I'm trying to wrap a java method from the android ...

# coroutines

[Christopher Mederos]

I'm trying to wrap a java method from the android sdk in a coroutine. Interestingly, the java method executes a task but only invokes the callback on success. Does this mean I should also wrap it in a timeout? Is there another means to know the underlying task completed even it doesn't invoke my callback?

suspendCancellableCoroutine { continuation ->
    MyJavaTaskWithCallback() { myValueOnlyOnSuccess ->
        continuation.resume(myValueOnlyOnSuccess)
    }
}

[Christopher Mederos]

The actual android method - only runs callback if the scanner finds any paths

public static void scanFile(Context context, String[] paths, String[] mimeTypes,
    OnScanCompletedListener callback) {
BackgroundThread.getExecutor().execute(() -> {
    try (ContentProviderClient client = context.getContentResolver()
            .acquireContentProviderClient(MediaStore.AUTHORITY)) {
        for (String path : paths) {
            final Uri uri = scanFileQuietly(client, new File(path));
            runCallBack(context, callback, path, uri);
        }
    }
});
}

[Sam]

only invokes the callback on success

Are you sure? My reading of the code is that the callback will always be called exactly once for each item in the paths array, regardless of success or failure. In that case, you can just count the callbacks and stop when you've had the expected number. Are you seeing something different from that when you run the code?

[Sam]

I think you could do something like this:

[Sam]

suspend fun scan(context: Context, paths: Array<String>): Map<String, Uri?> {
  val results = callbackFlow {
    MediaScannerConnection.scanFile(context, paths, null) { path, uri ->
      trySend(path to uri)
    }
  }
  return results.take(paths.size).toList().toMap()
}