(#) Incorrect `WakeLock` usage !!! WARNING: Incorrect `WakeLock` usage This is a warning. Id : `Wakelock` Summary : Incorrect `WakeLock` usage Severity : Warning Category : Performance Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : Initial Affects : Kotlin and Java files Editing : This check runs on the fly in the IDE editor 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/WakelockDetector.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/WakelockDetectorTest.kt) Copyright Year : 2012 Failing to release a wakelock properly can keep the Android device in a high power mode, which reduces battery life. There are several causes of this, such as releasing the wake lock in `onDestroy()` instead of in `onPause()`, failing to call `release()` in all possible code paths after an `acquire()`, and so on. NOTE: If you are using the lock just to keep the screen on, you should strongly consider using `FLAG_KEEP_SCREEN_ON` instead. This window flag will be correctly managed by the platform as the user moves between applications and doesn't require a special permission. See https://developer.android.com/reference/android/view/WindowManager.LayoutParams.html#FLAG_KEEP_SCREEN_ON. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/test/pkg/WakelockActivity3.java:13:Warning: The release() call is not always reached (because of a possible exception in the path acquire() → randomCall() → exit; use try/finally to ensure release is always called) [Wakelock] lock.release(); // Should be in finally block ------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/test/pkg/WakelockActivity3.java`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers package test.pkg; import android.app.Activity; import android.os.PowerManager; public class WakelockActivity3 extends Activity { void wrongFlow() { PowerManager manager = (PowerManager) getSystemService(POWER_SERVICE); PowerManager.WakeLock lock = manager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "Test"); lock.acquire(); randomCall(); lock.release(); // Should be in finally block } static void randomCall() { System.out.println("test"); } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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/WakelockDetectorTest.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("Wakelock") fun method() { acquire(...) } ``` or ```java // Java @SuppressWarnings("Wakelock") void method() { acquire(...); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection Wakelock 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="Wakelock" 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 'Wakelock' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore Wakelock ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).