I've 2 fragments, A & B
with action:
<action
android:id="#+id/action_a_to_b"
app:destination="#id/b"
app:enterAnim="#android:anim/fade_in"
app:exitAnim="#android:anim/fade_out"
app:popEnterAnim="#android:anim/fade_in"
app:popExitAnim="#android:anim/fade_out"
app:popUpTo="#id/a"/>
after I move from a to b and pressing back,
and then try again to open b from a, the app crashes and the problem is that the navigation graph current destination remains fragment b instead of changing to a.
Update:
if fragment B inherit from Fragment class, it doesn't happen
if fragment B inherit from BottomSheetDialogFragment it does happen
any idea why?
Thanks.
The problem was that i used the tag instead of in the navigation graph...
Here is my code
<fragment
android:id="#+id/fragment1"
android:name="com.example.app.Fragment1"
android:label="SignatureFragment"
tools:layout="#layout/layout_fragment1">
<action
android:id="#+id/action_fragment1_to_main_activity"
app:destination="#id/main_activity"
app:enterAnim="#anim/slide_in_from_right"
app:exitAnim="#anim/no_anim"
app:launchSingleTop="true"
app:popEnterAnim="#anim/no_anim"
app:popExitAnim="#anim/slide_out_to_right"
app:popUpTo="#id/navigation_graph_id"
app:popUpToInclusive="true" />
</fragment>
<activity
android:id="#+id/main_activity"
android:name="com.example.app.MainActivity"
android:label="MainActivity"
tools:layout="#layout/activity_main" />
Now the code for navigation
findNavController().navigate(R.id.action_fragment1_to_main_activity)
When I navigate to activity and press back, the fragment is still there. I want to clear the backstack after opening the activity.
I tried to remove the animation and also tried with removing app:launchSingleTop, but no success.
Edit
Jetpack Navigation is intended to work with single activity and does not fully support activity navigation with parameters passed to actions
Thus to clear stack when navigating from one activity to another you will still need to call activity.finish()
Edit end
The thing is findNavController().navigate(R.id.action_fragment1_to_main_activity) wont work.
Try to navigate via navigate(#NonNull NavDirections directions). In your case it will look something like this
findNavController().navigate(
Fragment1Directions.actionFragment1ToMainActivity())
Hope it helps.
My flow of fragment is like this
Main -> A -> B -> C ->A
In fragment c, it has a submit button which will return to A.
When I press back button in A, I want it back to Main. But it return to fragment c instead.
In fragment C, I use this
findNavController().navigate(R.id.action_c_to_a)
nav_graph.xml
<fragment
android:id="#+id/fragmentC"
android:name="xxx"
android:label="xxx">
<action
app:launchSingleTop="true"
app:popUpTo="#+id/fragmentA"
app:popUpToInclusive="true"
android:id="#+id/action_c_to_a"
app:destination="#id/fragmentA" />
</fragment>
Why not pop up to fragment A? You could just call findNavController().popBackStack(R.id.fragmentA, false) instead of navigating with an action.
try to look at my complete solution with removing/killing fragment from backstack.
Navigation Component set transition animation programmatically
You can override the back button behavior to do this.
Provide custom back navigation
The idea is to set a app:popUpTo without setting app:destination. Indeed, setting a app:destination will create a fragment and add it to the backstack which is not what you want.
To you can just remove :
app:destination="#id/fragmentA"
If you have this :
app:popUpTo="#+id/fragmentA"
And it will really pop the backstack until fragmentA
I'm new to the Android Jetpack Navigation architecture. I'm trying it out on a new app. There's one activity and a few fragments, two of them are login screen and email login screen. I defined those fragments in my navigations XML. The flow of the app is as follows:
Login screen → Email Login screen
What I want is, after navigating to the email login screen, when I press back, the app exits. Meaning the back-stack for login screen is removed. I know login screens aren't supposed to work that way, but I'm still just figuring things out.
I followed the documentation from Google's Get started with the Navigation component. It said, using app:popUpTo and app:popUpToInclusive="true" is supposed to clear the backstack, yet when I press back on email login screen, it still goes back to login instead of exiting.
