ClassNotFoundException when using androidx.fragment.app.FragmentContainerView

Question

I'm trying to transition from using a FrameLayout to using FragmentContainerView and from the tutorials I've seen, it should be pretty easy. However, when I run my app after making the change, I get

Error inflating class androidx.fragment.app.FragmentContainerView
Caused by: java.lang.ClassNotFoundException: androidx.fragment.app.FragmentContainerView

my layout file is pretty simple:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="match_parent"
android:layout_width="match_parent"
xmlns:tools="http://schemas.android.com/tools"
tools:showIn="@layout/app_bar_main">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragment_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

Do I need to add something into my build.gradle or something? Why can't it find the class?

If it is happening only in release builds, then it is a pro-guard issue. Check this quick fix: https://stackoverflow.com/a/61365688/3484700 — Salam El-Banna, Jul 12 '20 at 15:17

score 35 · Accepted Answer · answered Jan 31 '20 at 19:11

35

That's in androidx.fragment 1.2.0 or higher:

implementation "androidx.fragment:fragment:1.2.0"

answered Jan 31 '20 at 19:11

CommonsWare

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1

Thanks! I figured I needed a statement like that, just couldn't find any documentation on how to format it – Randy Feb 01 '20 at 02:29
1

Same. It's a shame I had to google to find this. – wsgeorge Mar 12 '21 at 12:43
1

For kotlin implementation 'androidx.fragment:fragment-ktx:1.4.0' – void pointer Nov 23 '21 at 12:21

CoolMind · Answer 2 · 2020-12-24T07:45:56.037

Thanks to @Salam El-Banna and his link, I found that in case an application crashes in release build we should add in proguard-rules.pro (one or two lines, depending on android:name in <FragmentContainerView>:

#-------------------------------------------------
# JetPack Navigation
# This fixes: 
# Caused by: androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment androidx.navigation.fragment.NavHostFragment: make sure class name exists
# Caused by: androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment com.google.android.gms.maps.SupportMapFragment: make sure class name exists
#-------------------------------------------------

-keepnames class androidx.navigation.fragment.NavHostFragment
-keepnames class com.google.android.gms.maps.SupportMapFragment

score 0 · Answer 3 · answered Aug 26 '21 at 15:10

Make sure their are no custom constructors like this.
ex:

FragmentName (val ctx: Context): Fragment() {

change to

FragmentName: Fragment() {

The reason is when the inflater inflates FrgmentContainer, it calls default constructor to initialize the fragments. If their is no default constructor available, it will crash.

score 0 · Answer 4 · answered Sep 03 '21 at 13:43

0

If you are using kotlin the latest FragmentContainerView implementation stays under:

implementation("androidx.fragment:fragment-ktx:1.3.6")

answered Sep 03 '21 at 13:43

Nicola Gallazzi

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ClassNotFoundException when using androidx.fragment.app.FragmentContainerView

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