Run multiple HTTP requests in multiple threads in Kotlin Android

Question

I have a listener where the user can send a POST HTTP request, but I want to let the user send as many HTTP requests as possible (He won't have to wait for the HTTP request to end), but I am not sure about whether to use Coroutines or threads. So I need to be pointed into documentation that provides a context for what I want to do. Here is my code, where the target function to run in a thread is uploadFile:

            ...
            findViewById<View>(R.id.screen).setOnClickListener { _: View? ->
            imgCap.takePicture(object : ImageCapture.OnImageCapturedListener() {
                override fun onCaptureSuccess(image: ImageProxy, rotationDegrees: Int) {
                    i += 1;
                    Log.i("Click", "Click number $i");
                    Toast.makeText(baseContext, "Image Captured", Toast.LENGTH_SHORT).show()
                    uploadFile(image)
                    super.onCaptureSuccess(image, rotationDegrees)
                }
            })
        }
        CameraX.bindToLifecycle(this, preview, imgCap)
    }
    private fun uploadFile(img: ImageProxy) {
        val url = "https://5d6d-41-97-171-237.eu.ngrok.io/api/photos"
        val bitmap = img.convertImageProxyToBitmap()
        Log.e("bitmap", bitmap.toString())
        val imgBase = convertImageToBase64(bitmap)

        val bos = ByteArrayOutputStream()
        bitmap.compress(Bitmap.CompressFormat.JPEG, 75, bos)


        // add parameter
        val formBody = FormBody.Builder().add("photo", imgBase).build()


        // creating request
        var request = Request.Builder().url(url)
            .post(formBody)
            .build()

        var client = OkHttpClient();
        client.newCall(request).enqueue(object : Callback {
            override fun onResponse(call: Call, response: Response) {
                println(response.body?.string())

            }

            override fun onFailure(call: Call, e: IOException) {
                Log.e("Exception:", e.toString())
                Log.e("Error:", e.message.toString())
            }
        })
    }

Workmanager may be? developer.android.com/topic/libraries/architecture/workmanager — Andrew
– Andrew, Commented Oct 16, 2022 at 12:35

Sergio · Accepted Answer · 2022-10-16 12:44:02Z

Kotlin Coroutines can be used for that:

// making function `suspend` to suspend a coroutine 
// and execute other code after that if need
private suspend fun uploadFile(img: ImageProxy) = suspendCoroutine { continuation ->
    // ... initialize request

    var client = OkHttpClient();
    client.newCall(request).enqueue(object : Callback {
            override fun onResponse(call: Call, response: Response) {
                println(response.body?.string())
                continuation.resume(response) // resumes the coroutine
            }
    
            override fun onFailure(call: Call, e: IOException) {
                Log.e("Exception:", e.toString())
                Log.e("Error:", e.message.toString())
                continuation.resume(null)    // resumes the coroutine
                // or continuation.resumeWithException(e)
            }
        })
}

// call this function instead of `uploadFile()`
private fun upload(img: ImageProxy) {
    // launch-and-forget coroutine
    lifecycleScope.launch {
        uploadFile(img)
        // do something after file is uploaded
    }
}

suspendCoroutine builder was used here to convert an api function with callback into a suspend function.

Arka-cell · Accepted Answer · 2022-10-19 17:45:19Z

0

After delving into more into the application, I had to set a lower resolution on the ImageCaptureConfig builder with setTargetResolution(resolution).

I started doing multiple requests at the same time, and it seems that the Event Listener on the view is acting asynchronously, managing to perform a request after a request without waiting for the first request to finish uploading the file. There are some limitations, and that's due to hardware that I'm looking into. But the code I was using works perfectly as I wanted to after I was able to notice uploads on shorter timescales.

answered Oct 19, 2022 at 17:45

Arka-cell

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