Improve image viewer (#1843)

This commit does 3 things:
1. Replaces PhotoView (which is abandonware) with modern TouchImageView
2. Fixes an issue with panning images. Gesture was not intercepted
properly and pager was taking control instead of image being moved.
3. Adds feedback to dismissing of images with vertical gesture.

app/build.gradle

@@ -178,7 +178,7 @@ dependencies {
 
     implementation "com.github.connyduck:sparkbutton:4.0.0"
 
-    implementation "com.github.chrisbanes:PhotoView:2.3.0"
+    implementation 'com.github.MikeOrtiz:TouchImageView:3.0.1'
 
     implementation "com.mikepenz:materialdrawer:$materialdrawerVersion"
     implementation "com.mikepenz:materialdrawer-iconics:$materialdrawerVersion"

app/src/main/java/com/keylesspalace/tusky/components/compose/dialog/CaptionDialog.kt

@@ -33,9 +33,9 @@ import at.connyduck.sparkbutton.helpers.Utils
 import com.bumptech.glide.Glide
 import com.bumptech.glide.request.target.CustomTarget
 import com.bumptech.glide.request.transition.Transition
-import com.github.chrisbanes.photoview.PhotoView
 import com.keylesspalace.tusky.R
 import com.keylesspalace.tusky.util.withLifecycleContext
+import com.ortiz.touchview.TouchImageView
 
 // https://github.com/tootsuite/mastodon/blob/1656663/app/models/media_attachment.rb#L94
 private const val MEDIA_DESCRIPTION_CHARACTER_LIMIT = 420
@@ -50,9 +50,8 @@ fun <T> T.makeCaptionDialog(existingDescription: String?,
     dialogLayout.setPadding(padding, padding, padding, padding)
 
     dialogLayout.orientation = LinearLayout.VERTICAL
-    val imageView = PhotoView(this).apply {
+    val imageView = TouchImageView(this).apply {
-        // If it seems a lot, try opening an image of A4 format or similar
+        maxZoom = 6f
-        maximumScale = 6.0f
     }
 
     val displayMetrics = DisplayMetrics()

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

@@ -21,9 +21,7 @@ import android.annotation.SuppressLint
 import android.content.Context
 import android.graphics.drawable.Drawable
 import android.os.Bundle
-import android.view.LayoutInflater
+import android.view.*
-import android.view.View
-import android.view.ViewGroup
 import android.widget.ImageView
 import android.widget.TextView
 import com.bumptech.glide.Glide
@@ -31,7 +29,6 @@ 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.Target
-import com.github.chrisbanes.photoview.PhotoViewAttacher
 import com.keylesspalace.tusky.R
 import com.keylesspalace.tusky.entity.Attachment
 import com.keylesspalace.tusky.util.hide
@@ -48,11 +45,11 @@ class ViewImageFragment : ViewMediaFragment() {
         fun onPhotoTap()
     }
 
-    private lateinit var attacher: PhotoViewAttacher
     private lateinit var photoActionsListener: PhotoActionsListener
     private lateinit var toolbar: View
     private var transition = BehaviorSubject.create<Unit>()
     private var shouldStartTransition = false
+
     // Volatile: Image requests happen on background thread and we want to see updates to it
     // immediately on another thread. Atomic is an overkill for such thing.
     @Volatile
@@ -67,23 +64,6 @@ class ViewImageFragment : ViewMediaFragment() {
     override fun setupMediaView(url: String, previewUrl: String?) {
         descriptionView = mediaDescription
         photoView.transitionName = url
-        attacher = PhotoViewAttacher(photoView).apply {
-            // Clicking outside the photo closes the viewer.
-            setOnOutsidePhotoTapListener { photoActionsListener.onDismiss() }
-            setOnClickListener { onMediaTap() }
-
-            /* A vertical swipe motion also closes the viewer. This is especially useful when the photo
-             * mostly fills the screen so clicking outside is difficult. */
-            setOnSingleFlingListener { _, _, velocityX, velocityY ->
-                var result = false
-                if (abs(velocityY) > abs(velocityX)) {
-                    photoActionsListener.onDismiss()
-                    result = true
-                }
-                result
-            }
-        }
-
         startedTransition = false
         loadImageFromNetwork(url, previewUrl, photoView)
     }
@@ -94,10 +74,66 @@ class ViewImageFragment : ViewMediaFragment() {
         return inflater.inflate(R.layout.fragment_view_image, container, false)
     }
 
