of(context).size.height,
decoration: BoxDecoration(
color: Color.fromRGBO(58, 66, 86, 1.0),
image: DecorationImage(
colorFilter: new ColorFilter.mode(
Colors.black.withOpacity(0.1), BlendMode.dstATop),
image: AssetImage('assets/images/drones.jpg'),
fit: BoxFit.cover,
),
),
child: new Column(
children: <Widget>[
Container(
padding: EdgeInsets.only(top: 250.0),
child: Center(
child: Icon(
Icons.school,
color: Colors.white,
size: 40.0,
),
),
),
Container(
padding: EdgeInsets.only(top: 20.0),
child: new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
LOGIN_SCREEN_TITLE,
style: TextStyle(
color: Colors.white,
fontSize: 20.0,
),
),
],
),
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 30.0, right: 30.0, top: 150.0),
alignment: Alignment.center,
child: new Row(
children: <Widget>[
new Expanded(
child: new OutlineButton(
shape: new RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0)),
color: Color.fromRGBO(58, 66, 86, 1.0),
highlightedBorderColor: Colors.white,
onPressed: () => gotoSignup(),
child: new Container(
padding: const EdgeInsets.symmetric(
vertical: 20.0,
horizontal: 20.0,
),
child: new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Expanded(
child: Text(
LOGIN_SCREEN_SIGN_UP,
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontWeight: FontWeight.bold),
),
),
],
),
),
),
),
],
),
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 30.0, right: 30.0, top: 30.0),
alignment: Alignment.center,
child: new Row(
children: <Widget>[
new Expanded(
child: new FlatButton(
shape: new RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0)),
color: Colors.white,
onPressed: () => gotoLogin(),
child: new Container(
padding: const EdgeInsets.symmetric(
vertical: 20.0,
horizontal: 20.0,
),
child: new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Expanded(
child: Text(
LOGIN_SCREEN_LOGIN,
textAlign: TextAlign.center,
style: TextStyle(
color: Color.fromRGBO(58, 66, 86, 1.0),
fontWeight: FontWeight.bold),
),
),
],
),
),
),
),
],
),
),
],
),
);
}
Widget LoginPage() {
return new Container(
height: MediaQuery.of(context).size.height,
decoration: BoxDecoration(
color: Colors.white,
image: DecorationImage(
colorFilter: new ColorFilter.mode(
Colors.black.withOpacity(0.05), BlendMode.dstATop),
image: AssetImage('assets/images/drones.jpg'),
fit: BoxFit.cover,
),
),
child: new Column(
children: <Widget>[
Container(
padding: EdgeInsets.all(120.0),
child: Center(
child: Icon(
Icons.school,
color: Color.fromRGBO(58, 66, 86, 1.0),
size: 50.0,
),
),
),
new Row(
children: <Widget>[
new Expanded(
child: new Padding(
padding: const EdgeInsets.only(left: 40.0),
child: new Text(
LOGIN_SCREEN_EMAIL,
style: TextStyle(
fontWeight: FontWeight.bold,
color: Color.fromRGBO(58, 66, 86, 1.0),
fontSize: 15.0,
),
),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 40.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Expanded(
child: TextFormField( // LOGIN SCREEN EMAIL
maxLines: 1,
keyboardType: TextInputType.emailAddress,
autofocus: false,
textAlign: TextAlign.left,
decoration: InputDecoration(
icon: Icon(Icons.alternate_email),
hintText: LOGIN_SCREEN_EMAIL_HINT,
hintStyle: TextStyle(color: Colors.grey),
),
validator: (value) => value.isEmpty ? LOGIN_SCREEN_EMAIL_WARNING : null,
onSaved: (value) => _email = value,
),
),
],
),
),
Divider(
height: 24.0,
color: Color(0x00000000),
),
new Row(
children: <Widget>[
new Expanded(
child: new Padding(
padding: const EdgeInsets.only(left: 40.0),
child: new Text(
LOGIN_SCREEN_PASSWORD,
style: TextStyle(
fontWeight: FontWeight.bold,
color: Color.fromRGBO(58, 66, 86, 1.0),
fontSize: 15.0,
),
),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 40.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Expanded(