So, here's what I've tried.
nav_main.xml
<fragment android:id="#+id/loginFragment"
android:name="com.example.myapp.ui.main.LoginFragment"
android:label="#string/login"
tools:layout="#layout/fragment_login" >
<action
android:id="#+id/action_login_to_emailLoginFragment"
app:destination="#id/emailLoginFragment"
app:popEnterAnim="#anim/slide_in_right"
app:popExitAnim="#anim/slide_out_right"
app:popUpTo="#+id/emailLoginFragment"
app:popUpToInclusive="true"/>
</fragment>
<fragment android:id="#+id/emailLoginFragment"
android:name="com.example.myapp.ui.main.EmailLoginFragment"
android:label="EmailLoginFragment"
tools:layout="#layout/fragment_login_email" />
LoginFragment.kt
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
binding.emailLoginButton.setOnClickListener {
findNavController().navigate(R.id.action_login_to_emailLoginFragment)
}
return binding.root
}
I gave a click event to a button. In it, I used the Navigation Controller to navigate to the email login screen by giving it the action's ID. In the <action>, there are app:popUpTo and app:popUpToInclusive="true".
After reading the documentation over and over, as well as reading plenty of StackOverflow questions, I found those properties are supposed to remove my login screen off the back-stack. But they don't. The button does navigate to the email login screen, but when I press back, it still goes back to login screen instead of exiting the app. What am I missing?
<action
android:id="#+id/action_login_to_emailLoginFragment"
app:destination="#id/emailLoginFragment"
app:popEnterAnim="#anim/slide_in_right"
app:popExitAnim="#anim/slide_out_right"
app:popUpTo="#+id/loginFragment"
app:popUpToInclusive="true"/>
Your popUpTo is going back to the email login, and then popping it because of the inclusive.
If you will change the popUpTo to your login fragment, it will be navigated back to, and popped as well because of the inclusive flag, which will result in your desired behaviour.
I write this answer for people who have not completely understood the
way popUpTo works and I hope its example helps someone because most
examples for navigation are repetitive in most sites and do not show
the whole picture.
In any <action> if we write a value for app:popUpTo, it means we want to delete some of the fragments from the back stack just after completing the action, but which fragments are going to be removed from the back stack when action is completed?
Its order is Last In First Out so:
All fragments between the last fragment and the fragment defined in popUpTo will be removed.
And if we add app:popUpToInclusive="true", then the fragment defined
in popUpTo will also be removed.
Example:
Consider fragments from A to G in a navigation graph like this:
A->B->C->D->E->F->G
We can go from A to B and then from B to C and so on. Consider the following two actions:
An action E->F we write:
<action
...
app:destination="#+id/F"
app:popUpTo="#+id/C"
app:popUpToInclusive="false"/>
And for F->G we write:
<action
...
app:destination="#+id/G"
app:popUpTo="#+id/B"
app:popUpToInclusive="true"/>
Then after going from E to F using the action E->F, the fragments between the last fragment (F) and C (which is defined in popUpTo of E->F) will be removed. The fragment C will not be removed this time because of app:popUpToInclusive="false" so our back stack becomes:
A->B->C->F (F is currently on Top)
Now if we go to fragment G using action F->G :
all fragments between the last fragment(G) and B (which is defined in popUpTo of F->G ) will be removed but this time the fragment B will also be removed because in F->G action we wrote app:popUpToInclusive="true" . so back stack becomes:
A->G (G is on top now)
These 2 lines make the trick works:
If you want to go from A to B and expect to finish A:
You need to call B with this action:
<fragment
android:id="#+id/fragmentA"
tools:layout="#layout/fragment_a">
<action
android:id="#+id/action_call_B"
app:destination="#+id/fragmentB"
app:popUpTo="#id/fragmentA"
app:popUpToInclusive="true" />
</fragment>
<fragment
android:id="#+id/fragmentB"
tools:layout="#layout/fragment_b">
</fragment>
If you put log to your fragments you can see that fragmentA is destroyed after calling fragmentB with this action.
