This guide covers tools that you can use to debug your fragments.
FragmentManager logging
FragmentManager
is capable of emitting various messages to
Logcat. This is disabled by default to avoid adding
noise to Logcat, but sometimes these log messages can help you troubleshoot
issues with your fragments. FragmentManager
emits the most meaningful output
at the Debug and Verbose log levels.
You can enable logging using the
adb shell
command:
adb shell setprop log.tag.FragmentManager DEBUG
Alternatively, you can enable verbose logging:
adb shell setprop log.tag.FragmentManager VERBOSE
If you enable verbose logging, you can then apply a log level
filter in the Logcat window. However, this
will filter all logs, not just the FragmentManager
logs. It's usually best to
enable FragmentManager
logging only at the log level that you need.
DEBUG logging
At DEBUG
level FragmentManager
generally emits log messages relating to
lifecycle state changes. Each log entry contains the toString()
dump from the Fragment
.
A log entry consists of the following information:
- The simple class name of the
Fragment
instance. - The identity hash code
of the
Fragment
instance. - The
FragmentManager
’s unique ID of theFragment
instance. This is stable across configuration changes and process death and recreation. - The ID of the container that the
Fragment
was added to, but only if set. - The
Fragment
tag, but only if set.
D/FragmentManager: moveto ATTACHED: NavHostFragment{92d8f1d} (fd92599e-c349-4660-b2d6-0ece9ec72f7b id=0x7f080116)
You can identity the Fragment from the following:
- The
Fragment
class isNavHostFragment.
- The identity hash code is
92d8f1d
. - The unique ID is
fd92599e-c349-4660-b2d6-0ece9ec72f7b
. - The container ID is
0x7f080116
. - The tag is omitted because none was set. If it were present, it would follow
the ID in the format
tag=tag_value
.
For brevity and readability, the UUIDs have been shortened in the following examples.
Here we see a NavHostFragment
initialized and then the startDestination
Fragment
of type FirstFragment
being created and transitioning through to
RESUMED
state:
D/FragmentManager: moveto ATTACHED: NavHostFragment{92d8f1d} (<UUID> id=0x7f080116) D/FragmentManager: mName=null mIndex=-1 mCommitted=false D/FragmentManager: Operations: D/FragmentManager: Op #0: SET_PRIMARY_NAV NavHostFragment{92d8f1d} (<UUID> id=0x7f080116) D/FragmentManager: moveto CREATED: NavHostFragment{92d8f1d} (<UUID> id=0x7f080116) D/FragmentManager: mName=null mIndex=-1 mCommitted=false D/FragmentManager: Operations: D/FragmentManager: Op #0: REPLACE FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: Op #1: SET_PRIMARY_NAV FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto ATTACHED: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto CREATED: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto CREATE_VIEW: NavHostFragment{92d8f1d} (<UUID> id=0x7f080116) D/FragmentManager: moveto CREATE_VIEW: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto ACTIVITY_CREATED: NavHostFragment{92d8f1d} (<UUID> id=0x7f080116) D/FragmentManager: moveto RESTORE_VIEW_STATE: NavHostFragment{92d8f1d} (<UUID> id=0x7f080116) D/FragmentManager: moveto ACTIVITY_CREATED: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto RESTORE_VIEW_STATE: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto STARTED: NavHostFragment{92d8f1d} (<UUID> id=0x7f080116) D/FragmentManager: moveto STARTED: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto RESUMED: NavHostFragment{92d8f1d} (<UUID> id=0x7f080116) D/FragmentManager: moveto RESUMED: FirstFragment{ccd2189} (<UUID> id=0x7f080116)
Following a user interaction, we see FirstFragment
transition out of the
various lifecycle states. Then SecondFragment
is instantiated and transitions
through to RESUMED
state:
