I have a navigational bar (a bunch of buttons) in a fragment and I'm trying to have it on every page of my app.
When I interact with the homepage and change the text to abc on a button and then click the navigational bar fragment, I am successfully taken to the next page. When I hit android's given back button, the app successfully moves back to the activity with the text changed to abc.
However, if I change the text to abc then click the nav bar to a new page and then click the nav bar back to the home page, the text has been reset to the original values and not abc.
I'm not really sure how else to explain the problem, anyone have any clues or want more clarification?
It is challenging to understand your app functionality without code base and UI. From my understanding, I believe you are not using the savedInstancestate bundle object to save your data whenever you are clicking the back button on the nav bar. You must bundle your data before going back to your activity or launching a new activity/fragment if you want to save your text changes. Look into two things:
Activity/Fragment lifecycle.
SavedInstanceState
Your fragment need tag or id when adding/replace in order to restore.
String mCurrentOverlayFragmentTag = "ControlOverlayFragment";
getFragmentManager()
.beginTransaction()
.replace(R.id.overlayHolder, fragment, mCurrentOverlayFragmentTag)
.commit();
Related
I have two fragments (for ex. fragmentA and fragmentB).
first , in fragmentA use findNavController().navigate(R.id.action_fragmentA_to_fragmentB) to navigate to fragmentB .
then , in fragmentB if you want to back to fragmentA. there are two ways in below :
just press back button : fragmentA's onCreate() won't be called
findNavController().navigate(R.id.action_fragmentB_to_fragmentA) : fragmentA's onCreate() will be called
why?
The reason that the back button doesn't call onCreate of the fragment is by design. Users would not expect the back button to call the onCreate, or create, your fragment again.
As an example, think about when you open the YouTube app on Android and you are shown your home screen, populated with videos based on your interests. When you tap on a video after a bit of scrolling and then midway through the video decide to go back by pressing the back button, you expect the app to go back where you tapped on the video, with the same amount of scrolling you had done, instead of reloading your entire home page again filling with new videos and resetting you to the top of the screen.
Similarly, back button in your app should do the same. If however, you want your back button to behave differently, android does provide a way to do this. Refer to this for that.
I have a BottomNavigation implemented in my app. when i tap on navigation items it shows their respective fragments, it is working fine. I have implemented a progress bar in every fragment so whenever i select a fragment from BottomNavigation the progress bar displays, my question is when i select any option from BottomNavigation progress bar shows then fragments load but when the fragment is loaded it should gets saved when i come back to that option from BottomNavigation it loads again... is there any way to save the state of that fragment so that it only loads for the first time.
Use onSavedInstanceState(Bundle) This will get you the required behavior, so this method is called before an activity may be killed so that when it comes back some time in the future it can restore its state.
Here i use activity which in respect is any activity, even if its a fragment, this example is from the official documentation.
For example, if activity B is launched in front of activity A, and at some point activity A is killed to reclaim resources, activity A will have a chance to save the current state of its user interface via this method so that when the user returns to activity A, the state of the user interface can be restored via onCreate(Bundle) or onRestoreInstanceState(Bundle).
check out this cool link, it describes everything and a little bit more: https://inthecheesefactory.com/blog/fragment-state-saving-best-practices/en
I'm trying out Android's new Navigation Editor for the first time and I'm not sure if this is a missing feature, intentional omission, or if I'm missing something. I have two fragments and I want the first fragment to be able to navigate to the second one, but I want the activity to finish if back is pressed from either fragment.
With my current setup, I can navigate from mainFragment to newFragment. If I press back from the mainFragment, the activity finishes. The only piece I can't figure out is how to finish the activity when back is pressed from newFragment. I've tried every combination of Pop Behavior settings, but haven't achieved what I'm looking for.
Just set clearTask to "true" on your action.
But your use case is going against the concept of the navigation.
https://developer.android.com/topic/libraries/architecture/navigation/navigation-principles#the_app_should_have_a_fixed_starting_destination
Apps have a fixed destination which is the screen the user sees when they launch your app from the launcher. This destination should also be the last screen the user sees when they return to the launcher after pressing the back button.
See the screenshot and look for Pop Behavior. This option can be used to finish activity.
Please note: Finish activity = pop the Activity off the stack.
Select the action from the Activity to be finished, in navigation graph.
Look for drop down for Pop To.
Select the fragment(i.e. the navHostFragment of the activity to be finished).
Check Inclusive option. (i.e. From current destination point- in ur case, it's an action - to and including this fragment - in ur case navHostFragment of Activity- in the stack will be popped off the stack. And that's what we need!).
On my app I am using a Main Activity, which has a Navigation Drawer, and as the user go to an options from the drawer, it will change the fragment beging displayed accordingly to the option selected.
If the user hit's "Back button" several times, it will go back to a point in which it will reach my Main Activity, which is a blank and empty layout.
When I reach this point (my main activit, empty), I would like to exit the app, or, open the Navigation Drawer.
The problem is, I don't know any event that shows me that I am back to the Main Activity. I checked the onResume, but it's never called, which makes sense, since the main activity has never been stopped.
I thought perhaps there would be an event from the fragment manager that would be called on the Main Activity when a fragment was detached, and from there I could check if there was no fragment at all attached?
When you push your first fragment, add a tag to it. Something like
transaction.replace( R.id.rootContainer, firstFragment, "rootFragment");
Whenever user presses back button, you can get your rootFragment from FragmentManager
FirstFragment myFragment = (FirstFragment) getSupportFragmentManager().findFragmentByTag("rootFragment");
And check if this fragment is visible or not, by myFragment.isVisible(), if not, then keep popping the stack, if it is visible, it means user is on the first fragment. Now you can either quit the app, or show your menu drawer.
Good night good sir. Thank you for your tip.
I used a different approach, based on your repply, that gave me quite a few insights.
On main activity, I Overrided the onKeyDown and check if it was pressed the Back Button. If yes, then I check the size of my Back Stack.
Uppon that, I decide if I want to finish my application.
Also, thanks for the tip of "labeling" the fragments on the back stack, didn't know I could do that.
I have 3 fragments : A, B and C.
A contents a list of element, when you chose an element from the list, it loads B fragment. Inside B, i have a button showPreview, a click on that button loads the C fragment.
I already implemented all of this, and it's working pretty nice.
Now what i want is to add, in A fragment, a shortcut button on each item, to access the preview (C fragment) without showing B fragment on UI like in google play application, you can download an app by clicking on Three dots -> Install, without opening app detail page.
Presently, when user clicks on shortcut button, i load the B fragment first (shown in UI), after i call previewButton.performClick() to click programmatically on the showPreview button. But that's not what i want because i am obliged to show B first, let it load entirely before making a performClick().
I have read about FragmentTransaction methods (attach/detach, add/remove etc.), about fragment lifecycle, etc ... without solution.
So my questions are :
how can i load B fragment without showing it on the UI ?
If that's impossible, how to do the same thing as google play application ?
Finally I resolved the issue. My problem was that I haven't seperate Views from Model. I didn't have to use performClick() anyway, I didn't have to depend on Button click.
I resolved it by just creating a method which does nicely what I want, after I use this method on button click and after shortcut list choice.