Show/hide presented pages by tapping thumbnails

README.md

@@ -6,6 +6,9 @@ Minimum Viable Goals:
 - [x] Autocrop margins
 - [ ] Open files the Android way - currently just a bundled test file
 - [ ] Delete+Reorder Pages - doesn't have to save the source file, but does need to save a change journal
+- - [x] Tap thumbnails to hide/show pages
+- - [ ] Drag thumbnails to rearrange pages
+- - [ ] Save metadata of these actions between sessions
 - [ ] Text Annotations - as above
 
 Stretch Goals:
@@ -14,4 +17,5 @@ Stretch Goals:
 - - [ ] synchronize views for different readers
 - - [ ] coordinate views for one reader multiscreen
 - [ ] Pen Annotations
+- [ ] Autocrop undesired elements (e.g. logo in top right corner, copyright footer)
 - [ ] Improve overall UI

app/src/main/java/com/lhw/pdf/MainActivity.kt

@@ -2,6 +2,7 @@ package com.lhw.pdf
 
 import android.app.Presentation
 import android.content.Context
+import android.graphics.PorterDuff
 import android.media.MediaRouter
 import android.os.Bundle
 import android.util.DisplayMetrics
@@ -40,6 +41,7 @@ class MainActivity : AppCompatActivity() {
     private lateinit var pdfDocument: PdfDocument
     private lateinit var presentationScroll: HorizontalScrollView
     private lateinit var presentationLayout: LinearLayout
+    private val showPages = mutableListOf<Boolean>()
 
     private fun inputStreamToCache(outputFilename: String, inputStream: InputStream): File {
         val fileCached = File(cacheDir, outputFilename)
@@ -61,12 +63,15 @@ class MainActivity : AppCompatActivity() {
 
     }
 
-    private fun updatePresentationImages() {
-        val maxHeight: Int = presentationDisplayMetrics.heightPixels
-        val maxWidth: Int = min(maxHeight*5/7, (presentationDisplayMetrics.widthPixels/pagesPerLandscape).toInt())
-        pdfDocument.renderPagesPresentation(maxWidth, maxHeight, renderAutoCrop)
+    private fun updatePresentationImages(rerender: Boolean = true) {
+        if (rerender) {
+            val maxHeight: Int = presentationDisplayMetrics.heightPixels
+            val maxWidth: Int = min(maxHeight*5/7, (presentationDisplayMetrics.widthPixels/pagesPerLandscape).toInt())
+            pdfDocument.renderPagesPresentation(maxWidth, maxHeight, renderAutoCrop)
+        }
         presentationLayout.removeAllViewsInLayout()
-        for (bitmap in pdfDocument.bitmapPagesPresentation.values) {
+        showPages.withIndex().filter { (i, show) -> (show) }.forEach { (i, show) ->
+            val bitmap = pdfDocument.bitmapPagesPresentation[i]
             val img = ImageView(this)
             img.setImageBitmap(bitmap)
             presentationLayout.addView(img)
@@ -110,10 +115,16 @@ class MainActivity : AppCompatActivity() {
         initializePdfDocument()
         pdfDocument.renderThumbnails(thumbnailWidth, thumbnailHeight)
         val container = binding.appBarMain.contentMain.thumbnailsLayout
-        for (bitmap in pdfDocument.bitmapThumbnails.values) {
+        for ((index, bitmap) in pdfDocument.bitmapThumbnails) {
             val img = ImageView(this)
             img.setImageBitmap(bitmap)
+            img.setOnClickListener {
+                showPages[index] = !showPages[index]
+                img.setColorFilter(if (showPages[index]) 0 else 0x7F000000, PorterDuff.Mode.DARKEN)
+                updatePresentationImages(false)
+            }
             container.addView(img)
+            showPages.add(true)
         }
         presentationView()