I have a Flutter Application. Currently I am trying to make an automated integration tests using Test Driver.
This is what I am trying to do.
Scenario:
- Click on Button
- Check if the Progress Dialog appeared
I was wondering if it is somehow possible to get the boolean value of the second step. I was trying to do methods like these:
Future<bool> loadingIndicatorVisible () async {
var a = _driver.waitFor(find.byType("ProgressDialogType.Normal"));
}
but I was not able to do this with mentioned method.
This progress dialog has text "Loading...", but I was not able to do this with find.text either.
Is there any way to do this correctly?
This is something what helped me... I hope that someone in the future will see it useful
isVisible(SerializableFinder finder, {duration = 1}) async {
try {
await _driver.waitFor(finder, timeout: Duration(seconds: duration));
return true;
} catch(exception) {
return false;
}
}
And I used finder which looked like this:
final loadingIndicator = find.text("Loading...");
And of course this is method which I was calling out:
Future<bool> loadingIndicatorVisible () async {
return await isVisible(loadingIndicator);
}
Related
I am trying to execute a function after a dialog is dismissed/popped. I read this article How to run code after showDialog is dismissed in Flutter? and tried to do it as recommended but it wouldn't work for me.
This is how I call my dialog:
Future<void> onDeleteEventData(BuildContext context) async {
final title = context.messages.settings.offline.deleteEventData;
final subTitle = context.messages.settings.offline.deleteEventDataDesc;
final res = await showDeleteDialog(context,
title: title,
subTitle: subTitle);
if (res == true){
context.read<EventDownloadTileController>().deleteEventRelatedData();
}
}
The showDeleteDialog function just calls a custom Dialog which is basically just the Flutter Dialog with some style changes.
Future<bool?> showDeleteDialog(BuildContext context,
{required String title, String? subTitle}) async {
return await showDialog(
context: context,
builder: (_) => DeleteDialog(title: title,subTitle: subTitle,)
);
}
In the dialog I press on a button and do this:
onPressed: () => Navigator.of(context).pop(true),
So looking at the first function I wait for my res which evaluates to true. At this point I thought the dialog should be popped. But it is not.
The problem is this call:
context.read().deleteEventRelatedData();
Because when I replace this call with e.g. Future.delayed(duration(seconds:5)); the dialog pops right away as expected.
This is the function:
Future<void> deleteEventRelatedData() async {
_ticketLoader.stop();
_ticketStorage.deleteScanTicketsForEvent(event.eventId);
_eventStorage.deleteEventPermissions(event.eventId);
_eventStorage.deleteEventData(event.eventId);
_ticketStorage.deleteCachedTicketsForEvent(event.eventId);
_ticketStorage.deleteCachedUnknownTicketsForEvent(event.eventId);
_ticketLoader.updateLastSync(null);
_ticketLoader.reset();
checkLocalStatus();
}
A function with some async and synchronous functions. The execution takes up to 3 seconds which is the time it takes to dismiss/pop my dialog. But I want to pop the dialog right away and let it work in the back. What could my function possibly do for this behavior?
Thanks in advance
The dialog window isn't going to disappear until the app can manage to do a rebuild. If your function call takes a while, it could be hogging the main thread until it's complete, disallowing other code (including widget code) from running.
Try wrapping your function call in a microtask so it doesn't run until the next available task window which will give the app time to clean up the dialog window:
await Future.microtask(deleteEventRelatedData);
It's also worth mentioning the body of the deleteEventRelatedData is marked as async but it never awaits anything. That means all of the synchronous calls can happen in a sequence that wasn't intended and the asynchronous calls won't get executed until a later time and in no guaranteed order.
I have an async function which is called multiple times synchoronusly.
List response = await Future.wait([future, future])
Inside, it popups a form and waiting for it to be submitted or cancelled.
var val = await Navigator.push(
context,
MaterialPageRoute(builder : (context) => const TheForm())
);
The first served Future will popup the form first and waiting for the return. No problem with that. But I want the second Future to check first if the form is already popped up. If it is, it just waiting for it to conclude and receive the same returned value.
I'm aware that receiving same function return from two calls sounds crazy and impossible. I'm just looking for a way to hold the second Future call on and trigger to conclude it from somewhere else.
Kindly tell me what I was missing and I'll provide the required information.
I try to use ValueNotifier's. Unfortunately ValueNotifier.addListener() only accept a VoidCallback. As for now, this is my solution. Still looking for a better way to replace the loop.
Future future() async{
if(ison) await Future.doWhile(() async {
await Future.delayed(Duration(seconds: 1));
return ison;
});
else{
ison = true;
result = ... //Popup form
ison = false;
}
return await result;
}
It sounds like you want to coalesce multiple calls to an asynchronous operation. Make your asynchronous operation cache the Future it returns and make subsequent calls return that Future directly. For example:
Future<Result>? _pending;
Future<Result> foo() {
if (_pending != null) {
return _pending!;
}
Future<Result> doActualWork() async {
// Stuff goes here (such as showing a form).
}
return _pending = doActualWork();
}
Now, no matter how many times you do await foo();, doActualWork() will be executed at most once.
If you instead want to allow doActualWork() to be executed multiple times and just to coalesce concurrent calls, then make doActualWork set _pending = null; immediately before it returns.
