I have a fragment with UI that is responsible for doing short async api-calls. When an async task completes fragment triggers a Toast message with a result-string.
My issue is that if a user presses Back button without waiting for the result the app crushes due to a onPostExecute method, which in turn triggers Toast + getString(R.string.whatever) in the fragment that is already detached, because the activity is behind the onDestroy state.
I can check whether the fragment is detached or use a ProgressDialog, which is modal but I think it would be nice to show the toasts without blocking or any other quirks. Any suggestions on how to achieve it? Broadcast receiver in the application class == overkill?
Thanks.
UPD logs:
01-24 12:01:29.626: E/AndroidRuntime(616):
java.lang.IllegalStateException: Fragment
HandsetSocialNetworksFragment{40612a78} not attached to Activity 01-24
12:01:29.626: E/AndroidRuntime(616): at
android.support.v4.app.Fragment.getResources(Fragment.java:571) 01-24
12:01:29.626: E/AndroidRuntime(616): at
android.support.v4.app.Fragment.getString(Fragment.java:593)
At the start of the async call, get the activity from the fragment, and get the application context from it. Use that one later to get the string you need.
Alternatively, you can fetch the string you need when you start the async call, instead of when you have to show the toast.
Related
I have came across a requirement where i want axon to wait untill all events in the eventbus fired against a particular Command finishes their execution. I will the brief the scenario:
I have a RestController which fires below command to create an application entity:
#RestController
class myController{
#PostMapping("/create")
#ResponseBody
public String create(
org.axonframework.commandhandling.gateway.CommandGateway.sendAndWait(new CreateApplicationCommand());
System.out.println(“in myController:: after sending CreateApplicationCommand”);
}
}
This command is being handled in the Aggregate, The Aggregate class is annotated with org.axonframework.spring.stereotype.Aggregate:
#Aggregate
class MyAggregate{
#CommandHandler //org.axonframework.commandhandling.CommandHandler
private MyAggregate(CreateApplicationCommand command) {
org.axonframework.modelling.command.AggregateLifecycle.apply(new AppCreatedEvent());
System.out.println(“in MyAggregate:: after firing AppCreatedEvent”);
}
#EventSourcingHandler //org.axonframework.eventsourcing.EventSourcingHandler
private void on(AppCreatedEvent appCreatedEvent) {
// Updates the state of the aggregate
this.id = appCreatedEvent.getId();
this.name = appCreatedEvent.getName();
System.out.println(“in MyAggregate:: after updating state”);
}
}
The AppCreatedEvent is handled at 2 places:
In the Aggregate itself, as we can see above.
In the projection class as below:
#EventHandler //org.axonframework.eventhandling.EventHandler
void on(AppCreatedEvent appCreatedEvent){
// persists into database
System.out.println(“in Projection:: after saving into database”);
}
The problem here is after catching the event at first place(i.e., inside aggregate) the call gets returned to myController.
i.e. The output here is:
in MyAggregate:: after firing AppCreatedEvent
in MyAggregate:: after updating state
in myController:: after sending CreateApplicationCommand
in Projection:: after saving into database
The output which i want is:
in MyAggregate:: after firing AppCreatedEvent
in MyAggregate:: after updating state
in Projection:: after saving into database
in myController:: after sending CreateApplicationCommand
In simple words, i want axon to wait untill all events triggered against a particular command are executed completely and then return to the class which triggered the command.
After searching on the forum i got to know that all sendAndWait does is wait until the handling of the command and publication of the events is finalized, and then i tired with Reactor Extension as well using below but got same results: org.axonframework.extensions.reactor.commandhandling.gateway.ReactorCommandGateway.send(new CreateApplicationCommand()).block();
Can someone please help me out.
Thanks in advance.
What would be best in your situation, #rohit, is to embrace the fact you are using an eventually consistent solution here. Thus, Command Handling is entirely separate from Event Handling, making the Query Models you create eventually consistent with the Command Model (your aggregates). Therefore, you wouldn't necessarily wait for the events exactly but react when the Query Model is present.
Embracing this comes down to building your application such that "yeah, I know my response might not be up to date now, but it might be somewhere in the near future." It is thus recommended to subscribe to the result you are interested in after or before the fact you have dispatched a command.
For example, you could see this as using WebSockets with the STOMP protocol, or you could tap into Project Reactor and use the Flux result type to receive the results as they go.
From your description, I assume you or your business have decided that the UI component should react in the (old-fashioned) synchronous way. There's nothing wrong with that, but it will bite your *ss when it comes to using something inherently eventually consistent like CQRS. You can, however, spoof the fact you are synchronous in your front-end, if you will.
