android - AndroidでCRONETを使用して「マルチパート/フォームデータ」POSTを送信するには?

Question

CRONET を使用して Android で multipart/form-data POST を送信できた人はいますか? サーバーへの POST リクエストを使用して画像/png をアップロードしようとしても成功しませんでした。

メモ : CRONET ベースのソリューションのみが必要です

Post メソッドの例:

val myBuilder = CronetEngine.Builder(context)
// Enable caching of HTTP data and
// other information like QUIC server information, HTTP/2 protocol and QUIC protocol.
val cronetEngine: CronetEngine = myBuilder
    .enableHttpCache(CronetEngine.Builder.HTTP_CACHE_IN_MEMORY, 100 * 1024.toLong())
    .enableHttp2(true)
    .enableQuic(true)
    .build()
val executor: Executor = Executors.newSingleThreadExecutor()
val requestBuilder = cronetEngine.newUrlRequestBuilder(
    "FULL-URL",
    MyUrlRequestCallback(),
    executor
)
// Content-Type is required, removing it will cause Exception
requestBuilder.addHeader("Content-Type","application/json; charset=UTF-8")
requestBuilder.setHttpMethod("POST")
val myUploadDataProvider = MyUploadDataProvider()
requestBuilder.setUploadDataProvider(myUploadDataProvider,executor)
val request: UrlRequest = requestBuilder.build()
request.start()

MyUploadDataProvider クラス:

import android.util.Log
import org.chromium.net.UploadDataProvider
import org.chromium.net.UploadDataSink
import java.lang.Exception
import java.nio.ByteBuffer
import java.nio.charset.StandardCharsets

private const val TAG = "MyUploadDataProvider"
//TODO replace username and passowrd "_user & _pass"
var string: String ="{\"username\":\"_user\",\"password\":\"_pass\"}"
val charset = StandardCharsets.UTF_8

class MyUploadDataProvider() : UploadDataProvider() {

    override fun getLength(): Long {
    val size:Long = string.length.toLong()
    Log.e(TAG,"Length = "+size)
    return size
    }

    override fun rewind(uploadDataSink: UploadDataSink?) {
    Log.e(TAG,"REWIND IS CALLED")
    uploadDataSink!!.onRewindSucceeded()
    }

    override fun read(uploadDataSink: UploadDataSink?, byteBuffer: ByteBuffer?) {
    Log.e(TAG,"READ IS CALLED")
    byteBuffer!!.put(string.toByteArray(charset))
    //byteBuffer.rewind()
    //For chunked uploads, true if this is the final read. It must be false for non-chunked uploads.
    uploadDataSink!!.onReadSucceeded(false)
    }

}