OnAttach() is called when a fragment is connected to an activity. You will likely need to change the path for FooFragment based on your project setup. Presenting navigational components such as the navigation drawer or the viewpager. Screen Orientation – Often within apps, the portrait version of an activity has a substantially different layout from the landscape version.

These transactions are then added to the backstack, where later, the operations can be reversed. In order to make custom backstack popping easier, we just need to identify and group some of the fragments so that they can be manipulated out of sequence. When back button is pressed, the current fragment will pop off the top of the stack. If there is only one activity or fragment in the stack and you hit back it will exit the app.

In this file, I have written the code for the click event of both the buttons. This file will inflatefragment_fragment_two.xmlto create the look and feel of the second fragment. When we click the second button from activity, second fragment will entirely replace the first fragment. In this example, we will create a fixed space into the area of activity. In this fixed space, we will show up two fragments one by one.

Simplifying the FragmentManager API: Multiple Fragment backstacks on Android

The second way is by adding the fragment dynamically in Java using the FragmentManager. The FragmentManager class and the FragmentTransaction class allow you to add, remove and replace fragments in the layout of your activity at runtime. The above is part of the base Fragment class we created for all our fragments. Because the fragment can be recreated when Activity configuration changes , we only create “fragmentTag” once and save it in the bundle.

fragment backstack

The back stack of fragments is simply a way of allowing the fragment system to help you handle BACK navigation. I am assuming this is because, as my log says fragment 1 already exists in the back stack App Development Costs , and i should rather use replace(..), but again, not gettinga fragment with saved data. Multiple stacks within multiple stacksWith the above, the FragmentManager’s robustness is clear to see.

The transaction also needs to be tagged correctly when it is added to the backstack to support using the tag with popBackStack. What you are doing is adding to the back stack regardless of whether or not the back stack was popped. The other option is to pass in zero, which will pop everything up to the specified state.

From what i have understood, replace is like calling transaction.remove for all the fragments (in fragManager’s backstack i guess?) and then calling fragManager.add . Note that the fragment’s method is called only when the Activity didn’t consume the event first. Be sure to check out a more detailed guide about fragments and action bar if you have more questions. A few exceptions to this are dialog fragments presented from within another fragment or nested child fragments. Both of these cases are situations where a fragment has nested child fragments and that are therefore allowed to communicate upward to their parent .

Since Android 4.2, you have the ability to embed a fragment within another fragment. A common situation where you might want to nest fragments is when you are using a sliding drawer for top-level navigation and one of the fragments needs to display tabs. Check out this stackoverflow for a discussion on deciding when to replace vs hide and show.

Inside of an app which uses fragments extensively, we need to keep in mind that the role of an activity shifts. Tablet Support – Often within apps, the tablet version of an activity has a substantially different layout from the phone version How to Make a Cryptocurrency which is different from the TV version. Fragments enable device-specific activities to reuse shared elements while also having differences. A Fragment is a combination of an XML layout file and a java class much like an Activity.

In this case, the backwards navigation isn’t what we expect. I was under the impression that navigation component always does a replace instead of an add. However you can replace or pop up to as well depending on your use case. Here it is false, so if a user clicks back button, the app will be closed because nothing was saved in the backstack. Android Studio will be used to make android fragments tutorial with example.

Get the Medium app

This post will give you an introduction to fragment backstack and how to put one fragment in a backstack and how to remove it from the backstack. FragmentOperator also supports popping all the way back to root child fragment, just like iOS. When you need to set a Fragment class to be single instance in backstack, just add annotationSingleInstanceFragment to your Fragment class. We’ve encapsulated all of the above fragment management code in an open-source library called FragmentOperator.

fragment backstack

I find the How to Start Freelancing as a Web Developer in 2022 can be tricky to get right and get my head around. When I was googling this stuff years ago I was surprised at the lack of blogposts and discussion on how difficult it is. We will see how to handle and manage backstack of fragments. We will change the value of the textview on the click event of both the buttons.

When the MultiStackNavigator is resumed after process death however, all its StackFragments are already preserved in the FragmentManager, so it only needs to retrieve them. Fragment transactions can involve two different types of tags. The one that most Android developers are familiar with is the Fragment tag, which you can use to find a specific Fragment in your FragmentManager later via findFragmentByTag(). This is useful for finding a Fragment when your application is in a particular state, but keep in mind that the Fragment needs to be added to your FragmentManager. If you have removed() or replaced() a Fragment and haven’t added it to the backstack, you won’t be able to find it. Fragments should generally only communicate with their direct parent activity.

Similar to above example, framelayout will hold the fragment. Select empty activity as a default activity to have pure clean project. This example is about the demonstration about controlling the UI widgets of the fragments. First one is the name of the fragment which we want to open in the framelayout.


In my example this would leave the current tab on the backstack, so hitting back after navigating to a tab would bring you back to the previous tab. When you are working with fragment as with activities, you need to make sure to handle configuration changes such as screen rotation or the activity being closed. Be sure to review the configuration changes guide for more details on how to save and restore fragment state. The important thing to keep in mind is that fragments should not directly communicate with each other and should generally only communicate with their parent activity.

In this article, I will cover about the fragment implementation and it’s usage. If 0 it will not remove the transaction whose name is given. It will be removed only if we provide any other value like 1. You need build a Fragment to host all tabs and implement TabsNavigator.

  • Every fragment is attached to the activity, and is saved to the back stack without any problem.
  • When you are working with fragment as with activities, you need to make sure to handle configuration changes such as screen rotation or the activity being closed.
  • FragmentOperator also supports another level of backstack navigation along with Activity backstack.

Every fragment is attached to the activity, and is saved to the back stack without any problem. I’m actually just going to be using one tag, which identifies the current “first level” Fragment on the stack. Check the guides linked above for detailed steps for each of these approaches. // onViewCreated() is only called if the view returned from onCreateView() is non-null.

Not the answer you’re looking for? Browse other questions tagged androidandroid-fragmentsback-stack or ask your own question.

Here, we have created both the fragment such that we can use them with single activity as well as with separate activities. Hence, fragments have demonstrated the re usability feature. When you divide the activity’s layout into various components using fragments, you are able to change the activity’s look and feel at the runtime. To build a multi pane User Interface, you can combine multiple fragments in a single activity. If we add any fragment transaction to a backstack, the listener will show all entries.

OnViewCreated() is called after onCreateView() and ensures that the fragment’s root view is non-null. Fragments are standalone components that can contain views, events and logic. Now we have two HomeFragment instances and this is the reason why we need to hit the back button twice to exit the app.