child: TextFormField( // LOGIN SCREEN PASSWORD
obscureText: true,
keyboardType: TextInputType.emailAddress,
maxLines: 1,
autofocus: false,
textAlign: TextAlign.left,
decoration: InputDecoration(
icon: Icon(Icons.lock_outline),
hintText: LOGIN_SCREEN_PASSWORD_HINT,
hintStyle: TextStyle(color: Colors.grey),
),
validator: (value) => value.isEmpty ? LOGIN_SCREEN_PASSWORD_WARNING : null,
onSaved: (value) => _password = value,
),
),
],
),
),
Divider(
height: 24.0,
color: Color(0x00000000),
),
new Row(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(right: 20.0),
child: new FlatButton(
child: new Text(
LOGIN_SCREEN_FORGOT_PASSWORD,
style: TextStyle(
fontWeight: FontWeight.bold,
color: Color.fromRGBO(58, 66, 86, 1.0),
fontSize: 15.0,
),
textAlign: TextAlign.end,
),
onPressed: () => StaticMethods.locked(context),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 30.0, right: 30.0, top: 20.0),
alignment: Alignment.center,
child: new Row(
children: <Widget>[
new Expanded(
child: new FlatButton( // LOGIN SCREEN LOGIN BUTTON
shape: new RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0),
),
color: Color.fromRGBO(58, 66, 86, 1.0),
onPressed: () => _validateAndSubmit(),
child: new Container(
padding: const EdgeInsets.symmetric(
vertical: 20.0,
horizontal: 20.0,
),
child: new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Expanded(
child: Text(
LOGIN_SCREEN_LOGIN,
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontWeight: FontWeight.bold),
),
),
],
),
),
),
),
],
),
),
Divider(
height: 25.0,
color: Color(0x00000000),
),
_showErrorMessage(),
Divider(
height: 25.0,
color: Color(0x00000000),
),
_showLoading(),
],
),
);
}
Widget SignupPage() {
return new Container(
height: MediaQuery.of(context).size.height,
decoration: BoxDecoration(
color: Colors.white,
image: DecorationImage(
colorFilter: new ColorFilter.mode(
Colors.black.withOpacity(0.05), BlendMode.dstATop),
image: AssetImage('assets/images/drones.jpg'),
fit: BoxFit.cover,
),
),
child: new Column(
children: <Widget>[
Container(
padding: EdgeInsets.all(100.0),
child: Center(
child: Icon(
Icons.school,
color: Color.fromRGBO(58, 66, 86, 1.0),
size: 50.0,
),
),
),
new Row(
children: <Widget>[
new Expanded(
child: new Padding(
padding: const EdgeInsets.only(left: 40.0),
child: new Text(
LOGIN_SCREEN_EMAIL,
style: TextStyle(
fontWeight: FontWeight.bold,
color: Color.fromRGBO(58, 66, 86, 1.0),
fontSize: 15.0,
),
),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 40.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Expanded(
child: TextField( //SIGNUP SCREEN EMAIL
obscureText: true,
textAlign: TextAlign.left,
decoration: InputDecoration(
hintText: LOGIN_SCREEN_EMAIL_HINT,
hintStyle: TextStyle(color: Colors.grey),
),
),
),
],
),
),
Divider(
height: 24.0,
color: Color(0x00000000),
),
new Row(
children: <Widget>[
new Expanded(
child: new Padding(
padding: const EdgeInsets.only(left: 40.0),
child: new Text(
LOGIN_SCREEN_PASSWORD,
style: TextStyle(
fontWeight: FontWeight.bold,
color: Color.fromRGBO(58, 66, 86, 1.0),
fontSize: 15.0,
),
),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 40.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Expanded(
child: TextField( // SIGNUP SCREEN PASSWORD
obscureText: true,
textAlign: TextAlign.left,
decoration: InputDecoration(
hintText: LOGIN_SCREEN_PASSWORD_HINT,
hintStyle: TextStyle(color: Colors.grey),
),
),
),
],
),
),
Divider(
height: 24.0,
color: Color(0x00000000),
),
new Row(
children: <Widget>[
new Expanded(
child: new Padding(
padding: const EdgeInsets.only(left: 40.0),
child: new Text( // SIGNUP SCREEN CONFIRM PASSWORD
