(#) Background colors with the same value should have the same 'on' color !!! ERROR: Background colors with the same value should have the same 'on' color This is an error. Id : `ConflictingOnColor` Summary : Background colors with the same value should have the same 'on' color Severity : Error Category : Correctness Platform : Any Vendor : Jetpack Compose Identifier : androidx.compose.material Feedback : https://issuetracker.google.com/issues/new?component=612128 Min : Lint 8.0 and 8.1 Compiled : Lint 8.7+ Artifact : [androidx.compose.material:material-android](androidx_compose_material_material-android.md.html) Since : 1.5.0 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:/compose/material/material-lint/src/main/java/androidx/compose/material/lint/ColorsDetector.kt) Tests : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/material/material-lint/src/test/java/androidx/compose/material/lint/ColorsDetectorTest.kt) Copyright Year : 2021 In the Material color system background colors have a corresponding 'on' color which is used for the content color inside a component. For example, a button colored `primary` will have `onPrimary` text. Because of this, it is important that there is only one possible `onColor` for a given color value, otherwise there is no way to know which 'on' color should be used inside a component. To fix this either use the same 'on' color for identical background colors, or use a different background color for each 'on' color. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/androidx/compose/material/foo/test.kt:15:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.White, ----------- src/androidx/compose/material/foo/test.kt:16:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.White, ----------- src/androidx/compose/material/foo/test.kt:17:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.White, ----------- src/androidx/compose/material/foo/test.kt:18:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.White, ----------- src/androidx/compose/material/foo/test.kt:19:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.Red, --------- src/androidx/compose/material/foo/test.kt:31:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.White, ----------- src/androidx/compose/material/foo/test.kt:32:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.Blue, ---------- src/androidx/compose/material/foo/test.kt:34:Error: Conflicting 'on' color for a given background [ConflictingOnColor] onSurface = Color.White, ----------- src/androidx/compose/material/foo/test.kt:51:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.White, ----------- src/androidx/compose/material/foo/test.kt:52:Error: Conflicting 'on' color for a given background [ConflictingOnColor] yellow400, --------- src/androidx/compose/material/foo/test.kt:53:Error: Conflicting 'on' color for a given background [ConflictingOnColor] Color.Blue, ---------- src/androidx/compose/material/foo/test.kt:55:Error: Conflicting 'on' color for a given background [ConflictingOnColor] yellow500, --------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/androidx/compose/material/foo/test.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers package androidx.compose.material.foo import androidx.compose.material.* import androidx.compose.ui.graphics.* val colors = Colors( Color.White, Color.White, Color.White, Color.White, Color.White, Color.White, Color.White, Color.White, Color.White, Color.White, Color.White, Color.Red, false ) val colors2 = Colors( primary = Color.White, Color.White, Color.White, Color.White, background = Color.Blue, Color.White, Color.Green, Color.White, Color.Blue, onBackground = Color.White, onSurface = Color.White, onError = Color.Red, isLight = false ) val yellow200 = Color(0xffffeb46) val yellow400 = Color(0xffffc000) val yellow500 = Color(0xffffde03) val colors3 = Colors( yellow200, yellow400, yellow200, secondaryVariant = yellow200, Color.White, surface = Color.Blue, Color.White, Color.White, yellow400, Color.Blue, onSurface = Color(0xFFFFBBCC), yellow500, false ) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/material/material-lint/src/test/java/androidx/compose/material/lint/ColorsDetectorTest.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, `ColorsDetector.constructorErrors_source`. 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.compose.material:material-android:1.8.0-alpha07") // build.gradle implementation 'androidx.compose.material:material-android:1.8.0-alpha07' // build.gradle.kts with version catalogs: implementation(libs.material.android) # libs.versions.toml [versions] material-android = "1.8.0-alpha07" [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: material-android = { module = "androidx.compose.material:material-android", version.ref = "material-android" } ``` 1.8.0-alpha07 is the version this documentation was generated from; there may be newer versions available. NOTE: These lint checks are **also** made available separate from the main library. You can also use `androidx.compose.material:material-lint:1.8.0-alpha07`. [Additional details about androidx.compose.material:material-android](androidx_compose_material_material-android.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("ConflictingOnColor") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("ConflictingOnColor") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection ConflictingOnColor 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="ConflictingOnColor" 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 'ConflictingOnColor' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore ConflictingOnColor ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).