Allow apps to provide customized ViewHolders

imageviewer/src/main/java/com/stfalcon/imageviewer/StfalconImageViewer.java

@@ -25,6 +25,7 @@
 import com.stfalcon.imageviewer.listeners.OnDismissListener;
 import com.stfalcon.imageviewer.listeners.OnImageChangeListener;
 import com.stfalcon.imageviewer.loader.ImageLoader;
+import com.stfalcon.imageviewer.viewer.viewholder.ViewHolderLoader;
 import com.stfalcon.imageviewer.viewer.builder.BuilderData;
 import com.stfalcon.imageviewer.viewer.dialog.ImageViewerDialog;
 
@@ -127,11 +128,22 @@ public Builder(Context context, T[] images, ImageLoader<T> imageLoader) {
             this(context, new ArrayList<>(Arrays.asList(images)), imageLoader);
         }
 
+        public Builder(Context context, T[] images, ImageLoader<T> imageLoader,
+                       ViewHolderLoader<T> viewHolderLoader) {
+            this(context, new ArrayList<>(Arrays.asList(images)), imageLoader, viewHolderLoader);
+        }
+
         public Builder(Context context, List<T> images, ImageLoader<T> imageLoader) {
             this.context = context;
             this.data = new BuilderData<>(images, imageLoader);
         }
 
+        public Builder(Context context, List<T> images, ImageLoader<T> imageLoader,
+                       ViewHolderLoader<T> viewHolderLoader) {
+            this.context = context;
+            this.data = new BuilderData<>(images, imageLoader, viewHolderLoader);
+        }
+
         /**
          * Sets a position to start viewer from.
          *

imageviewer/src/main/java/com/stfalcon/imageviewer/common/pager/RecyclingPagerAdapter.kt

@@ -8,7 +8,7 @@ import android.view.ViewGroup
 import androidx.viewpager.widget.PagerAdapter
 import com.stfalcon.imageviewer.common.extensions.forEach
 
-internal abstract class RecyclingPagerAdapter<VH : RecyclingPagerAdapter.ViewHolder>
+abstract class RecyclingPagerAdapter<VH : RecyclingPagerAdapter.ViewHolder>
     : PagerAdapter() {
 
     companion object {
@@ -107,7 +107,7 @@ internal abstract class RecyclingPagerAdapter<VH : RecyclingPagerAdapter.ViewHol
         }
     }
 
-    internal abstract class ViewHolder(internal val itemView: View) {
+    abstract class ViewHolder(val itemView: View) {
 
         companion object {
             private val STATE = ViewHolder::class.java.simpleName

imageviewer/src/main/java/com/stfalcon/imageviewer/viewer/adapter/ImagesPagerAdapter.kt

@@ -20,33 +20,42 @@ import android.content.Context
 import android.view.View
 import android.view.ViewGroup
 import com.github.chrisbanes.photoview.PhotoView
-import com.stfalcon.imageviewer.common.extensions.resetScale
 import com.stfalcon.imageviewer.common.pager.RecyclingPagerAdapter
 import com.stfalcon.imageviewer.loader.ImageLoader
+import com.stfalcon.imageviewer.viewer.viewholder.ViewHolderLoader
+import com.stfalcon.imageviewer.viewer.viewholder.DefaultViewHolder
 
 internal class ImagesPagerAdapter<T>(
     private val context: Context,
     _images: List<T>,
     private val imageLoader: ImageLoader<T>,
-    private val isZoomingAllowed: Boolean
-) : RecyclingPagerAdapter<ImagesPagerAdapter<T>.ViewHolder>() {
-
+    private val isZoomingAllowed: Boolean,
+    private val viewHolderLoader: ViewHolderLoader<T>
+) : RecyclingPagerAdapter<DefaultViewHolder<T>>() {
     private var images = _images
-    private val holders = mutableListOf<ViewHolder>()
+    private val holders = mutableListOf<DefaultViewHolder<T>>()
+    private var primaryPos = -1
+
+    companion object {
+        val photoViewId = View.generateViewId()
+    }
 
     fun isScaled(position: Int): Boolean =
-        holders.firstOrNull { it.position == position }?.isScaled ?: false
+        holders.firstOrNull { it.position == position }?.isScaled() ?: false
 
-    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DefaultViewHolder<T> {
         val photoView = PhotoView(context).apply {
+            id = photoViewId
             isEnabled = isZoomingAllowed
             setOnViewDragListener { _, _ -> setAllowParentInterceptOnEdge(scale == 1.0f) }
         }
 
-        return ViewHolder(photoView).also { holders.add(it) }
+        return viewHolderLoader.loadViewHolder(photoView).also {
+            it.imageLoader = imageLoader
+            holders.add(it) }
     }
 
