add Drag selection to directories

app/src/main/kotlin/com/simplemobiletools/gallery/activities/MainActivity.kt

@@ -124,6 +124,10 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
     override fun onStop() {
         super.onStop()
         config.temporarilyShowHidden = false
+    }
+
+    override fun onDestroy() {
+        super.onDestroy()
         DirectoryAdapter.cleanup()
     }
 
@@ -211,6 +215,10 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
         }
     }
 
+    override fun itemLongClicked(position: Int) {
+        directories_grid.setDragSelectActive(position)
+    }
+
     private fun handleZooming() {
         val layoutManager = directories_grid.layoutManager as GridLayoutManager
         layoutManager.spanCount = config.dirColumnCnt

app/src/main/kotlin/com/simplemobiletools/gallery/adapters/DirectoryAdapter.kt

@@ -321,6 +321,10 @@ class DirectoryAdapter(val activity: SimpleActivity, val dirs: MutableList<Direc
 
     override fun getItemCount() = dirs.size
 
+    fun selectItem(pos: Int) {
+        toggleItemSelection(true, pos)
+    }
+
     fun selectRange(from: Int, to: Int, min: Int, max: Int) {
         if (from == to) {
             (min..max).filter { it != from }

app/src/main/kotlin/com/simplemobiletools/gallery/views/MyScalableRecyclerView.kt

@@ -1,13 +1,38 @@
 package com.simplemobiletools.gallery.views
 
 import android.content.Context
+import android.os.Handler
 import android.support.v7.widget.RecyclerView
 import android.util.AttributeSet
 import android.view.MotionEvent
 import android.view.ScaleGestureDetector
+import com.simplemobiletools.gallery.R
+import com.simplemobiletools.gallery.adapters.DirectoryAdapter
 
+// drag selection is based on https://github.com/afollestad/drag-select-recyclerview
 class MyScalableRecyclerView : RecyclerView {
-    var mScaleDetector: ScaleGestureDetector
+    private val AUTO_SCROLL_DELAY = 25L
+
+    private var mScaleDetector: ScaleGestureDetector
+
+    private var dragSelectActive = false
+    private var lastDraggedIndex = -1
+    private var minReached = 0
+    private var maxReached = 0
+    private var initialSelection = 0
+
+    private var hotspotHeight = 0
+    private var hotspotOffsetTop = 0
+    private var hotspotOffsetBottom = 0
+
+    private var hotspotTopBoundStart = 0
+    private var hotspotTopBoundEnd = 0
+    private var hotspotBottomBoundStart = 0
+    private var hotspotBottomBoundEnd = 0
+    private var autoScrollVelocity = 0
+
+    private var inTopHotspot = false
+    private var inBottomHotspot = false
 
     companion object {
         var mListener: ZoomListener? = null
@@ -20,22 +45,138 @@ class MyScalableRecyclerView : RecyclerView {
     constructor(context: Context, attrs: AttributeSet) : super(context, attrs)
 
     init {
+        hotspotHeight = context.resources.getDimensionPixelSize(R.dimen.dragselect_hotspot_height)
         mScaleDetector = ScaleGestureDetector(context, GestureListener())
     }
 
-    override fun dispatchTouchEvent(ev: MotionEvent): Boolean {
-        super.dispatchTouchEvent(ev)
-        if (ev.action == MotionEvent.ACTION_UP) {
-            mCurrScaleFactor = 1.0f
-            mLastUp = System.currentTimeMillis()
+    override fun onMeasure(widthSpec: Int, heightSpec: Int) {
+        super.onMeasure(widthSpec, heightSpec)
+        if (hotspotHeight > -1) {
+            hotspotTopBoundStart = hotspotOffsetTop
+            hotspotTopBoundEnd = hotspotOffsetTop + hotspotHeight
+            hotspotBottomBoundStart = measuredHeight - hotspotHeight - hotspotOffsetBottom
+            hotspotBottomBoundEnd = measuredHeight - hotspotOffsetBottom
+        }
     }
 
