(#) Separate attach() and detach() into separate FragmentTransactions !!! WARNING: Separate attach() and detach() into separate FragmentTransactions This is a warning. Id : `DetachAndAttachSameFragment` Summary : Separate attach() and detach() into separate FragmentTransactions Severity : Warning Category : Correctness Platform : Android Vendor : Android Open Source Project Identifier : androidx.fragment Feedback : https://issuetracker.google.com/issues/new?component=460964 Min : Lint 7.0 Compiled : Lint 8.0 and 8.1 Artifact : [androidx.fragment:fragment](androidx_fragment_fragment.md.html) Since : 1.4.0 Affects : Kotlin and Java files Editing : This check runs on the fly in the IDE editor Implementation : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/fragment/fragment-lint/src/main/java/androidx/fragment/lint/AttachAndDetachInSameTransactionDetector.kt) Tests : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/fragment/fragment-lint/src/test/java/androidx/fragment/lint/AttachAndDetachInSameTransactionDetectorTest.kt) Copyright Year : 2019 When doing a FragmentTransaction that includes both attach() and detach() operations being committed on the same fragment instance, it is a no-op. The reason for this is that the FragmentManager optimizes all operations within a single transaction so the attach() and detach() cancel each other out and neither is actually executed. To get the desired behavior, you should separate the attach() and detach() calls into separate FragmentTransactions. (##) Including !!! This is not a built-in check. To include it, add the below dependency to your project. ``` // build.gradle.kts implementation("androidx.fragment:fragment:1.8.6") // build.gradle implementation 'androidx.fragment:fragment:1.8.6' // build.gradle.kts with version catalogs: implementation(libs.fragment) # libs.versions.toml [versions] fragment = "1.8.6" [libraries] # For clarity and text wrapping purposes the following declaration is # shown split up across lines, but in TOML it needs to be on a single # line (see https://github.com/toml-lang/toml/issues/516) so adjust # when pasting into libs.versions.toml: fragment = { module = "androidx.fragment:fragment", version.ref = "fragment" } ``` 1.8.6 is the version this documentation was generated from; there may be newer versions available. [Additional details about androidx.fragment:fragment](androidx_fragment_fragment.md.html). (##) Suppressing You can suppress false positives using one of the following mechanisms: * Using a suppression annotation like this on the enclosing element: ```kt // Kotlin @Suppress("DetachAndAttachSameFragment") fun method() { beginTransaction(...) } ``` or ```java // Java @SuppressWarnings("DetachAndAttachSameFragment") void method() { beginTransaction(...); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection DetachAndAttachSameFragment problematicStatement() ``` * Using a special `lint.xml` file in the source tree which turns off the check in that folder and any sub folder. A simple file might look like this: ```xml <?xml version="1.0" encoding="UTF-8"?> <lint> <issue id="DetachAndAttachSameFragment" severity="ignore" /> </lint> ``` Instead of `ignore` you can also change the severity here, for example from `error` to `warning`. You can find additional documentation on how to filter issues by path, regular expression and so on [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html). * In Gradle projects, using the DSL syntax to configure lint. For example, you can use something like ```gradle lintOptions { disable 'DetachAndAttachSameFragment' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore DetachAndAttachSameFragment ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).