-    override fun onBindViewHolder(holder: ViewHolder, position: Int) = holder.bind(position)
+    override fun onBindViewHolder(holder: DefaultViewHolder<T>, position: Int) = holder.bind(position, images[position])
 
     override fun getItemCount() = images.size
 
@@ -58,19 +67,15 @@ internal class ImagesPagerAdapter<T>(
     internal fun resetScale(position: Int) =
         holders.firstOrNull { it.position == position }?.resetScale()
 
-    internal inner class ViewHolder(itemView: View)
-        : RecyclingPagerAdapter.ViewHolder(itemView) {
+    fun onDialogClosed() = holders.forEach { it.onDialogClosed() }
 
-        internal var isScaled: Boolean = false
-            get() = photoView.scale > 1f
+    override fun setPrimaryItem(container: ViewGroup, position: Int, `object`: Any) {
+        super.setPrimaryItem(container, position, `object`)
 
-        private val photoView: PhotoView = itemView as PhotoView
-
-        fun bind(position: Int) {
-            this.position = position
-            imageLoader.loadImage(photoView, images[position])
+        // Only fire when the primary item has actually changed
+        if (position != primaryPos) {
+            primaryPos = position
+            holders.forEach { it.setIsVisible(it.position == primaryPos) }
         }
-
-        fun resetScale() = photoView.resetScale(animate = true)
     }
 }

imageviewer/src/main/java/com/stfalcon/imageviewer/viewer/builder/BuilderData.kt

@@ -21,7 +21,9 @@ import android.view.View
 import android.widget.ImageView
 import com.stfalcon.imageviewer.listeners.OnDismissListener
 import com.stfalcon.imageviewer.listeners.OnImageChangeListener
+import com.stfalcon.imageviewer.viewer.viewholder.DefaultViewHolderLoader
 import com.stfalcon.imageviewer.loader.ImageLoader
+import com.stfalcon.imageviewer.viewer.viewholder.ViewHolderLoader
 
 internal class BuilderData<T>(
     val images: List<T>,
@@ -38,4 +40,10 @@ internal class BuilderData<T>(
     var isZoomingAllowed = true
     var isSwipeToDismissAllowed = true
     var transitionView: ImageView? = null
+    var viewHolderLoader: ViewHolderLoader<T>? = DefaultViewHolderLoader()
+
+    constructor(images: List<T>, imageLoader: ImageLoader<T>, viewHolderLoader: ViewHolderLoader<T>)
+            : this(images, imageLoader) {
+        this.viewHolderLoader = viewHolderLoader
+    }
 }

imageviewer/src/main/java/com/stfalcon/imageviewer/viewer/dialog/ImageViewerDialog.kt

@@ -106,7 +106,10 @@ internal class ImageViewerDialog<T>(
             overlayView = builderData.overlayView
 
             setBackgroundColor(builderData.backgroundColor)
-            setImages(builderData.images, builderData.startPosition, builderData.imageLoader)
+
+
+            setImages(builderData.images, builderData.startPosition, builderData.imageLoader,
+                    builderData.viewHolderLoader)
 
             onPageChange = { position -> builderData.imageChangeListener?.onImageChange(position) }
             onDismiss = { dialog.dismiss() }

imageviewer/src/main/java/com/stfalcon/imageviewer/viewer/view/ImageViewerView.kt

@@ -46,7 +46,9 @@ import com.stfalcon.imageviewer.common.gestures.direction.SwipeDirection.UP
 import com.stfalcon.imageviewer.common.gestures.direction.SwipeDirectionDetector
 import com.stfalcon.imageviewer.common.gestures.dismiss.SwipeToDismissHandler
 import com.stfalcon.imageviewer.common.pager.MultiTouchViewPager
+import com.stfalcon.imageviewer.viewer.viewholder.DefaultViewHolderLoader
 import com.stfalcon.imageviewer.loader.ImageLoader
+import com.stfalcon.imageviewer.viewer.viewholder.ViewHolderLoader
 import com.stfalcon.imageviewer.viewer.adapter.ImagesPagerAdapter
 
 internal class ImageViewerView<T> @JvmOverloads constructor(
@@ -177,10 +179,12 @@ internal class ImageViewerView<T> @JvmOverloads constructor(
         findViewById<View>(R.id.backgroundView).setBackgroundColor(color)
     }
 
