[Deprecated - see the newer version] PDFPagerAdapter subclass that allows the user to zoom in and out with more image quality. Conversion to Kotlin was very quick and code is not optimal. Suitable for old versions of the library

SubsamplingPdfPagerAdapter.kt

import android.app.Activity
import android.content.Context
import android.graphics.Bitmap
import android.graphics.pdf.PdfRenderer
import android.support.v4.view.ViewPager
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import com.davemorrissey.labs.subscaleview.ImageSource
import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
import com.patrimonioglobalgra.audioguiasgranada.R
import es.voghdev.pdfviewpager.library.adapter.BasePDFPagerAdapter
import es.voghdev.pdfviewpager.library.adapter.BitmapContainer
import es.voghdev.pdfviewpager.library.adapter.PdfRendererParams
import es.voghdev.pdfviewpager.library.adapter.SimpleBitmapPool

/**
* Suitable for libraries PdfViewPager v1.0.3 and SubsamplingScaleImageView 3.10.0
* implementation 'com.davemorrissey.labs:subsampling-scale-image-view:3.10.0'
* implementation 'es.voghdev.pdfviewpager:library:1.0.3'
*/
class SubsamplingPdfPagerAdapter : BasePDFPagerAdapter {
    var inflater: LayoutInflater? = null
    var renderer: PdfRenderer? = null
    var bitmapContainer: BitmapContainer? = null
    var context: Context? = null

    constructor(context: Context?, pdfPath: String) : super(context, pdfPath, 1) {
        inflater = context?.getSystemService(Activity.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        renderer = PdfRenderer(getSeekableFileDescriptor(pdfPath))
        val params = extractPdfParams(renderer)
        bitmapContainer = SimpleBitmapPool(params)
        this.context = context
    }

    constructor(context: Context?, pdfPath: String, offScreenSize: Int) : super(context, pdfPath, offScreenSize) {
        inflater = context?.getSystemService(Activity.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        renderer = PdfRenderer(getSeekableFileDescriptor(pdfPath))
        val params = extractPdfParams(renderer)
        bitmapContainer = SimpleBitmapPool(params)
        this.context = context
    }

    fun extractPdfParams(renderer: PdfRenderer?): PdfRendererParams {
        val samplePage: PdfRenderer.Page = getPDFPage(renderer, FIRST_PAGE);
        val params = PdfRendererParams()
        params.renderQuality = renderQuality
        params.offScreenSize = offScreenSize
        params.width = (samplePage.width * renderQuality).toInt()
        params.height = (samplePage.height * renderQuality).toInt()

        samplePage.close()

        return params
    }

    override fun getCount(): Int = 1

    override fun instantiateItem(container: ViewGroup, position: Int): Any {
        val v = inflater?.inflate(R.layout.view_custom_pdf_page, container, false)
        val ssiv: SubsamplingScaleImageView? =
                v?.findViewById(R.id.subsamplingImageView) as SubsamplingScaleImageView?

        if (renderer == null || getCount() < position) {
            return v ?: View(context)
        }

        val page: PdfRenderer.Page = getPDFPage(renderer, position)

        val bitmap: Bitmap? = bitmapContainer?.get(position)
        page.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY)
        page.close()

        ssiv?.setImage(ImageSource.bitmap(bitmap!!))

        (container as ViewPager).addView(v, 0)

        return v ?: View(context)
    }
}