(#) You must call collect on the given progress flow when using PredictiveBackHandler !!! ERROR: You must call collect on the given progress flow when using PredictiveBackHandler This is an error. Id : `NoCollectCallFound` Summary : You must call collect on the given progress flow when using PredictiveBackHandler Severity : Error Category : Correctness Platform : Any Vendor : Jetpack Activity Compose Identifier : androidx.activity.compose Feedback : https://issuetracker.google.com/issues/new?component=612128 Min : Lint 8.0 and 8.1 Compiled : Lint 8.7+ Artifact : [androidx.activity:activity-compose](androidx_activity_activity-compose.md.html) Since : 1.8.0 Affects : Kotlin and Java files and test sources Editing : This check runs on the fly in the IDE editor Implementation : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/activity/activity-compose-lint/src/main/java/androidx/activity/compose/lint/CollectProgressDetector.kt) Tests : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/activity/activity-compose-lint/src/test/java/androidx/activity/compose/lint/CollectProgressDetectorTest.kt) Copyright Year : 2023 You must call collect on the progress in the onBack function. The collect call is what properly splits the callback so it knows what to do when the back gestures is started vs when it is completed. Failing to call collect will cause all code in the block to run when the gesture is started. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/com/example/test.kt:9:Error: You must call collect() on Flow progress [NoCollectCallFound] PredictiveBackHandler { progress -> } -------- src/com/example/test.kt:13:Error: You must call collect() on Flow progress [NoCollectCallFound] PredictiveBackHandler { progress -> } -------- src/com/example/test.kt:17:Error: You must call collect() on Flow progress [NoCollectCallFound] PredictiveBackHandler { progress -> } -------- src/com/example/test.kt:26:Error: You must call collect() on Flow progress [NoCollectCallFound] PredictiveBackHandler { progress -> } -------- src/com/example/test.kt:29:Error: You must call collect() on Flow progress [NoCollectCallFound] PredictiveBackHandler { progress -> } -------- src/com/example/test.kt:35:Error: You must call collect() on Flow progress [NoCollectCallFound] PredictiveBackHandler { progress -> } -------- src/com/example/test.kt:39:Error: You must call collect() on Flow progress [NoCollectCallFound] PredictiveBackHandler { progress -> } -------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/com/example/test.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers package com.example import androidx.compose.runtime.Composable import androidx.activity.compose.PredictiveBackHandler @Composable fun Test() { PredictiveBackHandler { progress -> } } val lambda = @Composable { PredictiveBackHandler { progress -> } } val lambda2: @Composable () -> Unit = { PredictiveBackHandler { progress -> } } @Composable fun LambdaParameter(content: @Composable () -> Unit) {} @Composable fun Test2() { LambdaParameter(content = { PredictiveBackHandler { progress -> } }) LambdaParameter { PredictiveBackHandler { progress -> } } } fun test3() { val localLambda1 = @Composable { PredictiveBackHandler { progress -> } } val localLambda2: @Composable () -> Unit = { PredictiveBackHandler { progress -> } } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/activity/activity-compose-lint/src/test/java/androidx/activity/compose/lint/CollectProgressDetectorTest.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, `CollectProgressDetector.errors`. To report a problem with this extracted sample, visit https://issuetracker.google.com/issues/new?component=612128. (##) Including !!! This is not a built-in check. To include it, add the below dependency to your project. ``` // build.gradle.kts implementation("androidx.activity:activity-compose:1.11.0-rc01") // build.gradle implementation 'androidx.activity:activity-compose:1.11.0-rc01' // build.gradle.kts with version catalogs: implementation(libs.activity.compose) # libs.versions.toml [versions] activity-compose = "1.11.0-rc01" [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: activity-compose = { module = "androidx.activity:activity-compose", version.ref = "activity-compose" } ``` 1.11.0-rc01 is the version this documentation was generated from; there may be newer versions available. [Additional details about androidx.activity:activity-compose](androidx_activity_activity-compose.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("NoCollectCallFound") fun method() { PredictiveBackHandler(...) } ``` or ```java // Java @SuppressWarnings("NoCollectCallFound") void method() { PredictiveBackHandler(...); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection NoCollectCallFound 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="NoCollectCallFound" 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 'NoCollectCallFound' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore NoCollectCallFound ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).