Add DpadScroller to scroll a specific distance on each key event

dpadrecyclerview/src/main/java/com/rubensousa/dpadrecyclerview/DpadScroller.kt

@@ -0,0 +1,138 @@
+package com.rubensousa.dpadrecyclerview
+
+import android.view.KeyEvent
+import android.view.ViewGroup
+import androidx.recyclerview.widget.RecyclerView
+
+/**
+ * A helper class that allows scrolling a [DpadRecyclerView] based on specific scroll distances,
+ * ignoring the default alignment behavior.
+ *
+ * A typical use case for this class is a terms & conditions page,
+ * where a large amount of text is displayed, which the user isn't expected to interact with
+ */
+class DpadScroller(
+    private val calculator: ScrollDistanceCalculator = DefaultScrollDistanceCalculator(),
+) {
+
+    private var recyclerView: DpadRecyclerView? = null
+    private val keyListener = KeyListener()
+    private var smoothScrollEnabled = true
+
+    /**
+     * Attaches this [DpadScroller] to a new [DpadRecyclerView] to start observing key events.
+     * If you no longer need this behavior, call [detach]
+     *
+     * @param recyclerView The RecyclerView that will be scrolled discretely
+     */
+    fun attach(recyclerView: DpadRecyclerView) {
+        detach()
+        this.recyclerView = recyclerView
+        recyclerView.descendantFocusability = ViewGroup.FOCUS_BLOCK_DESCENDANTS
+        recyclerView.setOnKeyInterceptListener(keyListener)
+    }
+
+    /**
+     * Stops observing key events to scroll the current attached [DpadRecyclerView], if any exists
+     */
+    fun detach() {
+        recyclerView?.descendantFocusability = ViewGroup.FOCUS_AFTER_DESCENDANTS
+        recyclerView?.setOnKeyInterceptListener(null)
+        recyclerView = null
+    }
+
+    /**
+     * Enables or disables smooth scrolling on key events
+     */
+    fun setSmoothScrollEnabled(enabled: Boolean) {
+        smoothScrollEnabled = enabled
+    }
+
+    private inner class KeyListener : DpadRecyclerView.OnKeyInterceptListener {
+
+        override fun onInterceptKeyEvent(event: KeyEvent): Boolean {
+            val currentRecyclerView = recyclerView ?: return false
+            when (event.action) {
+                KeyEvent.ACTION_DOWN -> {
+                    return if (currentRecyclerView.getOrientation() == RecyclerView.VERTICAL) {
+                        scrollVertically(currentRecyclerView, event)
+                    } else {
+                        scrollHorizontally(currentRecyclerView, event)
+                    }
+                }
+            }
+            return false
+        }
+
+        private fun scrollVertically(recyclerView: DpadRecyclerView, event: KeyEvent): Boolean {
+            val scrollDistance = calculator.calculateScrollDistance(recyclerView, event)
+            when (event.keyCode) {
+                KeyEvent.KEYCODE_DPAD_DOWN -> {
+                    if (smoothScrollEnabled) {
+                        recyclerView.smoothScrollBy(0, scrollDistance)
+                    } else {
+                        recyclerView.scrollBy(0, scrollDistance)
+                    }
+                    return true
+                }
+
+                KeyEvent.KEYCODE_DPAD_UP -> {
+                    if (smoothScrollEnabled) {
+                        recyclerView.smoothScrollBy(0, -scrollDistance)
+                    } else {
+                        recyclerView.scrollBy(0, -scrollDistance)
+                    }
+                    return true
+                }
+            }
+            return false
+        }
+
+        private fun scrollHorizontally(recyclerView: DpadRecyclerView, event: KeyEvent): Boolean {
+            val scrollDistance = calculator.calculateScrollDistance(recyclerView, event)
+            when (event.keyCode) {
+                KeyEvent.KEYCODE_DPAD_RIGHT -> {
+                    if (smoothScrollEnabled) {
+                        recyclerView.smoothScrollBy(0, scrollDistance)
+                    } else {
+                        recyclerView.scrollBy(0, scrollDistance)
+                    }
+                    return true
+                }
+
+                KeyEvent.KEYCODE_DPAD_LEFT -> {
+                    if (smoothScrollEnabled) {
+                        recyclerView.smoothScrollBy(0, -scrollDistance)
+                    } else {
+                        recyclerView.scrollBy(0, -scrollDistance)
+                    }
+                    return true
+                }
+            }
+            return false
+        }
+
+    }
+
+
+    interface ScrollDistanceCalculator {
+        /**
+         * @return the number of pixels we should scroll for this [event]
+         */
+        fun calculateScrollDistance(recyclerView: DpadRecyclerView, event: KeyEvent): Int
+    }
+
+    private class DefaultScrollDistanceCalculator : ScrollDistanceCalculator {
+        override fun calculateScrollDistance(
+            recyclerView: DpadRecyclerView,
+            event: KeyEvent
+        ): Int {
+            return if (recyclerView.getOrientation() == RecyclerView.VERTICAL) {
+                recyclerView.height / 4
+            } else {
+                recyclerView.width / 4
+            }
+        }
+    }
+
+}

sample/src/main/java/com/rubensousa/dpadrecyclerview/sample/ui/screen/main/MainViewModel.kt

@@ -40,7 +40,7 @@ class MainViewModel : ViewModel() {
             buildNestedFeatureList(),
             buildGridFeatureList(),
             buildComposeFeatureList(),
-            buildFocusFeatureList(),
+            buildScrollingFeatureList(),
             buildAnimationsFeatureList(),
         )
     }
@@ -106,13 +106,17 @@ class MainViewModel : ViewModel() {
         )
     }
 
