Menu
I have this very basic test app:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
print("ROOT WIDGET ");
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Container(decoration: BoxDecoration(color: Colors.blue),),
);
}
}
Log output debug:
Launching lib/main.dart on iPhone X in debug mode...
Found saved certificate choice "XXX". To clear, use "flutter config". Signing iOS app for device deployment using developer identity: "XXX"
Running Xcode build...
Xcode build done. 39,4s
Installing and launching...
flutter: ROOT WIDGET
Syncing files to device iPhone X...
flutter: ROOT WIDGET
Log output with flutter run --release
Launching lib/main.dart on iPhone X in release mode...
Found saved certificate choice "XXX". To clear, use "flutter config".
Signing iOS app for device deployment using developer identity: "XXX"
Running pod install...
1,2sRunning Xcode build...
├─Building Dart code... 15,8s├─Generating dSYM file... 0,1s
├─Stripping debug symbols... 0,0s
├─Assembling Flutter resources... 0,7s
└─Compiling, linking and signing... 48,3s
Xcode build done. 67,4s
Installing and launching...
6,8sTo quit, press "q".
flutter: ROOT WIDGET
As you can see it only happens in debug mode.
The reason why I ask is, in my real app, I use a WebView. The function onWebViewCreated(WebViewController controller) of the WebView is only called the first time, so that the WebViewController is always null in debug mode.
538
One of the easiest ways to avoid unwanted reBuilds that are caused usually by calling setState() in order to update only a specific Widget and not refreshing the whole page, is to cut that part of your code and wrap it as an independent Widget in another Stateful class.
The MyApp is the root widget, and it is the parent of all the widgets in the tree. The MyApp widget renders the Container widget, and the Container widget renders the Row widget. The Row widget renders both Text and FlatButton widgets.
Flutter uses composition in building widgets, i.e., widgets are composed of other widgets. These widgets make the app UI. The following is an example using composition to compose BusinessCardWidget widget. BusinessCardWidget is composed of CircleAvatar , Column , Row , and Text widgets.
How build () method works how it rebuild itself flutter? Calling the setState() method in a stateful widget in Flutter calls the build() method first. Not only that, the build() method rebuilds all the descendant widgets. To enhance your fluttering performance, you need to understand the inner mechanism of Flutter.
I have been getting this issue on
Flutter 1.22.0 • channel stable
Deleting the app from my emulator/physical phone and reinstalling fixes the issue. Delete the app from the emulator/physical from System Settings/Apps and reinstall in debug mode.
I have no idea why but time to time my main widget keeps on getting rebuild exactly twice and I dont do anything in my main widget no SetStates or no futurebuilder. I think this is a flutter internal bug.
63
The clue might be here
Installing and launching... //We are launching the app , the code bundled with it it's executed briefly before it "sync" to allow hot reload
flutter: ROOT WIDGET //The bundled code executes
Syncing files to device iPhone X... //We start the sync, hot reload triggers an app rebuild
flutter: ROOT WIDGET //The live code executes
If you comment the print, then hot-reload, then uncomment the print, you should only see one "ROOT WIDGET".
32
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