+    @SuppressLint("ClickableViewAccessibility")
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 
-        val arguments = this.arguments!!
+        val gestureDetector = GestureDetector(requireContext(), object : GestureDetector.SimpleOnGestureListener() {
+            override fun onSingleTapConfirmed(e: MotionEvent?): Boolean {
+                onMediaTap()
+                return true
+            }
+        })
+
+        var lastY = 0f
+        photoView.setOnTouchListener { _, event ->
+            // This part is for scaling/translating on vertical move.
+            // We use raw coordinates to get the correct ones during scaling
+            var result = true
+
+            gestureDetector.onTouchEvent(event)
+
+            if (event.action == MotionEvent.ACTION_DOWN) {
+                lastY = event.rawY
+            } else if (!photoView.isZoomed && event.action == MotionEvent.ACTION_MOVE) {
+                val diff = event.rawY - lastY
+                // This code is to prevent transformations during page scrolling
+                // If we are already translating or we reached the threshold, then transform.
+                if (photoView.translationY != 0f || abs(diff) > 40) {
+                    photoView.translationY += (diff)
+                    val scale = (-abs(photoView.translationY) / 720 + 1).coerceAtLeast(0.5f)
+                    photoView.scaleY = scale
+                    photoView.scaleX = scale
+                    lastY = event.rawY
+                }
+                return@setOnTouchListener true
+            } else if (event.action == MotionEvent.ACTION_UP || event.action == MotionEvent.ACTION_CANCEL) {
+                onGestureEnd()
+            } else if (event.pointerCount >= 2 || photoView.canScrollHorizontally(1) && photoView.canScrollHorizontally(-1)) {
+                // Starting from here is adapted code from TouchImageView to play nice with pager.
+
+                // Can scroll horizontally checks if there's still a part of the image.
+                // That can be scrolled until you reach the edge multi-touch event.
+                val parent = view.parent
+                result = when (event.action) {
+                    MotionEvent.ACTION_DOWN, MotionEvent.ACTION_MOVE -> {
+                        // Disallow RecyclerView to intercept touch events.
+                        parent.requestDisallowInterceptTouchEvent(true)
+                        // Disable touch on view
+                        false
+                    }
+                    MotionEvent.ACTION_UP -> {
+                        // Allow RecyclerView to intercept touch events.
+                        parent.requestDisallowInterceptTouchEvent(false)
+                        true
+                    }
+                    else -> true
+                }
+            }
+            result
+        }
+
+        val arguments = this.requireArguments()
         val attachment = arguments.getParcelable<Attachment>(ARG_ATTACHMENT)
         this.shouldStartTransition = arguments.getBoolean(ARG_START_POSTPONED_TRANSITION)
         val url: String?
@@ -116,6 +152,14 @@ class ViewImageFragment : ViewMediaFragment() {
         finalizeViewSetup(url, attachment?.previewUrl, description)
     }
 
+    private fun onGestureEnd() {
+        if (abs(photoView.translationY) > 180) {
+            photoActionsListener.onDismiss()
+        } else {
+            photoView.animate().translationY(0f).scaleX(1f).scaleY(1f).start()
+        }
+    }
+
     private fun onMediaTap() {
         photoActionsListener.onPhotoTap()
     }
@@ -155,7 +199,6 @@ class ViewImageFragment : ViewMediaFragment() {
                                 .load(previewUrl)
                                 .dontAnimate()
                                 .onlyRetrieveFromCache(true)
-                                .centerInside()
                                 .addListener(ImageRequestListener(true, isThumnailRequest = true)))
                     else it
                 }
@@ -164,7 +207,6 @@ class ViewImageFragment : ViewMediaFragment() {
                         .centerInside()
                         .addListener(ImageRequestListener(false, isThumnailRequest = false))
                 )
-                .centerInside()
                 .addListener(ImageRequestListener(true, isThumnailRequest = false))
                 .into(photoView)
     }
@@ -225,13 +267,7 @@ class ViewImageFragment : ViewMediaFragment() {
                 // another branch. take() will unsubscribe after we have it to not leak menmory
                 transition
                         .take(1)
-                        .subscribe {
+                        .subscribe { target.onResourceReady(resource, null) }
-                            target.onResourceReady(resource, null)
-                            // It's needed. Don't ask why, I don't know, setImageDrawable() should
-                            // do it by itself but somehow it doesn't work automatically.
-                            // Just do it. If you don't, image will jump around when touched.
-                            attacher.update()
-                        }
             }
             return true
         }

app/src/main/res/layout/fragment_view_image.xml

@@ -4,11 +4,10 @@
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:layout_gravity="center"
     android:clickable="true"
     android:focusable="true">
 
-    <com.github.chrisbanes.photoview.PhotoView
+    <com.ortiz.touchview.TouchImageView
         android:id="@+id/photoView"
         android:layout_width="match_parent"
         android:layout_height="match_parent" />