ImageOperations.kt

/*
 * Copyright 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.background


/**
 * Builds and holds WorkContinuation based on supplied filters.
 */
@SuppressLint("EnqueueWork")
class ImageOperations(
    /* params removed */
) {

    //..
    //Add some DummyWorkers to continuation in init()
    init {
        continuation = WorkManager.getInstance(context)
            .beginUniqueWork(
                Constants.IMAGE_MANIPULATION_WORK_NAME,
                ExistingWorkPolicy.REPLACE,
                OneTimeWorkRequest.from(CleanupWorker::class.java)
            )
            //Add 2 DummyWorker 
            .then(
                listOf(
                    OneTimeWorkRequest.from(DummyWorker::class.java),
                    OneTimeWorkRequest.from(DummyWorker::class.java))
            )
            .thenMaybe<WaterColorFilterWorker>(waterColor)
            //Add 4 more workers here
            .then(listOf(
                OneTimeWorkRequest.from(DummyWorker::class.java),
                OneTimeWorkRequest.from(DummyWorker::class.java),
                OneTimeWorkRequest.from(DummyWorker::class.java),
                OneTimeWorkRequest.from(DummyWorker::class.java)))
            .thenMaybe<GrayScaleFilterWorker>(grayScale)
            .thenMaybe<BlurEffectFilterWorker>(blur)
            .then(
                if (save) {
                    workRequest<SaveImageToGalleryWorker>(tag = Constants.TAG_OUTPUT)
                } else /* upload */ {
                    workRequest<UploadWorker>(tag = Constants.TAG_OUTPUT)
                }
            )
            //Another 2 DummyWorker here
            .then(listOf(
                OneTimeWorkRequest.from(DummyWorker::class.java),
                OneTimeWorkRequest.from(DummyWorker::class.java)))
    }

  //...
}