To achieve this, I would recommend using Axon's Subscription Query to subscribe to the query model you know will be updated by the command you will send.
In pseudo-code, that would look a little bit like this:
public Result mySynchronousCall(String identifier) {
// Subscribe to the updates to come
SubscriptionQueryResult<Result> result = QueryGateway.subscriptionQuery(...);
// Issue command to update
CommandGateway.send(...);
// Wait on the Flux for the first result, and then close it
return result.updates()
.next()
.map(...)
.timeout(...)
.doFinally(it -> result.close());
}
You could see this being done in this sample WebFluxRest class, by the way.
Note that you are essentially closing the door to the front-end to tap into the asynchronous goodness by doing this. It'll work and allow you to wait for the result to be there as soon as it is there, but you'll lose some flexibility.
I have a Command that executes a service call. In the result handler, I am doing some logic based off the result data. If the logic meets specific criteria, I am displaying a confirmation popup. If the user clicks the continue button in the confirmation popup, I have a method that gets called, which dispatches a Parsley event. That Parsley event is not being caught. However, if I dispatch the Parsley event from inside the result method, it is being caught. Any idea why the event is not being caught when dispatching it from outside the result method?
For example...
[MessageDispatcher]
[Bindable]
public var dispatcher:Function;
I execute some service call from inside the command:
public function execute(event:SomeEvent):AsyncToken
{
return service.callService(event.type, false);
}
I now have a result handler like this:
public function result(data:Object):void
{
if (add some logic here based off data)
AlertHelper.showContinueQuestion(onSelection, "Are you sure you want to continue?");
}
If the user clicks the Continue button on the confirmation popup, it calls the onSelection method:
private function onSelection():void
{
dispatcher(new SomeEvent(SomeEvent.UPLOAD));
}
That Parsley event, SomeEvent, is not being caught. However, if I dispatch that event after the if statement, it is being caught and works fine. Any idea why it is not being caught when dispatched from outside of the result handler? I tried in other commands too, and it does the same thing.
Found this on the Spicefactory site, works as designed. I ended up updating a flag in the Model, versus dispatching an event. I then have a BindSetter listening for changes to that flag in the model. When the flag is set to true, the Parsley event is dispatched.
Command Object Lifecycle
Apart from grouping the executing method and the result handlers the DynamicCommand also introduces a special kind of lifecycle management for command objects. The creation of the object does not happen until a matching message is dispatched. It then becomes a container managed object just for the duration of the command execution. It will immediately be removed from the Context after the result or error handler have been invoked. But during its lifetime, it is a fully managed object, can have its dependencies injected, or even take part in messaging during the command execution. But that would be a rather rare case, most common usage scenario is probably the command object just receiving all the dependencies it needs to execute the command.
I'm using the SDL Tridion event system to fire a method (OnEmergencyRelease) once a Workflow Activity has been completed. However my method isn't being entered during testing, where I'm stepping some components through the workflow process.
I'm subscribing using the following code:
EventSystem.Subscribe<Component,
FinishProcessEventArgs>(OnEmergencyRelease, EventPhases.TransactionCommitted);
But OnEmergency is never being entered:
private void OnEmergencyRelease(Component component,
FinishProcessEventArgs args, EventPhases phase)
{
_log.Info("Emergency release entered");
}
Anyone have any ideas what I'm doing wrong here?
I know the event system is being picked up as I write to the log in the constructor of my class.
I can't tell you for sure what happens, but I suspect that the FinishProcessEventArgs is not called on the Component object itself. Maybe you should try intercept on an object 'higher up' in the class hierarchy.
Example: use Process (or ProcessInstance or even IdentifiableObject)
EventSystem.Subscribe<Process, FinishProcessEventArgs>(OnEmergencyRelease, EventPhases.TransactionCommitted);
Is the event firing? I would expect Finish Process events to fire when you explicitly invoke a finish process action, and probably not when you step the items through.
I subclass NSOperation to implement my operation.Let's call it MyOperation.
In the implementation of MyOperation, I override the main function and inside it I create some async network stuff and set the delegate to self(the operation object).But the operation objects never get those delegate callbacks, why? I didn't set finished before the callback are received.
Or does NSOperation just can't do that?
I find that if I manually "start" the operation, it will work. But if I add it to a operation queue, the operation is excuted but just can't get those callbacks.
