In a interview someone asked me this question. Suppose there are 4 activities in application. He wants back button to work normally on first three activities(i.e. going to previous screen on back button press); except the last.
He wanted that, when he press back button on fourth activity(screen), user should go to Home Activity(Starting Screen or first screen). But the contents on Home Activity should be same when user went from first screen to second screen. So I think, I can't use Intent, as it will create new instance of Starting Activity.
He wanted that, when he press back button on last activity(screen), user should go to Home Activity(Starting Screen or first screen).
The interviewer should be interviewing for his or her own replacement, if (s)he thinks that hacking the BACK button this way is a good idea.
So I think, I can't use Intent, as it will create new instance of Starting Activity.
Add FLAG_ACTIVITY_REORDER_TO_FRONT or the combination of FLAG_ACTIVITY_CLEAR_TOP and FLAG_ACTIVITY_SINGLE_TOP to the Intent used with startActivity() to bring up your "home activity". Either will cause the existing "home activity" instance to come to the foreground. If you want all other activities to be destroyed, use the second approach (FLAG_ACTIVITY_CLEAR_TOP and FLAG_ACTIVITY_SINGLE_TOP).
Related
So I would like to know how I can manage the back stack for activities that are launched from the NavigationDrawer. If I launch various activities via the NavigationDrawer by default Android will add them to the back stack and it would cause back button hell as user.
I imagine this should be a common problem so there must be a adequate solution.
But I need a solution to cater for the following 3 requirements.
Requirement 1)
I have 2 items in the navigation drawer (Activity1 and Activity2) which each launch different Activites. If I open the items via the navigation drawer a number of times when I press back I wish to go back to the initial starting activity and if I press back again I wish to exit the app
Requirement 2)
I launch Activity 1 from Nav then I launch Activity 2 and from within this activity I launch a new activity SubActivity. Now when I press back I would expect to be taken back to Activity 2 and then if I press back again I would expect to be taken to the initial Activity (not Activity 1), and then pressing back again would exit.
Requirement 3)
Same as above but actually the initial Activity is dynamic. So the landing Activity is defined by a user setting about what their first screen shall be.
As you can see I can not use NO_HISTORY flag because of (requirement 2)and I cant hardcode the parent of the Activities because of (requirement 3).
So other than overriding the back button is there any other way that i can manipulate the back stack ?
Thanks
Launch mode will not help. The answers lies in using TaskStackBuilder, its a very powerful api that allows you to define exactly what is to go into the backstack of the activity that you are about to launch. Here is how to use it.
Intent activityInBackstack = new Intent(this, ActivityA.class);
Intent activityToBeLaunched = new Intent(this, ActivityB.class);
TaskStackBuilder builder = TaskStackBuilder.create(this);
builder.addNextIntent(activityInBackstack);
builder.addNextIntent(activityToBeLaunched);
builder.startActivities();
So now if you are in ActivityB and you press back button you will always go to ActivityA. Pressing back on ActivityA would exit the app.
The official Dev Guide of Tasks and Back Stack says, activities can be instantiated multiple times, and Home Activity is taken as an example
So I tried it out as the graph illustrates:
Launch Activity 2
Press Home button
Launch Activity 1
Press Back button (so I return to Home screen)
Press Back button again
But I did not go back to Activity 1. Thus, it seems that Home Activity has not been instantiated multiple times. Is it so? If so, how is it kept in a Back Stack?
EDIT: Sorry, I should've clarified earlier that I didn't write any codes to test it. All I've done is just launching applications on favorites tray. I'd better go to read the source code and search for the behavior of Home Activity.
Anyway, I don't think Home Activity is a good example here to illustrate multiple instances.
Your issue might be that you might have called finish() in your Activity2. Or, the OS clears up the 2nd Activity before you return back to it. The behavior you are trying to attain on your own has no guarantees. You can't force an Activity to keep running so that you can return back to it.
I am trying to close a whole stack of activities using the way described here:
How to kill an application with all its activities?
Namely, each activity starts the other one with startActivityForResult, and in onActivityResult calls finish() to close itself together with the activity it opened.
The problem is that the activities in the task still seem to repaint themselves at least once before they close, and this doesn't look good. After closing the topmost activity one sees all previously opened activities like in a very fast slideshow.
How can one avoid this graphical issue?
EDIT: I need that if the user presses HOME button and then presses the app's icon in launcher, he returns to the current state of the stack, not to the very first activity again. So, from what I understand, with such a requirement I can't finish() activities before starting next ones.
That's native behaviour, intended to aid in user Experience. When an Activity is started with startActivityForResult and then finishes, it will (on devices that allow fancy animations) automatically slide away. That helps people not get surprised by the screen suddenly changing.
You could try starting the Activities without startActivityForResult and handling the passing of data to and from Activities manually, then handle how/when Activities finish() and which Activity they pass back to. You might find you implement something where Activities actually pass forward to the appropriate Activity all the time, rather than back to an Activity on the stack.
Intent intent = new Intent();
intent.setClass(getApplicationContext(),
PhoneListCheckboxAES.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
finish();
If u give like this when u are starting the next activity then the graphical problems won't occur
I have not really understood the handling of activities and the stack.
I have 3 activities, A - a splashcreen, B- a menu and C another Activity. I start the splash and exits it after a while when the menu is started.
In code I handle them all like this:
startActivity(new Intent(this, ContactInfoMenu.class));
finish();
Now, if I start the app and goes A-B-C, when I hit "Back" in C screen I jump back to B-the menu. Another "Back" exits the application, just like I want.
BUT .. if I go A-B-C-B-C - the "Back" button in C screen exits the whole app instead of getting me back to the B screen?
Why is that? It does like that in all my "subscreens", I can only enter them once, if I enter them a second time the "Back" button exits the app. And I have not tried to catch the "Back" action anywhere? Shouldn't I always call "finish()" when I start a new activity?
Regards
Finish is good for leaving the current activity and going back to the previous one. Otherwise, try to avoid calling finish() if you can help it.
There are a set of flags that you can pass when you start an activity that do a better job of determining how that activity behaves on the stack. These include:
FLAG_ACTIVITY_NO_HISTORY - your activity will not remain on the stack after another activity covers it.
FLAG_ACTIVITY_CLEAR_TOP - a good way to pop off a bunch of activities when you need to "go back" to a certain activity.
Many of these flags can be set in the manifest. Reading up on them will give you a better idea about "The Android Way".
Basically, You don't need to call finish() every time you go to another activity. If system is low on memory it will close your activity instance by itself.
finish() is more often used when yor are inserting some information in one page and then moving on to some other page. In that case, you might need to fininsh your first activity.
But in case where you need to shuffle between views, you must not use a finish() function, because it will cause the whole application to finish.
Try using back button of your own in your views to shift between activities, where you can move to any other activity of your application or even to the Main Screen.
Hi I'm writing an app that has multiple activities. Right now it starts at the home screen, then when the user presses a button it starts a new activity and goes to another screen, then the user enters in information and presses a button to start another activity and another screen.
I have a menu setup so that from whatever the activity the user is in they can get back to the home screen. What I want it to do is kill all the current activities and just take the user right back to the home screen, so there is only one activity running again. How can I do this?
After sending the Intent just call finish() and the activity you're leaving will be closed.
Just don't do that on your "homescreen" activity. That way whenever the user starts an activity through one of your activities when he presses the back hardware button he is going to get back to your "homescreen" activity.
I figured it out. If you add myIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); then when you run startActivity(myIntent); it clears all activities except the one myIntent is starting.