I'm using a singleTask-mode activity that handles a certain type of files by specifying a intent-filters.
I need to handle each such file Intent exactly once. The problem is onNewIntent() is only called if the task is already alive, forcing me to handle the intent from onCreate() too. Unfortunately, onCreate() gets called for a whole bunch of reasons (e.g. screen rotation), and the Intent returned by getIntent() may be the same one across several onCreate()'s.
Of course, it is possible to work-around this using some ugly hack, but I was wondering what the elegant solution would be.
So far the best solution I came up with is to setIntent(new Intent(Intent.ACTION_MAIN)) every time after handling an intent. This is a similar pattern to how web servers redirect you to a GET page after a POST page to avoid redoing an operation as result of refresh.
Thanks!
I am not sure If I get your Problem, but once you call an intent and start the new activity,
immediately after call finish(); to end the activity you are leaving. This will end your last activity and will prevent from multiple activities from running at the same time.
Also if you are using screen rotation as a way to launch activities, you can always control which one's you do not want to start multiple times by setting some checks using "If and Else" Statements.
remove singleTask will solve your problem;
call remove singleTask's activity, can replace with:
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP
| Intent.FLAG_ACTIVITY_SINGLE_TOP);
How about setIntent(null) after handling it?
Related
I'm designing an app composed two activities. The first one always run, and is asked to trigger a second one when some stuff happens. This works fine with the standard code used for running activities:
Intent myIntent = new Intent(this, allarme.class);
myIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(myIntent);
however, the activity in allarme.class is not started if i'm using another app (i.e. gmail),
whilel it works perfectly from home or when the screen is locked.
I'm sure that the first activity is still running, it's just that the second action is not triggered.
Should I change anything in the manifest file to fix this?
I'm not really clear about what you want.
but I guess you want to run two activities simultaneously, am I right?
while one activity run in background and one activity update the UI.
always keep in mind that Android architecture only allowed one activity to run at the time. If you want to pass the data from Asynchronous Task, you can call the method from that class and let your handler 'recent' class update the UI.
You can create a background service that always run at background even if you are using another app or phone is locked. Here is link for more help :
http://developer.android.com/training/run-background-service/create-service.html
Thanks everybody, I think I solved it.
Basically, I found out that an activity already running can be brought to focus when re-started with a basic startActivity. Then I can immediatley switch to the new activity without losing the focus.
When the user clicks a button in my application, it will alter some data in the document being worked on and at that point I want the activity to rebuild its UI. I want to do it this way if possible because exactly what views need to be updated for any given change is going to be tricky to know in advance.
I tried getting the intent, calling finish() on the activity then calling StartActivity with the same intent. Using this method I can disable all the pending transitions, so it's fine except because it creates a new instance of the activity its state can't be recovered (unless I do something really dumb like save it to preferences). And this is not acceptable because the activity contains a ViewPager which using this method returns to page 0 whenever I update something.
Next I tried using Activity.Recreate(). This solves the issue around the state not being saved since it appears to be the same instance of the activity. But in this case I can't work out how to disable all the animations, so there is always a flash on screen.
Is there a way I can make an activity.recreate() call look seamless to the user? Or is there a better way? Since this is all within a viewpager, refreshing the fragment would work just as well, but this not happening from the fragment class itself, but rather many objects which each provide part of the UI.
I faced similar problem, when I invoked recreate on activity it was blinking, I ended up using below code:
// uncomment below line for blink effect :P
// recreate();
// restart activity without blinking :-)
Intent intent = new Intent(MyActivity.this, MyActivity.class);
startActivity(intent); // start same activity
finish(); // destroy older activity
overridePendingTransition(0, 0); // this is important for seamless transition
I know I am too late to answer your question but I hope that it will help other developers who are facing same problem.
What to do when:
1. The app uses a complex structure of Activities and Fragments
2. I return to a backgrounded application that has been (partially or not) destroyed in the meantime
3. It returns me to the last screen, which lies deep in the workflow
4. I need it to return to the first screen to reinitialize things (because it's complex and requires user interaction)
Just to be clear:
I am asking how to deal with the existing stack(s) of Activities and Fragments upon encountering this situation.
