(#) Missing Firebase Messaging Callback !!! WARNING: Missing Firebase Messaging Callback This is a warning. Id : `MissingFirebaseInstanceTokenRefresh` Summary : Missing Firebase Messaging Callback Severity : Warning Category : Correctness Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : 2.3.0 (March 2017) Affects : Kotlin and Java files Editing : This check runs on the fly in the IDE editor See : https://firebase.google.com/docs/cloud-messaging/android/client#monitor-token-generation 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/FirebaseMessagingDetector.java) 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/FirebaseMessagingDetectorTest.java) Apps that use Firebase Cloud Messaging should implement the `FirebaseMessagingService#onNewToken()` callback in order to observe token changes. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/com/google/firebase/samples/messaging/advanced/services/MessagingService.java:5:Warning: Apps that use Firebase Cloud Messaging should implement onNewToken() in order to observe token changes [MissingFirebaseInstanceTokenRefresh] public class MessagingService extends FirebaseMessagingService { ---------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/com/google/firebase/samples/messaging/advanced/services/MessagingService.java`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers package com.google.firebase.samples.messaging.advanced.services; import com.google.firebase.messaging.FirebaseMessagingService; public class MessagingService extends FirebaseMessagingService { } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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/FirebaseMessagingDetectorTest.java) 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, `FirebaseMessagingDetector.testMissing`. To report a problem with this extracted sample, visit https://issuetracker.google.com/issues/new?component=192708. (##) 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("MissingFirebaseInstanceTokenRefresh") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("MissingFirebaseInstanceTokenRefresh") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection MissingFirebaseInstanceTokenRefresh 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="MissingFirebaseInstanceTokenRefresh" 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 'MissingFirebaseInstanceTokenRefresh' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore MissingFirebaseInstanceTokenRefresh ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).