I am getting a crash on some android devices when running my Flutter app.
I have been able to debug a release version of the app and this is the only debug output:
W/FlutterJNI(27448): FlutterJNI.loadLibrary called more than once
W/FlutterJNI(27448): FlutterJNI.prefetchDefaultFontManager called more than once
W/FlutterJNI(27448): FlutterJNI.init called more than once
I don´t know where should I begin to look for the reason of the issue.
The device is showing a gray screen and stops working.
Wherever you create the firebaseMessagingBackgroundHandler, annotate it with #pragma('vm:entry-point') like this:
#pragma('vm:entry-point')
Future<void> firebaseMessagingBackgroundHandler(RemoteMessage message) async {
}
The reason is explained here:
https://github.com/firebase/flutterfire/blob/master/packages/firebase_messaging/firebase_messaging/example/lib/main.dart#L46
How do I put imageCache.clear(); into my Flutter app? Five of my six images are loading but one refusing to load. I tried flutter clean and restarting Android Studio. When I do this at the top of the program:
import 'package:flutter/material.dart';
imageCache.clear();
I get this error message:
lib/main.dart:2:19: Error: Expected a function body or '=>'.
Try adding {}.
imageCache.clear();
I tried this
imageCache.clear() {}
but that got a different error message.
You probably put the function in the wrong place.
You can put in the initState
void initState() {
super.initState();
imageCache.clear();
}
or wherever a function should be not where a widget should be.
I want to clear shared preferences when I send a FCM message and app is in background. Inside myBackgroundMessageHandler method I am calling a method to clear them.
static Future<dynamic> myBackgroundMessageHandler(
Map<String, dynamic> message) {
clearPreferences();
}
static void clearPreferences() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.clear();
}
I am getting the following error:
Unhandled Exception: MissingPluginException(No implementation found
for method getAll on channel plugins.flutter.io/shared_preferences)
step 1)
go to Application.kt/Application.java (in my case is kotlin)
step 2)
add these line into Application class (in kotlin)
if (!registry!!.hasPlugin("io.flutter.plugins.sharedpreferences")) {
SharedPreferencesPlugin.registerWith(registry!!.registrarFor("io.flutter.plugins.sharedpreferences.SharedPreferencesPlugin"));
}
remember import this as well
import io.flutter.plugins.sharedpreferences.SharedPreferencesPlugin
step 3)
run flutter clean -> flutter get -> uninstall your app
The code is completely fine.
Just restart your emulator. If you didn't do a full restart by closing the emulator and open it up again, this error can propably occur, because it doesnt have the newly added plugins.
Add SharedPreferences.setMockInitialValues({}) to your code before the runApp() function inside the main function of Flutter App.
this fixed the error for me
I'm writing tests for a mobile App written in Flutter.
I followed this Flutter Cookbook on testing Flutter apps, to learn how to write widget and integration tests.
This tutorial works perfectly, but I'm still stuck with my own Integration tests.
To simplify, let's assume I have an app, containing only a TextField:
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'MyAppp',
home: Scaffold(
body: Center(child: TextField()),
),
);
}
}
I want to write a test for this app. For instance, I want to test the following scenario:
Open the app
Check that the TextField is empty
Select the TextField
Enter "hello, world!"
Check that TextField contains "hello, world!"
I wrote the following Widget test, which works fine:
void main() {
testWidgets('TextField behavior', (WidgetTester tester) async {
// Create app
await tester.pumpWidget(MyApp());
// Find TextField, check there is 1
final textFieldFinder = find.byType(TextField);
expect(textFieldFinder, findsOneWidget);
// Retrieve TextField Widget from Finder
TextField textField = tester.widget(textFieldFinder);
// Check TextField is empty
expect(textField.controller.text, equals(""));
// Enter text
await tester.enterText(textFieldFinder, "hello, world!");
// Check TextField contains text
expect(textField.controller.text, equals("hello, world!"));
});
}
This test passes, but I wanted to write an Integration test, doing more or less the same, to be able to test it on a real device.
