(#) Usage of KeyEvent.KEYCODE_BACK !!! WARNING: Usage of KeyEvent.KEYCODE_BACK This is a warning. Id : `GestureBackNavigation` Summary : Usage of KeyEvent.KEYCODE_BACK Severity : Warning Category : Correctness Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : 7.4.0 (January 2023) Affects : Kotlin and Java files Editing : This check runs on the fly in the IDE editor See : https://developer.android.com/guide/navigation/custom-back/predictive-back-gesture Implementation : [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/GestureBackNavDetector.kt) Tests : [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/GestureBackNavDetectorTest.kt) For apps targeting and running on Android 16+ (API 36+), predictive back animations are enabled by default. A back gesture does not trigger `{Activity,Dialog}.onBackPressed`, and does not dispatch `KeyEvent.KEYCODE_BACK`. Apps should migrate to AndroidX's backward compatible `OnBackPressedDispatcher`. This lint check does not consider per-activity opt-in/opt-out, so you may need to suppress or baseline reported incidents if migrating per-activity. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/test/pkg/KeyEventKeyCodeBackTest.java:17:Warning: onBackPressed is no longer called for back gestures; migrate to AndroidX's backward compatible OnBackPressedDispatcher [GestureBackNavigation] public void onBackPressed() { ------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here are the relevant source files: `src/AndroidManifest.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="test.pkg"> <uses-sdk android:minSdkVersion="24" android:targetSdkVersion="35" /> <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:enableOnBackInvokedCallback="true" > <activity android:name=".KeyEventKeyCodeBackTest" android:label="@string/app_name" android:exported="true" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ `src/test/pkg/KeyEventKeyCodeBackTest.java`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers package test.pkg; import android.app.Activity; import android.content.Context; import android.view.KeyEvent; @SuppressWarnings("unused") public class KeyEventKeyCodeBackTest extends Activity { public boolean onKeyUp(int keyCode, KeyEvent event) { if (KeyEvent.KEYCODE_BACK == keyCode) { return true; } } @Override public void onBackPressed() { // handle back } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/GestureBackNavDetectorTest.kt) for the unit tests for this check to see additional scenarios. (##) 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("GestureBackNavigation") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("GestureBackNavigation") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection GestureBackNavigation 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="GestureBackNavigation" 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 'GestureBackNavigation' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore GestureBackNavigation ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).