D/FragmentManager: mName=07c8a5e8-54a3-4e21-b2cc-c8efc37c4cf5 mIndex=-1 mCommitted=false D/FragmentManager: Operations: D/FragmentManager: Op #0: REPLACE SecondFragment{84132db} (<UUID> id=0x7f080116) D/FragmentManager: Op #1: SET_PRIMARY_NAV SecondFragment{84132db} (<UUID> id=0x7f080116) D/FragmentManager: movefrom RESUMED: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: movefrom STARTED: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: movefrom ACTIVITY_CREATED: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto ATTACHED: SecondFragment{84132db} (<UUID> id=0x7f080116) D/FragmentManager: moveto CREATED: SecondFragment{84132db} (<UUID> id=0x7f080116) D/FragmentManager: moveto CREATE_VIEW: SecondFragment{84132db} (<UUID> id=0x7f080116) D/FragmentManager: moveto ACTIVITY_CREATED: SecondFragment{84132db} (<UUID> id=0x7f080116) D/FragmentManager: moveto RESTORE_VIEW_STATE: SecondFragment{84132db} (<UUID> id=0x7f080116) D/FragmentManager: moveto STARTED: SecondFragment{84132db} (<UUID> id=0x7f080116) D/FragmentManager: movefrom CREATE_VIEW: FirstFragment{ccd2189} (<UUID> id=0x7f080116) D/FragmentManager: moveto RESUMED: SecondFragment{84132db} (<UUID> id=0x7f080116)
All the Fragment instances are suffixed by an identifier so that you can track
different instances of the
same Fragment
class.
VERBOSE logging
At VERBOSE
level, FragmentManager
generally emits log messages about its
internal state:
V/FragmentManager: Run: BackStackEntry{f9d3ff3} V/FragmentManager: add: NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: Added fragment to active set NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) D/FragmentManager: moveto ATTACHED: NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: Commit: BackStackEntry{5cfd2ae} D/FragmentManager: mName=null mIndex=-1 mCommitted=false D/FragmentManager: Operations: D/FragmentManager: Op #0: SET_PRIMARY_NAV NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) D/FragmentManager: moveto CREATED: NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: Commit: BackStackEntry{e93833f} D/FragmentManager: mName=null mIndex=-1 mCommitted=false D/FragmentManager: Operations: D/FragmentManager: Op #0: REPLACE FirstFragment{886440c} (<UUID> id=0x7f080130) D/FragmentManager: Op #1: SET_PRIMARY_NAV FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: Run: BackStackEntry{e93833f} V/FragmentManager: add: FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: Added fragment to active set FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for FirstFragment{886440c} (<UUID> id=0x7f080130) D/FragmentManager: moveto ATTACHED: FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for FirstFragment{886440c} (<UUID> id=0x7f080130) D/FragmentManager: moveto CREATED: FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 1 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) D/FragmentManager: moveto CREATE_VIEW: NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 2 for FirstFragment{886440c} (<UUID> id=0x7f080130) D/FragmentManager: moveto CREATE_VIEW: FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 2 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 2 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) D/FragmentManager: moveto ACTIVITY_CREATED: NavHostFragment{86274b0} (<UUID> id=0x7f080130) D/FragmentManager: moveto RESTORE_VIEW_STATE: NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for FirstFragment{886440c} (<UUID> id=0x7f080130) D/FragmentManager: moveto ACTIVITY_CREATED: FirstFragment{886440c} (<UUID> id=0x7f080130) D/FragmentManager: moveto RESTORE_VIEW_STATE: FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: SpecialEffectsController: Enqueuing add operation for fragment FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: SpecialEffectsController: For fragment FirstFragment{886440c} (<UUID> id=0x7f080130) mFinalState = VISIBLE -> VISIBLE. V/FragmentManager: SpecialEffectsController: Container androidx.fragment.app.FragmentContainerView{7578ffa V.E...... ......I. 0,0-0,0 #7f080130 