Add checkerboard background to the images in the image view

A checkerboard is drawn beneath the image in the imageview to allow
a simpler viewing of images with transparency

androidApp/src/main/java/bou/amine/apps/readerforselfossv2/android/fragments/ImageFragment.kt

@@ -1,21 +1,23 @@
 package bou.amine.apps.readerforselfossv2.android.fragments
 
+import android.graphics.drawable.Drawable
+import android.graphics.drawable.LayerDrawable
 import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
+import bou.amine.apps.readerforselfossv2.android.R
 import bou.amine.apps.readerforselfossv2.android.databinding.FragmentImageBinding
 import com.bumptech.glide.Glide
-import com.bumptech.glide.load.engine.DiskCacheStrategy
+import com.bumptech.glide.request.target.ImageViewTarget
-import com.bumptech.glide.request.RequestOptions
 
 class ImageFragment : Fragment() {
 
     private lateinit var imageUrl : String
-    private val glideOptions = RequestOptions.diskCacheStrategyOf(DiskCacheStrategy.ALL)
     private var _binding: FragmentImageBinding? = null
     private val binding get() = _binding
+    private lateinit var layers: LayerDrawable
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -29,10 +31,18 @@ class ImageFragment : Fragment() {
 
         binding!!.photoView.visibility = View.VISIBLE
         Glide.with(activity)
-                .asBitmap()
-                .apply(glideOptions)
                 .load(imageUrl)
-                .into(binding!!.photoView)
+                .into(object : ImageViewTarget<Drawable>(binding!!.photoView) {
+                    override fun setResource(resource: Drawable?) {
+                        val background = resources.getDrawable(R.drawable.checkerboard, context?.theme)
+                        layers = LayerDrawable(arrayOf(background, resource))
+                        binding!!.photoView.setImageDrawable(layers)
+                    }
+
+                    override fun onLoadCleared(placeholder: Drawable?) {
+                        layers = LayerDrawable(emptyArray())
+                    }
+                })
 
         return view
     }

androidApp/src/main/res/drawable/checkerboard.xml

@@ -0,0 +1,5 @@
+<bitmap
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:dither="true"
+    android:src="@drawable/checktile"
+    android:tileMode="repeat"/>

androidApp/src/main/res/layout/fragment_image.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
@@ -9,8 +9,8 @@
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:layout_centerVertical="true"
-        android:layout_centerHorizontal="true"
+        android:adjustViewBounds="true"
-        android:background="@android:color/black"
+        android:background="?attr/colorOnBackground"
         app:srcCompat="@android:drawable/screen_background_dark" />
 
-</androidx.coordinatorlayout.widget.CoordinatorLayout>
+</RelativeLayout>