ViewImageFragment: finalize transition to BigImageViewer. Now it should correctly handle EXIF rotation, do not stuck at transition and pick preview image if it's in cache but full image isn't

app/src/main/java/com/keylesspalace/tusky/fragment/ViewImageFragment.kt

@@ -25,11 +25,15 @@ import android.os.Bundle
 import android.util.Log
 import android.view.*
 import android.widget.TextView
+import androidx.exifinterface.media.ExifInterface
 import com.bumptech.glide.Glide
 import com.bumptech.glide.load.DataSource
 import com.bumptech.glide.load.engine.GlideException
 import com.bumptech.glide.request.RequestListener
+import com.bumptech.glide.request.target.CustomTarget
 import com.bumptech.glide.request.target.Target
+import com.bumptech.glide.request.transition.Transition
+import com.github.piasy.biv.BigImageViewer
 import com.github.piasy.biv.loader.ImageLoader
 import com.github.piasy.biv.view.GlideImageViewFactory
 import com.keylesspalace.tusky.R
@@ -42,9 +46,10 @@ import kotlinx.android.synthetic.main.fragment_view_image.*
 import java.io.File
 import java.lang.Exception
 import kotlin.math.abs
+import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
 
 
-class ViewImageFragment : ViewMediaFragment(), ImageLoader.Callback, View.OnTouchListener {
+class ViewImageFragment : ViewMediaFragment() {
     interface PhotoActionsListener {
         fun onBringUp()
         fun onDismiss()
@@ -60,6 +65,10 @@ class ViewImageFragment : ViewMediaFragment(), ImageLoader.Callback, View.OnTouc
     @Volatile
     private var startedTransition = false
 
+    private var uri = Uri.EMPTY
+    private var previewUri = Uri.EMPTY
+    private var showingPreview = false
+
     override lateinit var descriptionView: TextView
     override fun onAttach(context: Context) {
         super.onAttach(context)
@@ -70,7 +79,11 @@ class ViewImageFragment : ViewMediaFragment(), ImageLoader.Callback, View.OnTouc
         descriptionView = mediaDescription
         photoView.transitionName = url
         startedTransition = false
-        loadImageFromNetwork(url, previewUrl)
+        uri = Uri.parse(url)
+        if(previewUrl != null && !previewUrl.equals(url)) {
+            previewUri = Uri.parse(previewUrl)
+        }
+        loadImageFromNetwork()
     }
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
@@ -78,9 +91,11 @@ class ViewImageFragment : ViewMediaFragment(), ImageLoader.Callback, View.OnTouc
         return inflater.inflate(R.layout.fragment_view_image, container, false)
     }
 
+    private lateinit var gestureDetector : GestureDetector
+
+    private val imageOnTouchListener = object : View.OnTouchListener {
         private var lastY = 0.0f
         private var swipeStartedWithOneFinger = false
-    private lateinit var gestureDetector : GestureDetector
 
         override fun onTouch(v: View, event: MotionEvent): Boolean {
             // This part is for scaling/translating on vertical move.
@@ -92,8 +107,6 @@ class ViewImageFragment : ViewMediaFragment(), ImageLoader.Callback, View.OnTouc
                 return false
             }
 
-        var result = false
-
             when(event.action) {
                 MotionEvent.ACTION_DOWN -> {
                     swipeStartedWithOneFinger = true
@@ -115,13 +128,14 @@ class ViewImageFragment : ViewMediaFragment(), ImageLoader.Callback, View.OnTouc
                             photoView.scaleX = scale
                             lastY = event.rawY
                         }
-                    result = true
                     }
                 }
             }
 
-        return result
+            return false
         }
+    }
+
 
     @SuppressLint("ClickableViewAccessibility")
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
@@ -135,7 +149,7 @@ class ViewImageFragment : ViewMediaFragment(), ImageLoader.Callback, View.OnTouc
         })
 
         // photoView.setOnTouchListener(this)
-        photoView.setImageLoaderCallback(this)
+        photoView.setImageLoaderCallback(imageLoaderCallback)
         photoView.setImageViewFactory(GlideImageViewFactory())
 
         val arguments = this.requireArguments()
@@ -190,33 +204,88 @@ class ViewImageFragment : ViewMediaFragment(), ImageLoader.Callback, View.OnTouc
         photoView.ssiv?.recycle()
     }
 
-    private fun loadImageFromNetwork(url: String, previewUrl: String?) {
-        photoView.showImage(Uri.parse(previewUrl), Uri.parse(url))
+    private inner class DummyCacheTarget(val ctx: Context, val requestPreview : Boolean) : CustomTarget<File>() {
+        override fun onLoadCleared(placeholder: Drawable?) {}
+        override fun onLoadFailed(errorDrawable: Drawable?) {
+            if(requestPreview) {
+                // no preview, no full image in cache, load full image
+                // forget about fancy transition
+                showingPreview = false
+                photoView.showImage(uri)
+            } else {
+                // let's start downloading full image that we supposedly don't have
+                BigImageViewer.prefetch(uri)
+
+                // meanwhile poke cache about preview image
+                Glide.with(ctx).asFile()
+                        .load(previewUri)
+                        .dontAnimate()
+                        .onlyRetrieveFromCache(true)
+                        .into(DummyCacheTarget(ctx, true))
+            }
         }
 
+        override fun onResourceReady(resource: File, transition: Transition<in File>?) {
+            showingPreview = requestPreview
+            if(requestPreview) {
+                // have preview cached but not full image
+                photoView.showImage(previewUri, uri, true)
+            } else {
+                photoView.showImage(uri)
+            }
+        }
+    }
+
+    private fun loadImageFromNetwork() {
+        Glide.with(this).asFile()
+            .load(uri)
+            .onlyRetrieveFromCache(true)
+            .dontAnimate()
+            .into(DummyCacheTarget(context!!, false))
+    }
+
+    override fun onTransitionEnd() {
+        // if we had preview, load full image, as transition has ended
+        if (showingPreview) {
+            showingPreview = false
+            photoView.loadMainImageNow()
+        }
+    }
+
+    private val imageLoaderCallback = object : ImageLoader.Callback {
         override fun onSuccess(image: File?) {
-        progressBar?.hide() // Always hide the progress bar on success
-        photoActionsListener.onBringUp()
-        photoView.ssiv?.setOnTouchListener(this)
+            if(!showingPreview) {
+                progressBar?.hide()
+                photoView.ssiv?.let {
+                    it.orientation = SubsamplingScaleImageView.ORIENTATION_USE_EXIF
+                    it.setOnTouchListener(imageOnTouchListener)
+                }
+            }
         }
 
         override fun onFail(error: Exception?) {
             progressBar?.hide()
-        photoActionsListener.onBringUp()
         }
 
         override fun onCacheHit(imageType: Int, image: File?) {
+            // image is here, bring up the activity!
+            photoActionsListener.onBringUp()
+        }
+
+        override fun onStart() {
+            // cache miss but image is downloading, bring up the activity
+            photoActionsListener.onBringUp()
         }
 
         override fun onCacheMiss(imageType: Int, image: File?) {
+            // this callback is useless because it's called after
+            // image is downloaded or pulled from cache
+            // so in case of cache miss, onStart is used
         }
 
-    override fun onFinish() {
-    }
-
+        override fun onFinish() {}
         override fun onProgress(progress: Int) {
-    }
-
-    override fun onTransitionEnd() {
+            // TODO: make use of it :)
+        }
     }
 }