You can do it in XML just like this answer does, or you can also do it programmatically:
NavOptions navOptions = new NavOptions.Builder().setPopUpTo(R.id.loginRegister, true).build();
Navigation.findNavController(mBinding.titleLogin).navigate(R.id.login_to_main, null, navOptions);
Let's say that your app has three destinations—A, B, and C—along with actions that lead from A to B, B to C, and C back to A. The corresponding navigation graph is shown in figure
With each navigation action, a destination is added to the back stack. If you were to navigate repeatedly through this flow, your back stack would then contain multiple sets of each destination (A, B, C, A, B, C, A, and so on). To avoid this repetition, you can specify app:popUpTo and app:popUpToInclusive in the action that takes you from destination C to destination A, as shown in the following example:
<fragment
android:id="#+id/c"
android:name="com.example.myapplication.C"
android:label="fragment_c"
tools:layout="#layout/fragment_c">
<action
android:id="#+id/action_c_to_a"
app:destination="#id/a"
app:popUpTo="#+id/a"
app:popUpToInclusive="true"/>
After reaching destination C, the back stack contains one instance of each destination (A, B, C). When navigating back to destination A, we also popUpTo A, which means that we remove B and C from the stack while navigating. With app:popUpToInclusive="true", we also pop that first A off of the stack, effectively clearing it. Notice here that if you don't use app:popUpToInclusive, your back stack would contain two instances of destination A
popUpTo its to define the place that you want to go when you press back. If you set popUpInclusive = true, the navigation skipe that place too ( in popUpTo ).
Sample: A -> B -> A
FragmentB.kt
Attempts to pop the controller's back stack
private fun popBackStackToA() {
if (!findNavController().popBackStack()) {
// Call finish on your Activity
requireActivity().finish()
}
}
Back Stack
I faced a similar problem and my approach was simple. In the navigation graph, you have to designate the starting screen. Mine was:
app:startDestination="#id/webview"
It's called the start destination, it is the first screen users see when opening your app, and it's the last screen users see when exiting your app.
If you do not wish your login activity to be shown as you exit the app, just remove it as the start destination and use the fragment that you wish to show last in your case, It's the Email Login screen.
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/nav"
app:startDestination="#id/Email Login screen">
Also, make sure you override the onBackPressed() method from the host activity code as:
override fun onBackPressed() {
finish()
super.onBackPressed()
}
Now that you have removed the login fragment as the start destination, it's now not obvious what fragment will be shown first when the app opens.
Add a method to implement that in the host activity and call it from the oncreate(). In my case,i created initContent() to handle that logic. This was the code:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val navHostFragment = supportFragmentManager
.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
navController = navHostFragment.navController
if (savedInstanceState == null) {
initContent()
}
}
private fun initContent() {
if (isNetworkConnected()) {
navController.navigate(R.id.webView)
} else {
navController.navigate(R.id.noInternetFragment)
}
}
Hope this helps someone.
I am using the new AndroidX navigation framework.
I have a few fragments all linked in a navigation chain.
FragmentA --> FragmentB --> FragmentC
FragmentC has a Cancel button that should send me up all the way back to FragmentA.
Should I do the following:
on FragmentC call the method:
Navigation.findNavController(view).navigateUp();
then on FragmentB listen to some callback and using some passed parameter or argument trigger another navigateUp() function from FragmentB
or is there some method that will do the equivalent of navigateUpTwice()
What I ended up doing was
Navigation.findNavController(view).popBackStack(R.id.fragmant_a,false)
In your navigation.xml file under the action that you have created to navigate to starting fragment (FragmentA in your case) add the following
<action
....
app:popUpTo="#id/fragmentA"
app:popUpToInclusive="false"/>
This will pop up all the fragments until FragmentA and will exclude FragmentA since popUpToInclusive is set to false.
Edit:
The full form of your action under FragmentC tag of your navigation.xml file will be something similar to this:
<fragment
android:id="#+id/FragmentC"
android:name="com.yourdomain.FragmentC"
android:label="FragmentC">
<action
android:id="#+id/action_fragmentC_to_fragmentA"
app:destination="#id/fragmentA"
app:popUpTo="#id/fragmentA"
app:popUpToInclusive="false"/>
</fragment>
Try with this, it works for me.
findNavController().navigateUp()
findNavController().navigateUp()
You can set pop To FragmentA in your action from FragmentB --> FragmentC and when then you press back it goes to Fragment A instead of Fragment B
So I found myself in a situation where I had to navigateUp() twice, but with a twist: I could reach the view through several paths. Think of it like this:
Fragment A --> Fragment C --> Fragment D
Fragment B --> Fragment C --> Fragment D
In a normal situation, using the popTo xml attribute or the popBackStack() method would work. However it is unusable here. Fortunately, what you can do is:
val navController = NavHostFragment.findNavController(this)
navController.navigateUp()
navController.navigateUp
As other people have pointed out, this is absolutely not optimised performance-wise. In any situation where you can reach Fragment D through a single path, use popTo instead.