- action to take: launch an Intent? Just finish? Do something to held substructures and then finish?
- when to perform it - immediately in both Activity.onCreate and Fragment's empty constructor? Or are Activities sufficient?
- How best to detect it: all I've come up with so far is: binding to a Service that holds the necessary data/connection, and then asking if it's been initialized. But the binding finishes AFTER onResume.
I am not asking about anything UI-related.
I am not asking for a solution that will only work for one specific application, so don't ask for code.
If you see this question as vague, here is a one-sentence version: "How to dismiss the stack and return to the first screen?"
For details (as much, at least, as are relevant), see https://stackoverflow.com/questions/14650342.
If you recognize that your application is in an inconsistent state and you need to start over, the easiest way is to relaunch your root activity like this:
Intent intent = new Intent(this, MyRootActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
finish();
This will clear all activities from the task and restart the root activity.
I would suggest doing this in onCreate() of activities.
when app is in the background and os wants to free some memory. whole PID is killed, which kills ALL activities. Docs are misleading about this behaviour. See this post
Android app out of memory issues - tried everything and still at a loss
where hackbod (Android platform developer) kind of confirms it.
When you have mulitple activities A,B,C and when your app is killed and you want to bring it back.
onCreate(not null) of most top activity will be called. Its worth noticing that when this scenario happens and you do something like
onCreate(not null){
startActivity(new intent)
finish;
two things will happen :
startActivity will launch new activity
finish will close current activity BUT it will bring back the previous activity (from killed pid) with its onCreate(not null) which simply was next activity in the activity stack.
This might cause multiple activity instances problems.
I had a similar problem some time ago, ended up with ugly hack but it worked :
to reinit whole app, I added something like
onCreate(not null){
if(launcher activity == null){
finish();
return;
in all activities.
Depending on what you want to achieve use flags as others have suggested.
Hope that gives you some hints.
If your goal is to dismiss all the activities and get back to your home/main activity then you can simply use:
Intent intent = new Intent(getApplicationContext(), Home.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
This will clear all the activities on top of home and return you to the home screen.
I have an app that will never require more than one instance of an activity. I want it so that when the user comes back to a screen it is in the same state as they left it except for a few places where it doesn't make sense. I've worked out saving the persisted data with onpause onstop updates. However to keep the screen looking the way it did when they left it i use intents specifically setting the flags to Intent.FLAG_ACTIVITY_REORDER_TO_FRONT|Intent.FLAG_ACTIVITY_SINGLE_TOP then startActivity. It seems to work great but does it make sense? Is there a smarter way? Pitfalls doing it this way etc... any feedback will be greatly appreciated.
android:launchMode = "singleTask"
add the above line for every activity in the manifeast file. Adding these launch relaunch the activity instead of creating the activity again.
Refer this link
Newbie question... So I have two activities, Cherry and Apple, and each one has a button on it to go to the other one. So back and forth.
In class "Cherry" I say this:
intent = new Intent(Cherry.this, Apple.class)
startActivity(intent);
Meaning that it should go to the Apple. There's similar code in the Apple activity.
What I think I am seeing is, is that each time when I startActivity Apple for example, it's starting a new instance of it instead of just reactivating Apple. I've scoured the doc and can't find the flag or other call that would do what I want.
Any tips would be appreciated!
-- Pito
What about FLAG_ACTIVITY_REORDER_TO_FRONT?
FLAG_ACTIVITY_CLEAR_TOP is also quite useful, finishing activities on the back stack until the target activity is reached.
To be clear, your activity may be restarted even if using the flags above. This would happen if your activity were destroyed in an attempt to free memory. In other words, you still need to make sure your activity can handle being restarted, taking the proper precautions in onPause and onSaveInstanceState.
Intent.FLAG_ACTIVITY_REORDER_TO_FRONT will bring the launched activity back to front if it's already running as given here. You will have to handle the back button yourself so as not to finish the current activity.