LOGIN_SCREEN_CONFIRM_PASSWORD,
style: TextStyle(
fontWeight: FontWeight.bold,
color: Color.fromRGBO(58, 66, 86, 1.0),
fontSize: 15.0,
),
),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 40.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Expanded(
child: TextField(
obscureText: true,
textAlign: TextAlign.left,
decoration: InputDecoration(
hintText: LOGIN_SCREEN_PASSWORD_HINT,
hintStyle: TextStyle(color: Colors.grey),
),
),
),
],
),
),
Divider(
height: 24.0,
color: Color(0x00000000),
),
new Row(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(right: 20.0),
child: new FlatButton(
child: new Text(
LOGIN_SCREEN_HAVE_ACCOUNT,
style: TextStyle(
fontWeight: FontWeight.bold,
color: Color.fromRGBO(58, 66, 86, 1.0),
fontSize: 15.0,
),
textAlign: TextAlign.end,
),
onPressed: () => StaticMethods.locked(context),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 30.0, right: 30.0, top: 50.0),
alignment: Alignment.center,
child: new Row(
children: <Widget>[
new Expanded(
child: new FlatButton( // SIGNUP SCREEN SIGN UP BUTTON
shape: new RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0),
),
color: Color.fromRGBO(58, 66, 86, 1.0),
onPressed: () => StaticMethods.locked(context),
child: new Container(
padding: const EdgeInsets.symmetric(
vertical: 20.0,
horizontal: 20.0,
),
child: new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Expanded(
child: Text(
LOGIN_SCREEN_SIGN_UP,
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontWeight: FontWeight.bold),
),
),
],
),
),
),
),
],
),
),
],
),
);
}
PageController _controller = new PageController(initialPage: 1, viewportFraction: 1.0);
@override
Widget build(BuildContext context) {
_isIos = Theme.of(context).platform == TargetPlatform.iOS;
return Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
child: new Form (
key: _formKey,
child: PageView(
controller: _controller,
physics: new AlwaysScrollableScrollPhysics(),
children: <Widget>[LoginPage(), OptionPage(), SignupPage()],
scrollDirection: Axis.horizontal,
onPageChanged: (num){
switch (num) {
case 0:
setState(() {
_formKey.currentState.reset();
_errorMessage = "";
_formMode = FormMode.LOGIN;
});
break;
case 1:
setState(() {
_formKey.currentState.reset();
_errorMessage = "";
_formMode = FormMode.OPTIONS;
});
break;
case 2:
setState(() {
_formKey.currentState.reset();
_errorMessage = "";
_formMode = FormMode.SIGNUP;
});
break;
}
},
),
),
);
}
在错误中，它仅显示空白页面而不是课程页面，并且检查firebase可以看到用户登录，因此我认为这是一些布局问题。
我尝试过的事情：
RootPage（我仍然看到一个空白屏幕）：
I/flutter (18510): The following assertion was thrown during performLayout():
I/flutter (18510): RenderCustomMultiChildLayoutBox object was given an infinite size during layout.
.....
我试图返回一个普通页面，而不是课程页面，该页面仅显示了一个已经过测试并且可以正常工作的加载动画，但是我仍然看到一个空白页面：
return new LessonPage(
title: LESSON_PAGE_TITLE,
userId: _userId,
auth: widget.auth,
onSignedOut: _onSignedOut,
);
LessonPage（仍然看到空白页）：
return _buildWaitingScreen();
答案 0 :(得分：1)
下面的代码段中不需要def options(self, *args):
...
和Container：
SingleChildScrollView如果仍然无法解决，
return LessonPage(
title: LESSON_PAGE_TITLE,
userId: _userId,
auth: widget.auth,
onSignedOut: _onSignedOut,
);
意味着您使用了RenderCustomMultiChildLayoutBox object was given an infinite size during layout.或ListView或任何其他具有无限大小的小部件。为了防止出现此问题，请用固定大小包装ScrollView列表视图。如果工作正常，则可以使用makeBody（赋予设备屏幕宽度）并调整您想要的尺寸。
例如：
MediaQuery.of(context).size.height并调用方法：Widget makeBody(BuildContext context) => Container(
height: MediaQuery.of(context).size.height / 1.5,
child: ListView.builder(
scrollDirection: Axis.vertical,
shrinkWrap: true,
itemCount: lessons.length,
itemBuilder: (BuildContext context, int index) {
return makeCard(lessons[index]);
},
),
);
修正body: makeBody(context),：
RootPage