RecyclerView ItemTouchHelper Buttons on Swipe

Question

I am trying to port some iOS functionality to Android.

I intent to create a table where on swipe to the left shows 2 button: Edit and Delete.

I have been playing with it and I know I am very close. The secret really lies on the method OnChildDraw.

I would like to Draw a Rect that fits the text Delete then draw the Edit text besides it with their respective background color. The remaining white space when clicked should restore the row to its initial position.

I have managed to paint the background while the user is swiping to the sides but I don't know how to add the listeners and once it is swiped to the side, the dragging function begins to misbehave.

I am working on Xamarin but pure java solutions also are accepted as I can easily port them to c#.

    public class SavedPlacesItemTouchHelper : ItemTouchHelper.SimpleCallback
    {
        private SavedPlacesRecyclerviewAdapter adapter;
        private Paint paint = new Paint();
        private Context context;

        public SavedPlacesItemTouchHelper(Context context, SavedPlacesRecyclerviewAdapter adapter) : base(ItemTouchHelper.ActionStateIdle, ItemTouchHelper.Left)
        {
            this.context = context;
            this.adapter = adapter;
        }

        public override bool OnMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target)
        {
            return false;
        }

        public override void OnSwiped(RecyclerView.ViewHolder viewHolder, int direction)
        {
        }

        public override void OnChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, bool isCurrentlyActive)
        {
            float translationX = dX;
            View itemView = viewHolder.ItemView;
            float height = (float)itemView.Bottom - (float)itemView.Top;

            if (actionState == ItemTouchHelper.ActionStateSwipe && dX <= 0) // Swiping Left
            {
                 translationX = -Math.Min(-dX, height * 2);
                paint.Color = Color.Red;
                RectF background = new RectF((float)itemView.Right + translationX, (float)itemView.Top, (float)itemView.Right, (float)itemView.Bottom);
                c.DrawRect(background, paint);

                //viewHolder.ItemView.TranslationX = translationX;
            }
            else if (actionState == ItemTouchHelper.ActionStateSwipe && dX > 0) // Swiping Right
            {
                translationX = Math.Min(dX, height * 2);
                paint.Color = Color.Red;
                RectF background = new RectF((float)itemView.Right + translationX, (float)itemView.Top, (float)itemView.Right, (float)itemView.Bottom);
                c.DrawRect(background, paint);
            }

            base.OnChildDraw(c, recyclerView, viewHolder, translationX, dY, actionState, isCurrentlyActive);
        }
    }
}

This is what I currently have.

If you know how to add listeners or any suggestions please leave a comment!

UPDATE:

I just realized that on double tap on the white remaining space of the row already restore the row to its initial state. Not a single tap though :(

Answer 1

I struggled with the same issue, and tried to find a solution online. Most of the solutions use a two-layer approach (one layer view item, another layer buttons), but I want to stick with ItemTouchHelper only. At the end, I came up with a worked solution. Please check below.

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.Rect;
import android.graphics.RectF;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.helper.ItemTouchHelper;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;

public abstract class SwipeHelper extends ItemTouchHelper.SimpleCallback {

    public static final int BUTTON_WIDTH = YOUR_WIDTH_IN_PIXEL_PER_BUTTON
    private RecyclerView recyclerView;
    private List<UnderlayButton> buttons;
    private GestureDetector gestureDetector;
    private int swipedPos = -1;
    private float swipeThreshold = 0.5f;
    private Map<Integer, List<UnderlayButton>> buttonsBuffer;
    private Queue<Integer> recoverQueue;

    private GestureDetector.SimpleOnGestureListener gestureListener = new GestureDetector.SimpleOnGestureListener(){
        @Override
        public boolean onSingleTapConfirmed(MotionEvent e) {
            for (UnderlayButton button : buttons){
                if(button.onClick(e.getX(), e.getY()))
                    break;
            }

            return true;
        }
    };

    private View.OnTouchListener onTouchListener = new View.OnTouchListener() {
        @Override
        public boolean onTouch(View view, MotionEvent e) {
            if (swipedPos < 0) return false;
            Point point = new Point((int) e.getRawX(), (int) e.getRawY());

            RecyclerView.ViewHolder swipedViewHolder = recyclerView.findViewHolderForAdapterPosition(swipedPos);
            View swipedItem = swipedViewHolder.itemView;
            Rect rect = new Rect();
            swipedItem.getGlobalVisibleRect(rect);

            if (e.getAction() == MotionEvent.ACTION_DOWN || e.getAction() == MotionEvent.ACTION_UP ||e.getAction() == MotionEvent.ACTION_MOVE) {
                if (rect.top < point.y && rect.bottom > point.y)
                    gestureDetector.onTouchEvent(e);
                else {
                    recoverQueue.add(swipedPos);
                    swipedPos = -1;
                    recoverSwipedItem();
                }
            }
            return false;
        }
    };

    public SwipeHelper(Context context, RecyclerView recyclerView) {
        super(0, ItemTouchHelper.LEFT);
        this.recyclerView = recyclerView;
        this.buttons = new ArrayList<>();
        this.gestureDetector = new GestureDetector(context, gestureListener);
        this.recyclerView.setOnTouchListener(onTouchListener);
        buttonsBuffer = new HashMap<>();
        recoverQueue = new LinkedList<Integer>(){
            @Override
            public boolean add(Integer o) {
                if (contains(o))
                    return false;
                else
                    return super.add(o);
            }
        };

        attachSwipe();
    }


    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        return false;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        int pos = viewHolder.getAdapterPosition();

        if (swipedPos != pos)
            recoverQueue.add(swipedPos);

        swipedPos = pos;

        if (buttonsBuffer.containsKey(swipedPos))
            buttons = buttonsBuffer.get(swipedPos);
        else
            buttons.clear();

        buttonsBuffer.clear();
        swipeThreshold = 0.5f * buttons.size() * BUTTON_WIDTH;
        recoverSwipedItem();
    }