-    private fun buildFocusFeatureList(): FeatureList {
+    private fun buildScrollingFeatureList(): FeatureList {
         return FeatureList(
-            title = "Focus",
+            title = "Scrolling features",
             destinations = listOf(
+                ScreenDestination(
+                    direction = MainFragmentDirections.openTextScrolling(),
+                    title = "Long text scrolling"
+                ),
                 ScreenDestination(
                     direction = MainFragmentDirections.openHorizontalLeanback(),
-                    title = "Searching for unknown pivot"
+                    title = "Searching for next view"
                 )
             ),
         )

sample/src/main/java/com/rubensousa/dpadrecyclerview/sample/ui/screen/text/TextAdapter.kt

@@ -0,0 +1,50 @@
+package com.rubensousa.dpadrecyclerview.sample.ui.screen.text
+
+import android.view.LayoutInflater
+import android.view.ViewGroup
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
+import androidx.recyclerview.widget.RecyclerView
+import com.rubensousa.dpadrecyclerview.sample.databinding.AdapterItemTextBinding
+
+
+class TextAdapter : ListAdapter<String, TextAdapter.TextItemViewHolder>(DIFF_CALLBACK) {
+
+    companion object {
+        private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<String>() {
+            override fun areItemsTheSame(oldItem: String, newItem: String): Boolean {
+                return oldItem == newItem
+            }
+            override fun areContentsTheSame(oldItem: String, newItem: String): Boolean {
+                return oldItem == newItem
+            }
+        }
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TextItemViewHolder {
+        return TextItemViewHolder(
+            AdapterItemTextBinding.inflate(
+                LayoutInflater.from(parent.context),
+                parent,
+                false
+            )
+        )
+    }
+
+    override fun onBindViewHolder(holder: TextItemViewHolder, position: Int) {
+        holder.bind(getItem(position))
+    }
+
+    class TextItemViewHolder(
+        val binding: AdapterItemTextBinding
+    ) : RecyclerView.ViewHolder(binding.root) {
+
+        fun bind(text: String) {
+            binding.textView.text = text
+        }
+
+    }
+
+
+}
+

sample/src/main/java/com/rubensousa/dpadrecyclerview/sample/ui/screen/text/TextScrollingFragment.kt

@@ -0,0 +1,56 @@
+package com.rubensousa.dpadrecyclerview.sample.ui.screen.text
+
+import android.os.Bundle
+import android.view.KeyEvent
+import android.view.View
+import androidx.fragment.app.Fragment
+import androidx.navigation.fragment.findNavController
+import com.rubensousa.dpadrecyclerview.DpadRecyclerView
+import com.rubensousa.dpadrecyclerview.DpadScroller
+import com.rubensousa.dpadrecyclerview.sample.R
+import com.rubensousa.dpadrecyclerview.sample.databinding.ScreenTextScrollingBinding
+import com.rubensousa.dpadrecyclerview.sample.ui.viewBinding
+import com.rubensousa.dpadrecyclerview.spacing.DpadLinearSpacingDecoration
+
+class TextScrollingFragment : Fragment(R.layout.screen_text_scrolling) {
+
+    private val binding by viewBinding(ScreenTextScrollingBinding::bind)
+    private val scroller = DpadScroller(object : DpadScroller.ScrollDistanceCalculator {
+        override fun calculateScrollDistance(
+            recyclerView: DpadRecyclerView,
+            event: KeyEvent
+        ): Int {
+            return recyclerView.height / 5
+        }
+    })
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        val adapter = TextAdapter()
+        val text = view.resources.getString(R.string.placeholder_text)
+        val list = mutableListOf<String>()
+        repeat(50) {
+            list.add(text)
+        }
+        adapter.submitList(list)
+        binding.recyclerView.apply {
+            this.adapter = adapter
+            addItemDecoration(
+                DpadLinearSpacingDecoration.create(
+                    itemSpacing = resources.getDimensionPixelOffset(R.dimen.grid_item_spacing)
+                )
+            )
+        }
+        scroller.attach(binding.recyclerView)
+        binding.backButton.setOnClickListener {
+            findNavController().popBackStack()
+        }
+        binding.recyclerView.requestFocus()
+    }
+
+    override fun onDestroyView() {
+        super.onDestroyView()
+        scroller.detach()
+    }
+
+}

sample/src/main/res/color/list_text_background.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<selector xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <item android:color="#2B2B2B" android:state_focused="true" />
+    <item android:color="@color/transparent" />
+</selector>

sample/src/main/res/drawable/ic_back.xml

@@ -0,0 +1,5 @@
+<vector android:autoMirrored="true" android:height="24dp"
+    android:tint="#000000" android:viewportHeight="24"
+    android:viewportWidth="24" android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillColor="@android:color/white" android:pathData="M19,11H7.83l4.88,-4.88c0.39,-0.39 0.39,-1.03 0,-1.42 -0.39,-0.39 -1.02,-0.39 -1.41,0l-6.59,6.59c-0.39,0.39 -0.39,1.02 0,1.41l6.59,6.59c0.39,0.39 1.02,0.39 1.41,0 0.39,-0.39 0.39,-1.02 0,-1.41L7.83,13H19c0.55,0 1,-0.45 1,-1s-0.45,-1 -1,-1z"/>
+</vector>

sample/src/main/res/layout/adapter_item_text.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/textView"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:duplicateParentState="true"
+    android:paddingHorizontal="24dp"
+    android:textColor="@color/white" />