CODEWITHSUNDEEP
kotlincollectionsandroid-cameraandroid-camera2
portfoliobuilder
portfoliobuilder

Reputation: 7856

Immutable Collection Treated as Mutable. Cannot use Collections.max

I am working with Camera2 API, and I am trying to retrieve the largest available image size. I want to use Collections.max. I have tried to write this code in Java, and it works fine.

JAVA Ex-

CameraCharacteristics characteristics
                    = manager.getCameraCharacteristics(cameraId);

            // We don't use a front facing camera in this sample.
            Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);
            if (facing != null && facing == CameraCharacteristics.LENS_FACING_FRONT) {
                continue;
            }

            StreamConfigurationMap map = characteristics.get(
                    CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            if (map == null) {
                continue;
            }

            // For still image captures, we use the largest available size.
            Size largest = Collections.max(
                    Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),
                    new CompareSizesByArea());

However, the Kotlin equivalent has an issue with the Collections.max operation.

Kotlin Ex-

val characteristics = manager.getCameraCharacteristics(cameraId)

                val map = characteristics.get(
                    CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP
                ) ?: continue

    // for still image captures, we use the largest available size
                    val largest = Collections.max(
                        listOf(map.getOutputSizes(ImageFormat.JPEG)),
                        CompareSizesByArea()
                    )

The error says,

None of the following substitutions ((MutableCollection<out Array<(out) Size!>!>..Collection<Array<(out) Size!>!>?),Comparator<in Array<(out) Size!>!>!) ((MutableCollection<out Size!>..Collection<Size!>?),Comparator<in Size!>!) can be applied to (List<Array<(out) Size!>!>,CompareSizesByArea)

I am not sure how to correct my code. I can use Collections.max in other instances, such as

val test = listOf(1,2,3,4,3,2,1)
Collections.max(test)

The issue is the map of output sizes??

Upvotes: 0

Views: 129

Answers (1)

Tenfour04
Tenfour04

Reputation: 93581

Arrays.asList(), as you used in your Java code, converts an array to a List. So you have a List<Size>.

listOf(), as you used in your Kotlin code, creates a list of the items you pass to it. In this case, you pass a single item to it, an array. So you are creating a List<Array<Size>> with a single object in it, the array of sizes.

The equivalent way to do Arrays.asList() in Kotlin is to simply call .asList() on the array:

val largest = Collections.max(
        map.getOutputSizes(ImageFormat.JPEG).asList(),
        CompareSizesByArea()
    )

But if you're going to do it purely in Kotlin, you can skip the Collections function and do this more simply:

val largest = map.getOutputSizes(ImageFormat.JPEG).maxBy { it.width * it.height }

Upvotes: 2

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