Indeed if this Widget test passes, it will probably pass on all device. But in my app I have more complex widgets and interactions between them, I want to be able to launch tests on both Android and iOS.
I tried to write integration tests using Flutter driver, but I did not find what I wanted in the documentation and examples.
How can I check Widget properties, to verify that my App behaves as expected?
I wrote the following sample:
import 'package:flutter_driver/flutter_driver.dart';
import 'package:test/test.dart';
void main() {
group('TextField', () {
final textFieldFinder = find.byType('TextField');
FlutterDriver driver;
setUpAll(() async {
driver = await FlutterDriver.connect();
});
tearDownAll(() async {
if (driver != null) {
driver.close();
}
});
test('TextField behavior', () async {
// ??? how to check that the TextField is empty
await driver.tap(textFieldFinder);
await driver.enterText("hello, world!");
// ??? how to check that the TextField contains hello, world!
});
});
}
The Flutter Cookbook tutorial explains how to retrieve an object by its Text, this would help to check if the Text is present, but for instance is it possible to check that a Container color is red?
Where is the limit between Widget and Integration tests?
Writing Widget tests is pretty straighforward, but I didn't find many examples or documentation about how to write more complexe integration tests using Flutter driver.
If anyone is interested:
To be able to test what I want (not only the presence of widgets, but also theirs states, their properties,...) test driver was not enough for me.
What I did in my project, is to use the flutter_test to write widget tests and check the properties I want.
To test it on a real device (Android or iOS), I used the integration_test package (previously e2e package) available here, which adapts flutter_test results to a format compatible with flutter drive.
To use integration_test, add this line in the main of your widget tests:
IntegrationTestWidgetsFlutterBinding.ensureInitialized();
Then create a file (e.g. integration_test.dart) in your test_driver folder with this content:
import 'package:integration_test/integration_test_driver.dart';
Future<void> main() => integrationDriver();
Then you can launch these driver test by running:
flutter drive \
--driver=test_driver/integration_test.dart \
--target=test/widget_test/widget_test.dart
With your widgets tests wrote in the file test/widget_test/widget_test.dart.
It really helped me, since some widgets did not have the same behavior on Android and iOS.
Today I use both flutter_test (launched on real device with integration_test) and real flutter_driver tests:
I write widget tests to check a single widget, or a single page,
I use flutter driver to write more sophisticated scenarios to test the whole application.
I think there's a difference between flutter widget and flutter driver. In that, flutter widgets is for widget tests and flutter driver is for integration tests. I'm not exactly sure what that means on a practical standpoint but I think integration test are easier to run tests on application interactions that would be made by a user since integration tests run on an actual device as compared to widget tests. Will update if I find more information on this.
I am trying to force my Flutter app to only use Portrait mode. My main() method looks like this.
void main() {
SystemChrome.setSystemUIOverlayStyle(uiOverlayStyle);
SystemChrome.setPreferredOrientations(ALLOWED_ORIENTATIONS)
.then((_) => runApp(MyApp()));
}
Here is the definition of ALLOWED_ORIENTATIONS:
const List<DeviceOrientation> ALLOWED_ORIENTATIONS = [
DeviceOrientation.portraitUp
];
I just separated all the settings and such to another file to make modifying them later on easier.
When I run this code, I get the following error.
[VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception:
ServicesBinding.defaultBinaryMessenger was accessed before the binding was initialized.
If you're running an application and need to access the binary messenger before `runApp()`
has been called (for example, during plugin initialization), then you need to explicitly
call the `WidgetsFlutterBinding.ensureInitialized()` first.
It looks like there is some race condition that's failing. I am just not sure what is causing it. Removing the SystemChrome.setPreferredOrientations() line makes the app compile as expected. So, I am thinking the error has something to do with that line.
Any advice?
Like the error says
If you're running an application and need to access the binary
messenger before runApp() has been called (for example, during
plugin initialization), then you need to explicitly call the
WidgetsFlutterBinding.ensureInitialized() first.
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setSystemUIOverlayStyle(uiOverlayStyle);
await SystemChrome.setPreferredOrientations(ALLOWED_ORIENTATIONS);
runApp(MyApp());
}