My app structure is a little bit mess, but I have to add this patch first and then I'll restructure the entire logic. The thing is I first check if there's a firebase user, then if there is one I use StreamBuilder to get the current user profile from Firestore, then I have the _firebaseMessaging.configure method because onLaunch and onResume I use this callback:
void _navigateToGestorResevas(Map<String, dynamic> message, User currentUser) {
Navigator.push(context,
MaterialPageRoute(builder: (context) =>
GestorScreen(user: currentUser)));
}
Because I need to send the User to this screen where he fetch the message from firebase.
onResume this works fine, but onLaunch it goes to the screen and fetch the data but there are like 20 seconds where there are some kind of glitch. It switch like 20-30 times between two states where I have and no have snapshot data in this _initState func:
final snapshot = await _dbRef.child('mensajes').child(widget.user.id).once();
if (snapshot.value != null) {
setState(() {
hayMensajes = true;
});
final data = snapshot.value;
for (var entry in data.entries) {
Message message = Message.fromJson(entry.value);
setState(() {
message.add(message);
});
}
} else {
setState(() {
hayMensajes = false;
});
}
Anyone have an idea what am I doing wrong?
If I am not mistaken, there are some active issues about FCM onLaunch callback with flutter. Some of them are still not fixed. One of the problems most people had to face was that onLaunch callback being called multiple times. I don't know why it happened, but as in your case, you can possibly get rid of the issue by some temporary fixes.
If the same screen is getting pushed over and over again, and glitching, you can pop the stack until it reaches the one you meant to open and set a condition to push navigator only if the new route is different from the old one. Using the named routes,
Navigator.popUntil(context, ModalRoute.withName(routeName));
if (ModalRoute.of(context).settings.name != routeName) {
Navigator.pushNamed(context, routeName);
}
I am not sure if that was the problem you asked, but I hope at least my answer helps somehow.
What is the difference between Future and Completer?
I am not looking for documentation part on either, instead I would like to see an example showing the real difference between the two.
Completer is a helper class for creating Future whereas Future is a Type.
All asynchronous functions return Future, but with Completer it is possible to create synchronous function that returns Future as well. Also you can chain that synch functions with then etc.
Completer object is one way process, it's not restartable. It does the job and stops.
Future<MyObject> myMethod() {
final completer = Completer();
completer.complete(MyObject());
return completer.future;
}
Update:
To give an example, in one of my projects I had to get the resolution info of network images. To do that, you need something like this:
https://stackoverflow.com/a/44683714/10380182
In there, as you see, after getting the image we do a resolve process which may take time even though it's not an async process. To eliminate that blocking we simply use Completer.
Also the info we need exists inside a callback, so it will be cleaner to use Completer in there. Then, we use it via FutureBuilder. You can approach different but this is very convenient way to handle.
Prefer Future over Completer
A Completer is a class that is used to create a Future from scratch. So unless you really are creating a Future from scratch you probably shouldn't be using a Completer.
How to make a Future
You can create a Future without using a Completer by using the Future's constructor:
final myFuture = Future(() {
final result = doSomethingThatTakesTime();
return result;
});
Using Future.then() is another way to get a Future:
Future<bool> fileContainsBear(String path) {
return File(path).readAsString().then((contents) {
return contents.contains('bear');
});
}
And any async/await method returns a Future:
Future<bool> fileContainsBear(String path) async {
var contents = await File(path).readAsString();
return contents.contains('bear');
}
The above methods are all recommended over using a Completer:
// This is harder to read.
Future<bool> fileContainsBear(String path) {
var completer = Completer<bool>();
File(path).readAsString().then((contents) {
completer.complete(contents.contains('bear'));
});
return completer.future;
}
How to make a Completer
But if you really do need to use a Completer, the way to do it is like this:
Create a new Completer.
Return its future.
Tell the completer either when it is complete or when there is an error.
Here is an example:
class AsyncOperation {
Completer _completer = new Completer();
Future<T> doOperation() {
_startOperation();
return _completer.future; // Send future object back to client.
}
// Something calls this when the value is ready.
void _finishOperation(T result) {
_completer.complete(result);
}
// If something goes wrong, call this.
void _errorHappened(error) {
_completer.completeError(error);
}
}
The code in this answer comes from the documentation and from the Effective Dart guide.
I'm developing a Flutter app which has some tabs inside, each of them depend on the database that is loaded on the first run. State is stored in a ScopedModel.
On every tab I have this code:
#override
void initState() {
super.initState();
loadData();
}
void loadData() async {
await MyModel.of(context).scopedLoadData();
_onCall = MyModel.of(context).onCall;
setState(() {
});
}
And this is the code snippet that matters for the ScopedModel:
Future<Null> scopedLoadData() async {
if (_isLoading) return;
_isLoading = true;
(...)
_isLoading = false;
}
If the user waits on the first tab for a few seconds everything is fine, since Database is loaded. However, if the user switches tabs right after app launch, the method scopedLoadData is still being executed so that I get a runtime error ("Unhandled Exception: NoSuchMethodError: The method 'ancestorWidgetOfExactType' was called on null.").
This exception happens because the scopedLoadData has not yet been completed. So I'm looking for a way to wait for a method that is still being executed.
Thanks!
Not sure without seeing your build method but I would start your build method with a guard clause.
if (_oncall == null) return Container(); // or Text("loading") or similar
use should be using a FutureBuilder on each tab to make sure the data is loaded before you try to build the widget... more code would be helpful
I solved the exception by getting rid of every:
setState(() { });
and implementing ScopedModelDescendant on every relevant tab on top of using notifyListeners() at the end of the database loading method.
This pulls the responsibility from the tabs for updating views and gives it to the scopedLoadData().