app:id/nav_host_fragment_content_fragment} is not attached to window. Cancelling pending operation Operation {382a9ab} {mFinalState = VISIBLE} {mLifecycleImpact = ADDING} {mFragment = FirstFragment{886440c} (<UUID> id=0x7f080130)} V/FragmentManager: SpecialEffectsController: Operation {382a9ab} {mFinalState = VISIBLE} {mLifecycleImpact = ADDING} {mFragment = FirstFragment{886440c} (<UUID> id=0x7f080130)} has called complete. V/FragmentManager: SpecialEffectsController: Setting view androidx.constraintlayout.widget.ConstraintLayout{3968808 I.E...... ......I. 0,0-0,0} to VISIBLE V/FragmentManager: computeExpectedState() of 4 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: SpecialEffectsController: Enqueuing add operation for fragment NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: SpecialEffectsController: For fragment NavHostFragment{86274b0} (<UUID> id=0x7f080130) mFinalState = VISIBLE -> VISIBLE. V/FragmentManager: SpecialEffectsController: Container androidx.fragment.app.FragmentContainerView{2ba8ba1 V.E...... ......I. 0,0-0,0 #7f080130 app:id/nav_host_fragment_content_fragment} is not attached to window. Cancelling pending operation Operation {f7eb1c6} {mFinalState = VISIBLE} {mLifecycleImpact = ADDING} {mFragment = NavHostFragment{86274b0} (<UUID> id=0x7f080130)} V/FragmentManager: SpecialEffectsController: Operation {f7eb1c6} {mFinalState = VISIBLE} {mLifecycleImpact = ADDING} {mFragment = NavHostFragment{86274b0} (<UUID> id=0x7f080130)} has called complete. V/FragmentManager: SpecialEffectsController: Setting view androidx.fragment.app.FragmentContainerView{7578ffa I.E...... ......I. 0,0-0,0 #7f080130 app:id/nav_host_fragment_content_fragment} to VISIBLE V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: Run: BackStackEntry{5cfd2ae} V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 4 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 5 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) D/FragmentManager: moveto STARTED: NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 5 for FirstFragment{886440c} (<UUID> id=0x7f080130) D/FragmentManager: moveto STARTED: FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 5 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 5 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 5 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 5 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 7 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 7 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) D/FragmentManager: moveto RESUMED: NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 7 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 7 for FirstFragment{886440c} (<UUID> id=0x7f080130) D/FragmentManager: moveto RESUMED: FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 7 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 7 for FirstFragment{886440c} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 7 for NavHostFragment{86274b0} (<UUID> id=0x7f080130) V/FragmentManager: computeExpectedState() of 7 for NavHostFragment{86274b0} (<UUID> id=0x7f080130)
This only covers the loading on FirstFragment
. Including the transition to
SecondFragment
would have increased the log entries considerably.
Much of the VERBOSE
level log messages will be of little to no use to app
developers. However, seeing when changes to the back stack occur may help in
debugging some issues.
StrictMode for fragments
Version 1.4.0 and higher of the Jetpack Fragment library includes StrictMode for fragments. It can catch some common issues which may cause your app to behave in unexpected ways.
By default, Fragment StrictMode has a
LAX
policy that catches nothing. However, it is possible to create custom policies.
A custom
Policy
defines which violations are detected and specifies what penalty is applied
when violations are detected.
To apply a custom StrictMode policy, assign it to the
FragmentManager
.
