CameraBarcodePreviewView.kt

package com.paragoncoin.paragon.core.ui.view

import android.Manifest
import android.annotation.SuppressLint
import android.app.Activity
import android.content.Context
import android.util.AttributeSet
import android.view.SurfaceHolder
import android.view.SurfaceView
import android.view.ViewGroup
import androidx.annotation.RequiresPermission
import com.google.android.gms.vision.CameraSource
import com.google.android.gms.vision.MultiProcessor
import com.google.android.gms.vision.barcode.Barcode
import com.google.android.gms.vision.barcode.BarcodeDetector
import com.paragoncoin.paragon.core.domain.barcode.BarcodeTrackerFactory
import java.io.IOException

@SuppressLint("MissingPermission")
class CameraBarcodePreviewView @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyleAttr: Int = 0
) : ViewGroup(context, attrs, defStyleAttr) {

    private var cameraSource: CameraSource? = null
    private var barcodeCallback: ((Barcode) -> Unit)? = null
    private var surfaceAvailable = false
    private val surfaceCallback = object : SurfaceHolder.Callback {
        override fun surfaceChanged(holder: SurfaceHolder, format: Int, width: Int, height: Int) {
        }

        override fun surfaceCreated(holder: SurfaceHolder) {
            refresh()
        }

        override fun surfaceDestroyed(holder: SurfaceHolder) {
            surfaceAvailable = false
        }
    }

    private val surfaceView = SurfaceView(context)
    private val holder get() = surfaceView.holder

    private var startedByUser = false

    init {
        addView(surfaceView)
        holder.addCallback(surfaceCallback)
        holder.setSizeFromLayout()
    }

    override fun onLayout(changed: Boolean, left: Int, top: Int, right: Int, bottom: Int) {
        val layoutWidth = right - left
        val layoutHeight = bottom - top

        // calculate surface view layout to avoid deformed picture
        val (width, height) = cameraSource
                ?.takeUnless { it.previewSize == null }
                ?.let { source ->
                    val (previewWidth, previewHeight) = with(source.previewSize) { height to width }

                    return@let if (previewHeight * layoutWidth / previewWidth > layoutHeight) {
                        layoutWidth to (previewHeight * layoutWidth / previewWidth)
                    } else (previewWidth * layoutHeight / previewHeight) to layoutHeight

                } ?: layoutWidth to layoutHeight


        for (i in 0 until childCount) {
            getChildAt(i).layout(0, 0, width, height)
        }

        startInternal()
    }

    @RequiresPermission(Manifest.permission.CAMERA)
    fun start() {
        startedByUser = true
        startInternal()
    }

    fun stop() {
        cameraSource?.stop()
    }

    fun release() = releaseSource()

    fun onBarcodeDetected(handler: (Barcode) -> Unit) {
        barcodeCallback = handler
    }

    fun startWithRefresh() {
        refresh()
        start()
    }

    private fun refresh() {
        surfaceAvailable = true
        refreshCamera()
        requestLayout()
    }

    private fun startInternal() {
        if (startedByUser) try {
            if (surfaceAvailable) cameraSource?.start(holder)
        } catch (e: IOException) {
            releaseSource()
        }
    }

    private fun releaseSource() {
        try {
            cameraSource?.release()
        } catch (thr: Throwable) {
        }
    }

    @RequiresPermission(Manifest.permission.CAMERA)
    private fun refreshCamera() {
        releaseSource()
        cameraSource = createCameraSource()
        startInternal()
    }

    private fun onBarcodeDetected(barcode: Barcode) {
        (context as? Activity)?.runOnUiThread {
            barcodeCallback?.invoke(barcode)
        }
    }

    @RequiresPermission(Manifest.permission.CAMERA)
    private fun createCameraSource() = CameraSource.Builder(context.applicationContext,
            BarcodeDetector.Builder(context).build().apply {
                setProcessor(MultiProcessor.Builder(
                        BarcodeTrackerFactory(::onBarcodeDetected)
                ).build())
            })
            .setFacing(CameraSource.CAMERA_FACING_BACK)
            .setRequestedPreviewSize(1600, 1024)
            .setRequestedFps(15.0f)
            .setAutoFocusEnabled(true)
            .build()

}