+    private var autoScrollHandler = Handler()
+    private val autoScrollRunnable = object : Runnable {
+        override fun run() {
+            if (inTopHotspot) {
+                scrollBy(0, -autoScrollVelocity)
+                autoScrollHandler.postDelayed(this, AUTO_SCROLL_DELAY)
+            } else if (inBottomHotspot) {
+                scrollBy(0, autoScrollVelocity)
+                autoScrollHandler.postDelayed(this, AUTO_SCROLL_DELAY)
+            }
+        }
+    }
+
+    override fun dispatchTouchEvent(ev: MotionEvent): Boolean {
+        if (!dragSelectActive)
+            super.dispatchTouchEvent(ev)
+
+        when (ev.action) {
+            MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
+                dragSelectActive = false
+                mCurrScaleFactor = 1.0f
+                mLastUp = System.currentTimeMillis()
+                return true
+            }
+
+            MotionEvent.ACTION_MOVE -> {
+                if (dragSelectActive) {
+                    val itemPosition = getItemPosition(ev)
+                    if (hotspotHeight > -1) {
+                        if (ev.y in hotspotTopBoundStart..hotspotTopBoundEnd) {
+                            inBottomHotspot = false
+                            if (!inTopHotspot) {
+                                inTopHotspot = true
+                                autoScrollHandler.removeCallbacks(autoScrollRunnable)
+                                autoScrollHandler.postDelayed(autoScrollRunnable, AUTO_SCROLL_DELAY.toLong())
+                            }
+
+                            val simulatedFactor = (hotspotTopBoundEnd - hotspotTopBoundStart).toFloat()
+                            val simulatedY = ev.y - hotspotTopBoundStart
+                            autoScrollVelocity = (simulatedFactor - simulatedY).toInt() / 2
+                        } else if (ev.y in hotspotBottomBoundStart..hotspotBottomBoundEnd) {
+                            inTopHotspot = false
+                            if (!inBottomHotspot) {
+                                inBottomHotspot = true
+                                autoScrollHandler.removeCallbacks(autoScrollRunnable)
+                                autoScrollHandler.postDelayed(autoScrollRunnable, AUTO_SCROLL_DELAY.toLong())
+                            }
+
+                            val simulatedY = ev.y + hotspotBottomBoundEnd
+                            val simulatedFactor = (hotspotBottomBoundStart + hotspotBottomBoundEnd).toFloat()
+                            autoScrollVelocity = (simulatedY - simulatedFactor).toInt() / 2
+                        } else if (inTopHotspot || inBottomHotspot) {
+                            autoScrollHandler.removeCallbacks(autoScrollRunnable)
+                            inTopHotspot = false
+                            inBottomHotspot = false
+                        }
+                    }
+
+                    if (itemPosition != RecyclerView.NO_POSITION && lastDraggedIndex != itemPosition) {
+                        lastDraggedIndex = itemPosition
+                        if (minReached == -1) {
+                            minReached = lastDraggedIndex
+                        }
+
+                        if (maxReached == -1) {
+                            maxReached = lastDraggedIndex
+                        }
+
+                        if (lastDraggedIndex > maxReached) {
+                            maxReached = lastDraggedIndex
+                        }
+
+                        if (lastDraggedIndex < minReached) {
+                            minReached = lastDraggedIndex
+                        }
+
+                        (adapter as DirectoryAdapter).selectRange(initialSelection, lastDraggedIndex, minReached, maxReached)
+
+                        if (initialSelection == lastDraggedIndex) {
+                            minReached = lastDraggedIndex
+                            maxReached = lastDraggedIndex
+                        }
+                    }
+
+                    return true
+                }
+            }
+        }
         return mScaleDetector.onTouchEvent(ev)
     }
 
+    fun setDragSelectActive(initialSelection: Int) {
+        if (dragSelectActive)
+            return
+
+        lastDraggedIndex = -1
+        minReached = -1
+        maxReached = -1
+        this.initialSelection = initialSelection
+        dragSelectActive = true
+        (adapter as DirectoryAdapter).selectItem(initialSelection)
+    }
+
+    private fun getItemPosition(e: MotionEvent): Int {
+        val v = findChildViewUnder(e.x, e.y) ?: return RecyclerView.NO_POSITION
+
+        if (v.tag == null || v.tag !is RecyclerView.ViewHolder) {
+            throw IllegalStateException("Make sure your adapter makes a call to super.onBindViewHolder(), and doesn't override itemView tags.")
+        }
+
+        val holder = v.tag as RecyclerView.ViewHolder
+        return holder.adapterPosition
+    }
+
+
     class GestureListener : ScaleGestureDetector.SimpleOnScaleGestureListener() {
-        val ZOOM_IN_THRESHOLD = -0.6f
-        val ZOOM_OUT_THRESHOLD = 0.25f
+        private val ZOOM_IN_THRESHOLD = -0.4f
+        private val ZOOM_OUT_THRESHOLD = 0.15f
 
         override fun onScale(detector: ScaleGestureDetector): Boolean {
             if (System.currentTimeMillis() - mLastUp < 1000)

app/src/main/res/values/dimens.xml

@@ -7,4 +7,6 @@
     <dimen name="play_outline_size_big">150dp</dimen>
     <dimen name="timer_padding">24dp</dimen>
     <dimen name="tmb_shadow_height">50dp</dimen>
+
+    <dimen name="dragselect_hotspot_height">56dp</dimen>
 </resources>