-    internal fun setImages(images: List<T>, startPosition: Int, imageLoader: ImageLoader<T>) {
+    internal fun setImages(images: List<T>, startPosition: Int, imageLoader: ImageLoader<T>,
+                           viewHolderLoader: ViewHolderLoader<T>?) {
         this.images = images
         this.imageLoader = imageLoader
-        this.imagesAdapter = ImagesPagerAdapter(context, images, imageLoader, isZoomingAllowed)
+        this.imagesAdapter = ImagesPagerAdapter(context, images, imageLoader, isZoomingAllowed,
+                viewHolderLoader ?: DefaultViewHolderLoader())
         this.imagesPager.adapter = imagesAdapter
         this.startPosition = startPosition
     }
@@ -253,6 +257,7 @@ internal class ImageViewerView<T> @JvmOverloads constructor(
     private fun prepareViewsForTransition() {
         transitionImageContainer.makeVisible()
         imagesPager.makeGone()
+        (imagesPager.adapter as? ImagesPagerAdapter<T>)?.onDialogClosed()
     }
 
     private fun prepareViewsForViewer() {

imageviewer/src/main/java/com/stfalcon/imageviewer/viewer/viewholder/DefaultViewHolder.kt

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2018 stfalcon.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.stfalcon.imageviewer.viewer.viewholder
+
+import android.view.View
+import com.github.chrisbanes.photoview.PhotoView
+import com.stfalcon.imageviewer.common.extensions.resetScale
+import com.stfalcon.imageviewer.common.pager.RecyclingPagerAdapter
+import com.stfalcon.imageviewer.loader.ImageLoader
+import com.stfalcon.imageviewer.viewer.adapter.ImagesPagerAdapter
+
+
+/**
+ * Subclasses may customize how the image pages are presented to the user.
+ * By overriding the constructor, subclasses may add additional views. The constructor is passed
+ * a zoomable PhotoView which is configured to behave well. Subclasses may customize this View,
+ * incorporate it into a more complex hierarchy, or ignore it altogether. The final View or
+ * ViewGroup must be passed to the super() constructor.
+ * By overriding the bind() method, subclasses may customize how images are loaded into views.
+ */
+open class DefaultViewHolder<T>(itemView: View)
+    : RecyclingPagerAdapter.ViewHolder(itemView) {
+
+    internal var imageLoader: ImageLoader<T>? = null
+
+    // If a subclass has incorporated the PhotoView into a ViewGroup, find it
+    // to ensure correct behavior by default
+    private var photoView: PhotoView? =
+            if (itemView is PhotoView) itemView
+            else itemView.findViewById(ImagesPagerAdapter.photoViewId)
+
+    // Subclasses should return True when they wish to handle Back button presses
+    // (e.g. when the image is zoomed in and should be un-zoomed when Back is pressed)
+    open fun isScaled() : Boolean = (photoView?.scale ?: 1f) > 1f
+
+    // Subclasses can respond to Back button presses here when isScaled() returns True
+    open fun resetScale() = photoView?.resetScale(animate = true)
+
+    open fun bind(position: Int, image: T) {
+        this.position = position
+        imageLoader?.loadImage(photoView, image)
+    }
+
+    // Subclasses may respond when the dialog window is closed (e.g. to stop video playback)
+    open fun onDialogClosed() {}
+
+    // Subclasses may respond when this ViewHolder's View moves on or off the screen
+    open fun setIsVisible(isVisible: Boolean) {}
+}

imageviewer/src/main/java/com/stfalcon/imageviewer/viewer/viewholder/DefaultViewHolderLoader.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2018 stfalcon.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.stfalcon.imageviewer.viewer.viewholder
+
+import com.github.chrisbanes.photoview.PhotoView
+
+
+class DefaultViewHolderLoader<T> : ViewHolderLoader<T> {
+    override fun loadViewHolder(photoView: PhotoView) = DefaultViewHolder<T>(photoView)
+}

imageviewer/src/main/java/com/stfalcon/imageviewer/viewer/viewholder/ViewHolderLoader.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2018 stfalcon.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.stfalcon.imageviewer.viewer.viewholder;
+
+import com.github.chrisbanes.photoview.PhotoView;
+
+/**
+ * Interface definition for a callback to be invoked when a ViewHolder must be created.
+ *
+ * Applications can use their own subclasses of DefaultViewHolder by passing a ViewHolderLoader
+ * implementation to StfalconImageViewer.Builder that returns their DefaultViewHolder subclass.
+ *
+ * N.B.! This class is written in Java for convenient use of lambdas due to languages compatibility issues.
+ */
+public interface ViewHolderLoader<T> {
+
+    /**
+     * Fires every time a new ViewHolder should be created
+     *
+     * @param photoView a {@link PhotoView} object, configured to behave well
+     */
+    DefaultViewHolder<T> loadViewHolder(PhotoView photoView);
+}