Add item left and right swipe background

app/src/main/java/com/readrops/app/activities/MainActivity.java

@@ -322,10 +322,12 @@ public class MainActivity extends AppCompatActivity implements SwipeRefreshLayou
 
         recyclerView.setAdapter(adapter);
 
-        new ItemTouchHelper(new ReadropsItemTouchCallback(
+        new ItemTouchHelper(new ReadropsItemTouchCallback(this,
                 new ReadropsItemTouchCallback.Config.Builder()
                         .swipeDirs(ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT)
                         .swipeCallback(this)
+                        .leftDraw(Color.DKGRAY, R.drawable.ic_read_later)
+                        .rightDraw(Color.DKGRAY, R.drawable.ic_read)
                         .build()))
                 .attachToRecyclerView(recyclerView);
 

app/src/main/java/com/readrops/app/utils/ReadropsItemTouchCallback.kt

@@ -1,9 +1,20 @@
 package com.readrops.app.utils
 
+import android.content.Context
+import android.graphics.Canvas
+import android.graphics.drawable.ColorDrawable
+import android.graphics.drawable.Drawable
+import android.view.View
+import androidx.annotation.ColorInt
+import androidx.annotation.DrawableRes
+import androidx.core.content.ContextCompat
 import androidx.recyclerview.widget.ItemTouchHelper
 import androidx.recyclerview.widget.RecyclerView
+import kotlin.math.abs
 
-class ReadropsItemTouchCallback(private val config: Config) : ItemTouchHelper.SimpleCallback(config.dragDirs, config.swipeDirs) {
+class ReadropsItemTouchCallback(private val context: Context, private val config: Config) : ItemTouchHelper.SimpleCallback(config.dragDirs, config.swipeDirs) {
+
+    private val iconHorizontalMargin = 40
 
     override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
         config.moveCallback?.onMove()
@@ -14,6 +25,53 @@ class ReadropsItemTouchCallback(private val config: Config) : ItemTouchHelper.Si
         config.swipeCallback?.onSwipe(viewHolder, direction)
     }
 
+    override fun onChildDraw(c: Canvas, recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, dX: Float, dY: Float, actionState: Int, isCurrentlyActive: Boolean) {
+        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
+
+        val background: ColorDrawable
+        var icon: Drawable? = null
+        val itemView: View = viewHolder.itemView
+        var draw = true // variable used to draw under some conditions
+
+        // do not draw anymore if the view has reached the screen's left/right side
+        if (abs(dX).toInt() == itemView.right) {
+            draw = false
+        } else if (abs(dX).toInt() == 0) {
+            draw = true
+        }
+
+        // left swipe
+        if (dX > 0 && config.leftDraw != null && draw) {
+            background = ColorDrawable(config.leftDraw.bgColor)
+            background.setBounds(itemView.left, itemView.top, dX.toInt(), itemView.bottom)
+
+            icon = ContextCompat.getDrawable(context, config.leftDraw.icon)!!
+            val iconMargin = (itemView.height - icon.intrinsicHeight) / 2
+            icon.setBounds(itemView.left + iconHorizontalMargin, itemView.top + iconMargin,
+                    itemView.left + iconHorizontalMargin + icon.intrinsicWidth, itemView.bottom - iconMargin)
+            // right swipe
+        } else if (dX < 0 && config.rightDraw != null && draw) {
+            background = ColorDrawable(config.rightDraw.bgColor)
+            background.setBounds(itemView.right + dX.toInt(), itemView.top, itemView.right, itemView.bottom)
+
+            icon = ContextCompat.getDrawable(context, config.rightDraw.icon)!!
+            val iconMargin = (itemView.height - icon.intrinsicHeight) / 2
+            icon.setBounds(itemView.right - iconHorizontalMargin - icon.intrinsicWidth, itemView.top + iconMargin,
+                    itemView.right - iconHorizontalMargin, itemView.bottom - iconMargin)
+        } else {
+            background = ColorDrawable()
+        }
+
+        background.draw(c)
+
+        if (dX > 0)
+            c.clipRect(itemView.left, itemView.top, dX.toInt(), itemView.bottom)
+        else if (dX < 0)
+            c.clipRect(itemView.right + dX.toInt(), itemView.top, itemView.right, itemView.bottom)
+
+        icon?.draw(c)
+    }
+
     override fun isItemViewSwipeEnabled(): Boolean {
         return config.swipeCallback != null
     }
@@ -30,10 +88,13 @@ class ReadropsItemTouchCallback(private val config: Config) : ItemTouchHelper.Si
         fun onSwipe(viewHolder: RecyclerView.ViewHolder, direction: Int)
     }
 
-    class Config(val dragDirs: Int = 0, val swipeDirs: Int = 0, val moveCallback: MoveCallback? = null,
+    class SwipeDraw(@ColorInt val bgColor: Int, @DrawableRes val icon: Int)
-                 val swipeCallback: SwipeCallback? = null) {
 
-        private constructor(builder: Builder) : this(builder.dragDirs, builder.swipeDirs, builder.moveCallback, builder.swipeCallback)
+    class Config(val dragDirs: Int = 0, val swipeDirs: Int = 0, val moveCallback: MoveCallback? = null,
+                 val swipeCallback: SwipeCallback? = null, val leftDraw: SwipeDraw? = null, val rightDraw: SwipeDraw? = null) {
+
+        private constructor(builder: Builder) : this(builder.dragDirs, builder.swipeDirs,
+                builder.moveCallback, builder.swipeCallback, builder.leftDraw, builder.rightDraw)
 
         class Builder {
             var dragDirs: Int = 0
@@ -48,6 +109,12 @@ class ReadropsItemTouchCallback(private val config: Config) : ItemTouchHelper.Si
             var swipeCallback: SwipeCallback? = null
                 private set
 
+            var leftDraw: SwipeDraw? = null
+                private set
+
+            var rightDraw: SwipeDraw? = null
+                private set
+
             fun dragDirs(dragDirs: Int) = apply { this.dragDirs = dragDirs }
 
             fun swipeDirs(swipeDirs: Int) = apply { this.swipeDirs = swipeDirs }
@@ -56,6 +123,10 @@ class ReadropsItemTouchCallback(private val config: Config) : ItemTouchHelper.Si
 
             fun swipeCallback(swipeCallback: SwipeCallback) = apply { this.swipeCallback = swipeCallback }
 
+            fun leftDraw(@ColorInt bgColor: Int, @DrawableRes icon: Int) = apply { this.leftDraw = SwipeDraw(bgColor, icon) }
+
+            fun rightDraw(@ColorInt bgColor: Int, @DrawableRes icon: Int) = apply { this.rightDraw = SwipeDraw(bgColor, icon) }
+
             fun build(): Config {
                 return Config(this)
             }