You should do this as early as possible. In this case, you do it in an
init
block or in the Java constructor:
Kotlin
class ExampleActivity : AppCompatActivity() { init { supportFragmentManager.strictModePolicy = FragmentStrictMode.Policy.Builder() .penaltyDeath() .detectFragmentReuse() .allowViolation(FirstFragment::class.java, FragmentReuseViolation::class.java) .build() } override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) val binding = ActivityExampleBinding.inflate(layoutInflater) setContentView(binding.root) ... } }
Java
class ExampleActivity extends AppCompatActivity() { ExampleActivity() { getSupportFragmentManager().setStrictModePolicy( new FragmentStrictMode.Policy.Builder() .penaltyDeath() .detectFragmentReuse() .allowViolation(FirstFragment.class, FragmentReuseViolation.class) .build() ); } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState) ActivityExampleBinding binding = ActivityExampleBinding.inflate(getLayoutInflater()); setContentView(binding.getRoot()); ... } }
For cases where you need to know the Context
to determine whether or not to
enable strict mode (for example, from the value of a boolean resource), you can
defer assigning a StrictMode policy to the FragmentManager
using an
OnContextAvailableListener
:
Kotlin
class ExampleActivity : AppCompatActivity() { init { addOnContextAvailableListener { context -> if(context.resources.getBoolean(R.bool.enable_strict_mode)) { supportFragmentManager.strictModePolicy = FragmentStrictMode.Policy.Builder() .penaltyDeath() .detectFragmentReuse() .allowViolation(FirstFragment::class.java, FragmentReuseViolation::class.java) .build() } } } override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) val binding = ActivityExampleBinding.inflate(layoutInflater) setContentView(binding.root) ... } }
Java
class ExampleActivity extends AppCompatActivity() { ExampleActivity() { addOnContextAvailableListener((context) -> { if(context.getResources().getBoolean(R.bool.enable_strict_mode)) { getSupportFragmentManager().setStrictModePolicy( new FragmentStrictMode.Policy.Builder() .penaltyDeath() .detectFragmentReuse() .allowViolation(FirstFragment.class, FragmentReuseViolation.class) .build() ); } } } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState) ActivityExampleBinding binding = ActivityExampleBinding.inflate(getLayoutInflater()); setContentView(binding.getRoot()); ... } }
The latest point at which you should configure strict mode to catch all possible
violations is in
onCreate()
,
but here you must configure strict mode before the call to super.onCreate()
:
Kotlin
class ExampleActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { supportFragmentManager.strictModePolicy = FragmentStrictMode.Policy.Builder() .penaltyDeath() .detectFragmentReuse() .allowViolation(FirstFragment::class.java, FragmentReuseViolation::class.java) .build() super.onCreate(savedInstanceState) val binding = ActivityExampleBinding.inflate(layoutInflater) setContentView(binding.root) ... } }
Java
class ExampleActivity extends AppCompatActivity() { @Override protected void onCreate(Bundle savedInstanceState) { getSupportFragmentManager().setStrictModePolicy( new FragmentStrictMode.Policy.Builder() .penaltyDeath() .detectFragmentReuse() .allowViolation(FirstFragment.class, FragmentReuseViolation.class) .build() ); super.onCreate(savedInstanceState) ActivityExampleBinding binding = ActivityExampleBinding.inflate(getLayoutInflater()); setContentView(binding.getRoot()); ... } }
This policy used in these examples detects only fragment reuse violations,
and the app terminates whenever one occurs. penaltyDeath()
can be
helpful in debug builds because it fails quickly enough that you cannot ignore
violations.
It is also possible to selectively allow certain violations. In the example, However, this policy enforces this violation for all other fragment types. This is useful for cases where a third-party library component might contain StrictMode violations. In such cases, you can temporarily add those violations to the allow list of your StrictMode for components that you don’t own until the library fixes their violation.
See the documentation for
FragmentStrictMode.Policy.Builder
for details on how to configure other violations.
There are three penalty types.
penaltyLog()
dumps details of violations toLogCat
penaltyDeath()
terminates the app when violations are detected.penaltyListener()
allows you to add a custom listener, which gets called whenever violations are detected.
You can apply any combination of penalties in your Policy
. If your policy does
not explicitly specify a penalty, a default of penaltyLog()
is applied. If you
apply a penalty other than penaltyLog()
in your custom Policy
, then
penaltyLog()
will be disabled unless you explicitly set it.
penaltyListener()
can be useful when you have a third-party logging library to
which you want to log violations. Alternatively, you might want to enable
non-fatal violation catching in release builds and log them to a crash reporting
library. This strategy can detect violations in the wild.
