(#) Use the 'require_____()' API rather than 'get____()' API for more descriptive error messages when it's null !!! ERROR: Use the 'require_____()' API rather than 'get____()' API for more descriptive error messages when it's null This is an error. Id : `UseRequireInsteadOfGet` Summary : Use the 'require_____()' API rather than 'get____()' API for more descriptive error messages when it's null Severity : Error Category : Correctness Platform : Any 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 : 1.2.2 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/UseRequireInsteadOfGet.kt) Tests : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/fragment/fragment-lint/src/test/java/androidx/fragment/lint/UseRequireInsteadOfGetTest.kt) Copyright Year : 2020 AndroidX added new "require____()" versions of common "get___()" APIs, such as getContext/getActivity/getArguments/etc. Rather than wrap these in something like requireNotNull(), using these APIs will allow the underlying component to try to tell you _why_ it was null, and thus yield a better error message. !!! Tip This lint check has an associated quickfix available in the IDE. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/foo/Test.java:10:Error: Use fragment.requireArguments() instead of checkNotNull(fragment.getArguments()) [UseRequireInsteadOfGet] checkNotNull(fragment.getArguments()); ------------------------------------- src/foo/Test.java:11:Error: Use fragment.requireFragmentManager() instead of checkNotNull(fragment.getFragmentManager()) [UseRequireInsteadOfGet] checkNotNull(fragment.getFragmentManager()); ------------------------------------------- src/foo/Test.java:12:Error: Use fragment.requireContext() instead of checkNotNull(fragment.getContext()) [UseRequireInsteadOfGet] checkNotNull(fragment.getContext()); ----------------------------------- src/foo/Test.java:13:Error: Use fragment.requireActivity() instead of checkNotNull(fragment.getActivity()) [UseRequireInsteadOfGet] checkNotNull(fragment.getActivity()); ------------------------------------ src/foo/Test.java:14:Error: Use fragment.requireHost() instead of checkNotNull(fragment.getHost()) [UseRequireInsteadOfGet] checkNotNull(fragment.getHost()); -------------------------------- src/foo/Test.java:15:Error: Use fragment.requireParentFragment() instead of checkNotNull(fragment.getParentFragment()) [UseRequireInsteadOfGet] checkNotNull(fragment.getParentFragment()); ------------------------------------------ src/foo/Test.java:16:Error: Use fragment.requireView() instead of checkNotNull(fragment.getView()) [UseRequireInsteadOfGet] checkNotNull(fragment.getView()); -------------------------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here are the relevant source files: `src/util/Preconditions.java`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers package util; public final class Preconditions { public static T checkNotNull(T value) { } public static T checkNotNull(T value, String message) { } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ `src/foo/Test.java`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers package foo; import androidx.fragment.app.Fragment; import static util.Preconditions.checkNotNull; class Test { void test() { Fragment fragment = new Fragment(); checkNotNull(fragment.getArguments()); checkNotNull(fragment.getFragmentManager()); checkNotNull(fragment.getContext()); checkNotNull(fragment.getActivity()); checkNotNull(fragment.getHost()); checkNotNull(fragment.getParentFragment()); checkNotNull(fragment.getView()); // These are redundant. Java-only really checkNotNull(fragment.requireArguments()); checkNotNull(fragment.requireFragmentManager()); checkNotNull(fragment.requireContext()); checkNotNull(fragment.requireActivity()); checkNotNull(fragment.requireHost()); checkNotNull(fragment.requireParentFragment()); checkNotNull(fragment.requireView()); // These don't have errors fragment.requireArguments(); fragment.requireFragmentManager(); fragment.requireContext(); fragment.requireActivity(); fragment.requireHost(); fragment.requireParentFragment(); fragment.requireView(); // These are ignored because they have custom error messages checkNotNull(fragment.getArguments(), "getArguments"); checkNotNull(fragment.getFragmentManager(), "getFragmentManager"); checkNotNull(fragment.getContext(), "getContext"); checkNotNull(fragment.getActivity(), "getActivity"); checkNotNull(fragment.getHost(), "getHost"); checkNotNull(fragment.getParentFragment(), "getParentFragment"); checkNotNull(fragment.getView(), "getView"); } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/fragment/fragment-lint/src/test/java/androidx/fragment/lint/UseRequireInsteadOfGetTest.kt) for the unit tests for this check to see additional scenarios. The above example was automatically extracted from the first unit test found for this lint check, `UseRequireInsteadOfGet.simple java checks where the fragment is a variable`. To report a problem with this extracted sample, visit https://issuetracker.google.com/issues/new?component=460964. (##) 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("UseRequireInsteadOfGet") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("UseRequireInsteadOfGet") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection UseRequireInsteadOfGet 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="UseRequireInsteadOfGet" 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 'UseRequireInsteadOfGet' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore UseRequireInsteadOfGet ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).