If you're setting up your callback in the main method like this:
-(void)main{
// setup
object.delegate = self
}
then your main method will continue execution, complete, and go away before the delegate has a chance to complete the callback. You either need to override the start method in NSOperation and manually handle the isFinished and isExecuting properties, or you need to figure out a way to have the delegate method get called on an object that isn't going away.
See the NSOperation class reference for full details on overriding the proper methods and KVC notifications to make it work.
I need to call FileReference.save() after a web service call has completed, but this method has a restriction: "In Flash Player, you can only call this method successfully in response to a user event (for example, in an event handler for a mouse click or keypress event). Otherwise, calling this method results in Flash Player throwing an Error exception." (from the documentation here)
This restriction is a bit vague. Does it mean that I can only call the FileReference.save() method from within an event handler function that is registered as a listener for certain types of user events? If so then exactly which user events are valid? (Perhaps there's an event that will never be dispatched by user interaction with my application and I could register an event handler function for that event type and make the save() call from within that function?)
My difficulty is that I can't safely call the FileReference.save() method until my web service returns with the data that will be used as the argument of the FileReference.save() method call, so the event that triggers the FileReference.save() call is actually a ResultEvent rather than a user event, and I'm leery of dispatching a new (faux) user event type in order to be able to trigger the FileReference.save() call unless it's definitely a user event that would never be dispatched as a result of actual user interaction with my application.
In a nutshell what I'm doing now is this: I have a function that is registered as a handler for a button click. In this function I make my web service call to fetch data from the server. I also have a result handler function which gets invoked when the web service call completes, and it's in here that I want to call the FileReference.save() method since it's at this point that I know that the data is ready to be saved to a file. But the aforementioned restriction is blocking me from doing this -- I get an error:
Error #2176: Certain actions, such as those that display a pop-up window,
may only be invoked upon user interaction, for example by a mouse click
or button press.
I've tried many things to get around this such as creating a second mouse click event handler function with the FileReference.save() call within and calling it after a timeout interval (to give the web service time to complete), but I keep running into the same error -- maybe that approach doesn't work since the second function isn't registered as an event listener for the event type used as its argument.
I'm new to Flex development so perhaps I'm just not thinking about this in the right way. If anyone can suggest another approach I'd really appreciate it. Thanks in advance for your comments or suggestions.
--James
Adobe does this as a sort of security measure to ensure users are the ones messing with files rather than potentially harmful code. My understanding is that they enforce this by only allowing handlers of (click?) events that originate from UI components to execute the FileReference methods, so generating your own events programmatically will not work, although I have not tried to verify this. Unfortunately the best resolution I've found is to re-work the UI a bit to conform to this constraint. In your particular situation, you could make this a two click process with a button that says something like "Prepare Download", which changes to "Download File" after the web service is complete. This is less than ideal from a user perspective, but I don't think there's much else that can be done unless you can somehow complete your web service call prior to displaying the button that triggers the FileReference.save() call.
After struggling for that for well, a couple hours I found a workaround: you can use both mouseDown AND mouseUp events instead of just click.
For instance:
s:Button
mouseDown="prepare_PDF()"
mouseUp="save_PDF()"
Works fine for me!
Happy coding!
--Thomas
As a workaround I used the ExternalInterface class. I created a javascript function with this code
function downloadFile (url) {
window.open(url);
}
An in AS3 I call
var url = 'www.example.com/downloadfile.php?file_id=xxx';
ExternalInterface.call('downloadAttachmentFile', url);
So with that I transfer the file handling to JS/HTML.
This is a comment on Thomas' answer (I don't have enough XP to comment yet): The mousedown and mouseup workaround works nicely. Just a note that if you make any changes in prepare_PDF() that need 'undoing' in save_PDF(), then its a good idea to call that code on the mouseout event as well, since there might be a case that the user mousedown's on the button, but then moves the mouse away from the button.
This was particularly relevant for my case, in which we increase the size of a watermark on an image when the user clicks the download button (that triggers the .save() call). I reduce the size of the watermark down to normal on the mousedown and mouseout events.
I had this same issue, I chose to use flash.net methods. Call flash.net.navigateToURL(url); from an actionscript or navigateToURL(url); from mxml.
What i do to solve this is to show an alert message with an anonymous function so i don't have to create a button.
Alert.show("Do you wish to download the file?", "Confirm", Alert.OK | Alert.CANCEL, this, function (eventObj:CloseEvent):void {
if (eventObj.detail == Alert.OK) {
fileReference.save(zipOut.byteArray, dateFormater_titulo.format(new Date ()) + ".zip");
}//if
}/*function*/, null, Alert.OK);