Setting a global StrictMode policy is best done by setting a default policy that
applies to all
FragmentManager
instances via the
FragmentStrictMode.setDefaultPolicy()
method:
Kotlin
class MyApplication : Application() { override fun onCreate() { super.onCreate() FragmentStrictMode.defaultPolicy = FragmentStrictMode.Policy.Builder() .detectFragmentReuse() .detectFragmentTagUsage() .detectRetainInstanceUsage() .detectSetUserVisibleHint() .detectTargetFragmentUsage() .detectWrongFragmentContainer() .apply { if (BuildConfig.DEBUG) { // Fail early on DEBUG builds penaltyDeath() } else { // Log to Crashlytics on RELEASE builds penaltyListener { FirebaseCrashlytics.getInstance().recordException(it) } } } .build() } }
Java
public class MyApplication extends Application { @Override public void onCreate() { super.onCreate(); FragmentStrictMode.Policy.Builder builder = new FragmentStrictMode.Policy.Builder(); builder.detectFragmentReuse() .detectFragmentTagUsage() .detectRetainInstanceUsage() .detectSetUserVisibleHint() .detectTargetFragmentUsage() .detectWrongFragmentContainer(); if (BuildConfig.DEBUG) { // Fail early on DEBUG builds builder.penaltyDeath(); } else { // Log to Crashlytics on RELEASE builds builder.penaltyListener((exception) -> FirebaseCrashlytics.getInstance().recordException(exception) ); } FragmentStrictMode.setDefaultPolicy(builder.build()); } }
The following sections describe types of violations and possible workarounds.
Fragment reuse
The fragment reuse violation is enabled using
detectFragmentReuse()
and throws a
FragmentReuseViolation
.
This violation indicates the reuse of a Fragment
instance after its removal
from FragmentManager
. This reuse can cause issues because the Fragment
may
retain state from its previous use and not behave consistently. If you create a
new instance each time, it will always be in the initial state when added to
FragmentManager
.
Fragment tag usage
The fragment tag usage violation is enabled using
detectFragmentTagUsage()
and throws a
FragmentTagUsageViolation
.
This violation indicates that a Fragment
was inflated using the <fragment>
tag in an XML layout. To resolve this, inflate your Fragment
inside
<androidx.fragment.app.FragmentContainerView>
rather than in the <fragment>
tag. Fragments inflated using a FragmentContainerView
can reliably handle
Fragment
transactions and configuration changes. These may not work as
expected if you use the <fragment>
tag instead.
Retain instance usage
The retain instance usage violation is enabled using
detectRetainInstanceUsage()
and throws a
RetainInstanceUsageViolation
.
This violation indicates the usage of a retained Fragment
. Specifically, if
there are calls to
setRetainInstance()
or
getRetainInstance()
which are both deprecated.
Instead of using these methods to manage retained Fragment
instances
yourself, you should store state in a
ViewModel
that will handle this for you.
Set user visible hint
The set user visible hint violation is enabled using
detectSetUserVisibleHint()
and throws a
SetUserVisibleHintViolation
.
This violation indicates a call to
setUserVisibleHint()
,
which is deprecated.
If you are manually calling this method, then you should call
setMaxLifecycle()
instead. If you override this method, you should move the behavior to
onResume()
when passing in true
and
onPause()
when passing in false
.
Target fragment usage
The target fragment usage violation is enabled using
detectTargetFragmentUsage()
and throws a
TargetFragmentUsageViolation
.
This violation indicates a call to
setTargetFragment()
,
getTargetFragment()
,
or getTargetRequestCode()
,
which are all deprecated. Instead of using these methods you should register a
FragmentResultListener
. For more information, see Pass results between
fragments.
Wrong fragment container
The wrong fragment container violation is enabled using
detectWrongFragmentContainer()
and throws a
WrongFragmentContainerViolation
.
This violation indicates the addition of a Fragment
to a container other than
FragmentContainerView
. As with Fragment tag usage,
Fragment Transactions may not work as expected unless hosted inside a
FragmentContainerView
. It also helps address an issue in the View
API that
causes fragments using exit animations to be drawn on top of all other
fragments.