MaterialApp home call build widget multi time. #23063
Description
i found the MaterialApp home widget call build multi time in multi case. i think it is issue.
case 1
the official example
import 'package:flutter/material.dart';
void main() {
runApp(MaterialApp(
title: 'Named Routes Demo',
// Start the app with the "/" named route. In our case, the app will start
// on the FirstScreen Widget
initialRoute: "/",
routes: {
"/": (context) => FirstScreen(),
// When we navigate to the "/second" route, build the SecondScreen Widget
'/second': (context) => SecondScreen(),
},
));
}
class FirstScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
print("first called");
return Scaffold(
appBar: AppBar(
title: Text('First Screen'),
),
body: Center(
child: RaisedButton(
child: Text('Launch screen'),
onPressed: () {
// Navigate to the second screen using a named route
Navigator.pushNamed(context, '/second');
},
),
),
);
}
}
class SecondScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
print("second called");
return Scaffold(
appBar: AppBar(
title: Text("Second Screen"),
),
body: Center(
child: RaisedButton(
onPressed: () {
// Navigate back to the first screen by popping the current route
// off the stack
Navigator.pop(context);
},
child: Text('Go back!'),
),
),
);
}
}the output log
Launching lib/main.dart on iPhone XS Max in debug mode...
Xcode build done. 4.4s
flutter: first called
flutter: first called
flutter: first called
it is ok when using home
void main() {
runApp(MaterialApp(
title: 'Named Routes Demo',
// Start the app with the "/" named route. In our case, the app will start
// on the FirstScreen Widget
home: FirstScreen(),
// initialRoute: "/",
routes: {
// "/": (context) => FirstScreen(),
// When we navigate to the "/second" route, build the SecondScreen Widget
'/second': (context) => SecondScreen(),
},
));
}Launching lib/main.dart on iPhone XS Max in debug mode...
Xcode build done. 4.2s
flutter: first called
case 2
when the home widget is stateful, it will call build every time when navigating to other router
import 'package:flutter/material.dart';
void main() {
runApp(MaterialApp(
title: 'Named Routes Demo',
// Start the app with the "/" named route. In our case, the app will start
// on the FirstScreen Widget
home: FirstScreen(),
// initialRoute: "/",
routes: {
// "/": (context) => FirstScreen(),
// When we navigate to the "/second" route, build the SecondScreen Widget
'/second': (context) => SecondScreen(),
},
));
}
class FirstScreen extends StatefulWidget {
@override
State<FirstScreen> createState() {
return FirstScreenState();
}
}
class FirstScreenState extends State<FirstScreen> {
@override
Widget build(BuildContext context) {
print("first called");
return Scaffold(
appBar: AppBar(
title: Text('First Screen'),
),
body: Center(
child: RaisedButton(
child: Text('Launch screen'),
onPressed: () {
// Navigate to the second screen using a named route
Navigator.pushNamed(context, '/second');
},
),
),
);
}
}
class SecondScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
print("second called");
return Scaffold(
appBar: AppBar(
title: Text("Second Screen"),
),
body: Center(
child: RaisedButton(
onPressed: () {
// Navigate back to the first screen by popping the current route
// off the stack
Navigator.pop(context);
},
child: Text('Go back!'),
),
),
);
}
}the output
Launching lib/main.dart on iPhone XS Max in debug mode...
Xcode build done. 4.3s
flutter: first called
flutter: second called
flutter: first called
if using routes
void main() {
runApp(MaterialApp(
title: 'Named Routes Demo',
// Start the app with the "/" named route. In our case, the app will start
// on the FirstScreen Widget
// home: FirstScreen(),
initialRoute: "/",
routes: {
"/": (context) => FirstScreen(),
// When we navigate to the "/second" route, build the SecondScreen Widget
'/second': (context) => SecondScreen(),
},
));
}the output
Launching lib/main.dart on iPhone XS Max in debug mode...
Xcode build done. 4.1s
flutter: first called
flutter: first called
flutter: first called
flutter: second called
flutter: first called
flutter analyze
Analyzing test1...
No issues found! (ran in 0.8s)
flutter doctor -v
[✓] Flutter (Channel beta, v0.9.4, on Mac OS X 10.13.6 17G65, locale en-CN)
• Flutter version 0.9.4 at /Users/vty/Pkg/flutter
• Framework revision f37c235c32 (3 weeks ago), 2018-09-25 17:45:40 -0400
• Engine revision 74625aed32
• Dart version 2.1.0-dev.5.0.flutter-a2eb050044
[✓] Android toolchain - develop for Android devices (Android SDK 27.0.3)
• Android SDK at /Users/vty/Library/Android/sdk
• Android NDK at /Users/vty/Library/Android/sdk/ndk-bundle
• Platform android-27, build-tools 27.0.3
• ANDROID_HOME = /Users/vty/Library/Android/sdk
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b01)
• All Android licenses accepted.
[✓] iOS toolchain - develop for iOS devices (Xcode 10.0)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 10.0, Build version 10A255
• ios-deploy 2.0.0
• CocoaPods version 1.5.3
[✓] Android Studio (version 3.1)
• Android Studio at /Applications/Android Studio.app/Contents
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b01)
[!] IntelliJ IDEA Community Edition (version 2018.1.6)
• IntelliJ at /Applications/IntelliJ IDEA CE.app
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
• For information about installing plugins, see
https://flutter.io/intellij-setup/#installing-the-plugins
[✓] VS Code (version 1.28.1)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 2.19.0
[✓] Connected devices (1 available)
• iPhone XS Max • D8A03577-F9B0-4DB3-B41D-FBB90838D81F • ios • iOS 12.0 (simulator)
! Doctor found issues in 1 category.