Printer module

Call flow

It is rather simple to print receipts or reports using the built-in printer in APOLLO.

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Setup

Create an instance and connect the app to the terminal by getControllerInstance() and connectController().

The app shall be notified by onError if there's any errors occurred.

abstract class ApolloPrinter(private val context: Context) : PrinterDelegate {

    private var printerController: PrinterController? = null
    private val printerFixedWidth = 384
    private lateinit var printData: ByteArray

    fun connect(): Boolean {
        try {
            if (printerController == null) {
                // get instance
                printerController = getControllerInstance(context, this)

                // enable debug log display in console
                SPDeviceController.enableDebugLog(true)
            }
            // establish the communication channel with terminal
            printerController?.connectController()
        } catch (ex: Exception) {
            return false
        }
        return true
    }

    fun disconnect() {
        printerController?.disconnectController()
        printerController?.releaseControllerInstance()
    }

    override fun onError(errorType: ControllerError.Error?, message: String?) {
        // handle error here
    }

}

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Printing flow

Prepare printData

The APOLLO thermal printer has 384 dots/ line. The app should convert the receipt or report to byte array before sending to the printer.

A simple approach is first create the receipt or report in HTML and convert it to bitmap. On the app build.gradle, add the html2bitmap dependency.

dependencies {
  //HTML to bitmap library
  implementation 'com.izettle:html2bitmap:1.6'
}

In ApolloPrinter class, there's an example for converting bitmap to ByteArray.

/**
 * Input bitmap can be any size but preferred use APOLLO printer width or scaling is needed
 */
private fun bitmapTo1bppByteArray(bitmap: Bitmap): ByteArray {
    val bFilter = true
    val bmpResult: Bitmap

    var width = bitmap.width
    var height = bitmap.height
    val widthNew = printerFixedWidth
    val dataLen = ceil((width * height).toDouble() / 8).toInt()
    val paddedData = ByteArray(dataLen)

    /* First do a scale to make sure width match apollo criteria */
    if (widthNew != bitmap.width) {
        val scaleWidthFactor = widthNew.toDouble() / width
        val dstHeight = (height * scaleWidthFactor).toInt()
        bmpResult = Bitmap.createScaledBitmap(bitmap, widthNew, dstHeight, bFilter)
    } else {
        bmpResult = bitmap
    }

    //Change to B&W and RGB565
    val convertedBitmap = Bitmap.createBitmap(bmpResult.width, bmpResult.height, Bitmap.Config.RGB_565)
    val canvas = Canvas(convertedBitmap)
    val ma = ColorMatrix()
    ma.setSaturation(0f)
    val paint = Paint()
    paint.colorFilter = ColorMatrixColorFilter(ma)
    canvas.drawBitmap(bitmap, 0f, 0f, paint)

    width = convertedBitmap.width
    height = convertedBitmap.height

    val bb: ByteBuffer = ByteBuffer.allocate(convertedBitmap.byteCount)
    convertedBitmap.copyPixelsToBuffer(bb)

    val byteStream = ByteArrayInputStream(bb.array())

    var bitPosition = 0
    var bytePosition = 0

    for (y in 0 until height) {
        for (x in 0 until width) {
            //Read 2 bytes from byte stream, beware of endian
            val rgb565 = byteStream.read() or (byteStream.read() shl 8)

            //Here for simplicity just use Red value (5bits) and threshold set to 16 which assume the input bitmap already in Grey scale
            val red = (rgb565 shr 11)

            //get binary value
            var value: Byte

            value = if (red <= 16) {
                0x01.toByte()
            } else {
                0x00.toByte()
            }

            paddedData[bytePosition] = paddedData[bytePosition] or (value.toInt() shl bitPosition).toByte()
            bitPosition++

            if (bitPosition == 8) {
                bitPosition = 0
                bytePosition++
            }
        }
    }

    return paddedData
}

You can convert the bitmap to byteArray by bitmapTo1bppByteArray.

// data that feed to the printer later
private lateinit var printData: ByteArray

// pass your html string
fun preparePrintData(html: String) {
    val bitmap = Html2Bitmap.Builder()
        .setContext(context)
        .setBitmapWidth(printerFixedWidth) // 384
        .setContent(WebViewContent.html(html))
        .build().bitmap

    printData = bitmapTo1bppByteArray(bitmap)
}

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Send printData

The app shall receive onPrintDataRequested after getControllerInstance() and connectController(). The app should pass the printData in byte array format to the printer by sendPrinterData.

override fun onPrintDataRequested() {
    printerController?.sendPrinterData(printData)
}

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Print status

The app shall receive onPrinterStatus and onPrinterCompleted for printer status.

override fun onPrinterStatus(p0: PrintStatus?) {
    when (p0) {
        PrintStatus.OVERHEAT -> {
            // printer overheat, please wait
        }
        PrintStatus.NO_PAPER_OR_COVER_OPENED -> {
            // no paper or the cover is opened, please re-fill the paper roll and close the cover properly
        }
        PrintStatus.PRINTER_LOWBATTERY -> {
            // battery is low, please charge the APOLLO
        }
        PrintStatus.SUCCESS -> {
            // print success
        }
        else -> {
        }
    }
}

override fun onPrinterCompleted() {
    // do something
}

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