• android
    @Retention(value = AnnotationRetention.BINARY)
    @Target(allowedTargets = [AnnotationTarget.ANNOTATION_CLASS])
    annotation RequiresOptIn

Denotes that the annotated element is a marker of an opt-in API.

Any declaration annotated with this marker is considered part of an unstable or otherwise non-standard API surface and its call sites should accept the opt-in aspect of it either by using OptIn or by being annotated with that marker themselves, effectively causing further propagation of that opt-in aspect.

// Marker definition

@Retention(CLASS)
@Target({TYPE, METHOD, CONSTRUCTOR, FIELD, PACKAGE})
@RequiresOptIn(level = Level.ERROR)
public @interface ExperimentalDateTime {}

@ExperimentalDateTime
public class DateProvider {
  // ...
}

// Client code

int getYear() {
  DateProvider provider; // Error: DateProvider is experimental
  // ...
}

@ExperimentalDateTime
Date getDate() {
  DateProvider provider; // OK: the function is marked as experimental
  // ...
}

void displayDate() {
  System.out.println(getDate()); // Error: getDate() is experimental, acceptance is required
}

To configure project-wide opt-in, specify the opt-in option value in lint.xml as a comma-delimited list of opted-in annotations:

<lint>
  <issue id="$issueId">
    <option name="opt-in" value="com.foo.ExperimentalBarAnnotation" />
  </issue>
</lint>

Summary

Nested types

Severity of the diagnostic that should be reported on usages of opt-in API which did not explicitly accept the opt-in aspect of that API either by:

Public constructors
android

Public properties
RequiresOptIn.Level

Defines the reporting level for incorrect usages of this opt-in API.
android
String

Message to be reported on usages of API without an explicit opt-in, or empty string for the default message.
android

Public constructors

RequiresOptIn

android 
RequiresOptIn(level: RequiresOptIn.Level = Level.ERROR, message: String = "")

Public properties

level

android 
val level: RequiresOptIn.Level

Defines the reporting level for incorrect usages of this opt-in API.

message

android 
val message: String

Message to be reported on usages of API without an explicit opt-in, or empty string for the default message. The default message is: "This declaration is experimental and its usage should be marked with 'Marker' or '@OptIn(Marker::class)'", where Marker is the opt-in requirement marker.