microg/GmsCore · error · UnsupportedOperationException

continueWith is not implemented

Error message

continueWith is not implemented

What it means

Task.continueWith(Continuation) is a stub in the base Task class that throws UnsupportedOperationException 'continueWith is not implemented'. Chaining a continuation onto Task completion is part of the API surface but unimplemented in this build unless the concrete Task class overrides it.

Source

Thrown at play-services-tasks/src/main/java/com/google/android/gms/tasks/Task.java:186

     * The listener will be automatically removed during {@link Activity#onStop()}.
     *
     * @return this Task
     */
    public abstract Task<TResult> addOnSuccessListener(Activity activity, OnSuccessListener<? super TResult> listener);


    /**
     * Returns a new Task that will be completed with the result of applying the specified
     * Continuation to this Task.
     * <p/>
     * The Continuation will be called on the main application thread.
     * <p/>
     * If the previous Task is canceled, the returned Task will also be canceled and the Continuation would not execute.
     *
     * @see Continuation#then(Task)
     */
    public <TContinuationResult> Task<TContinuationResult> continueWith(Continuation<TResult, TContinuationResult> continuation) {
        throw new UnsupportedOperationException("continueWith is not implemented");
    }

    /**
     * Returns a new Task that will be completed with the result of applying the specified Continuation to this Task.
     * <p/>
     * If the previous Task is canceled, the returned Task will also be canceled and the Continuation would not execute.
     *
     * @param executor the executor to use to call the Continuation
     * @see Continuation#then(Task)
     */
    public <TContinuationResult> Task<TContinuationResult> continueWith(Executor executor, Continuation<TResult, TContinuationResult> continuation) {
        throw new UnsupportedOperationException("continueWith is not implemented");
    }

    /**
     * Returns a new Task that will be completed with the result of applying the specified
     * Continuation to this Task.
     * <p/>

View on GitHub (pinned to 157c9d86ac)

Solutions

  1. Upgrade to a library version implementing continueWith
  2. Restructure to use addOnCompleteListener + manual result transformation if that overload is implemented
  3. Use Tasks.await(task) then apply the continuation synchronously
  4. Catch UnsupportedOperationException and apply the Continuation manually after completion

Example fix

// before
Task<String> next = task.continueWith(continuation); // throws
// after
String result = continuation.then(Tasks.await(task)); // synchronous fallback
Defensive patterns

Strategy: try-catch

Try / catch

try {
    Task<R> next = task.continueWith(continuation);
} catch (UnsupportedOperationException e) {
    R result = continuation.then(Tasks.await(task));
}

Prevention

When it happens

Trigger: Chaining follow-up work with continueWith(continuation) on a Task using the base implementation.

Common situations: Functional-style Task chaining ported from Google Play Services / gms tasks code; the library port omits the override so all chaining calls fail.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of microg/GmsCore@157c9d86ac (2026-09-06). Data as JSON: /api/errors/32d8f063dfbac73c. Report an issue: GitHub.