    @Override
    public float getSwipeThreshold(RecyclerView.ViewHolder viewHolder) {
        return swipeThreshold;
    }

    @Override
    public float getSwipeEscapeVelocity(float defaultValue) {
        return 0.1f * defaultValue;
    }

    @Override
    public float getSwipeVelocityThreshold(float defaultValue) {
        return 5.0f * defaultValue;
    }

    @Override
    public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        int pos = viewHolder.getAdapterPosition();
        float translationX = dX;
        View itemView = viewHolder.itemView;

        if (pos < 0){
            swipedPos = pos;
            return;
        }

        if(actionState == ItemTouchHelper.ACTION_STATE_SWIPE){
            if(dX < 0) {
                List<UnderlayButton> buffer = new ArrayList<>();

                if (!buttonsBuffer.containsKey(pos)){
                    instantiateUnderlayButton(viewHolder, buffer);
                    buttonsBuffer.put(pos, buffer);
                }
                else {
                    buffer = buttonsBuffer.get(pos);
                }

                translationX = dX * buffer.size() * BUTTON_WIDTH / itemView.getWidth();
                drawButtons(c, itemView, buffer, pos, translationX);
            }
        }

        super.onChildDraw(c, recyclerView, viewHolder, translationX, dY, actionState, isCurrentlyActive);
    }

    private synchronized void recoverSwipedItem(){
        while (!recoverQueue.isEmpty()){
            int pos = recoverQueue.poll();
            if (pos > -1) {
                recyclerView.getAdapter().notifyItemChanged(pos);
            }
        }
    }

    private void drawButtons(Canvas c, View itemView, List<UnderlayButton> buffer, int pos, float dX){
        float right = itemView.getRight();
        float dButtonWidth = (-1) * dX / buffer.size();

        for (UnderlayButton button : buffer) {
            float left = right - dButtonWidth;
            button.onDraw(
                    c,
                    new RectF(
                            left,
                            itemView.getTop(),
                            right,
                            itemView.getBottom()
                    ),
                    pos
            );

            right = left;
        }
    }

    public void attachSwipe(){
        ItemTouchHelper itemTouchHelper = new ItemTouchHelper(this);
        itemTouchHelper.attachToRecyclerView(recyclerView);
    }

    public abstract void instantiateUnderlayButton(RecyclerView.ViewHolder viewHolder, List<UnderlayButton> underlayButtons);

    public static class UnderlayButton {
        private String text;
        private int imageResId;
        private int color;
        private int pos;
        private RectF clickRegion;
        private UnderlayButtonClickListener clickListener;

        public UnderlayButton(String text, int imageResId, int color, UnderlayButtonClickListener clickListener) {
            this.text = text;
            this.imageResId = imageResId;
            this.color = color;
            this.clickListener = clickListener;
        }

        public boolean onClick(float x, float y){
            if (clickRegion != null && clickRegion.contains(x, y)){
                clickListener.onClick(pos);
                return true;
            }

            return false;
        }

        public void onDraw(Canvas c, RectF rect, int pos){
            Paint p = new Paint();

            // Draw background
            p.setColor(color);
            c.drawRect(rect, p);

            // Draw Text
            p.setColor(Color.WHITE);
            p.setTextSize(LayoutHelper.getPx(MyApplication.getAppContext(), 12));

            Rect r = new Rect();
            float cHeight = rect.height();
            float cWidth = rect.width();
            p.setTextAlign(Paint.Align.LEFT);
            p.getTextBounds(text, 0, text.length(), r);
            float x = cWidth / 2f - r.width() / 2f - r.left;
            float y = cHeight / 2f + r.height() / 2f - r.bottom;
            c.drawText(text, rect.left + x, rect.top + y, p);

            clickRegion = rect;
            this.pos = pos;
        }
    }

    public interface UnderlayButtonClickListener {
        void onClick(int pos);
    }
}

Usage:

SwipeHelper swipeHelper = new SwipeHelper(this, recyclerView) {
    @Override
    public void instantiateUnderlayButton(RecyclerView.ViewHolder viewHolder, List<UnderlayButton> underlayButtons) {
        underlayButtons.add(new SwipeHelper.UnderlayButton(
                "Delete",
                0,
                Color.parseColor("#FF3C30"),
                new SwipeHelper.UnderlayButtonClickListener() {
                    @Override
                    public void onClick(int pos) {
                        // TODO: onDelete
                    }
                }
        ));

        underlayButtons.add(new SwipeHelper.UnderlayButton(
                "Transfer",
                0,
                Color.parseColor("#FF9502"),
                new SwipeHelper.UnderlayButtonClickListener() {
                    @Override
                    public void onClick(int pos) {
                        // TODO: OnTransfer
                    }
                }
        ));
        underlayButtons.add(new SwipeHelper.UnderlayButton(
                "Unshare",
                0,
                Color.parseColor("#C7C7CB"),
                new SwipeHelper.UnderlayButtonClickListener() {
                    @Override
                    public void onClick(int pos) {
                        // TODO: OnUnshare
                    }
                }
        ));
    }
};

Note: This helper class is designed for left swipe. You can change swipe direction in SwipeHelper's constructor, and making changes based on dX in onChildDraw method accordingly.

If you want to show image in the button, just make the use of imageResId in UnderlayButton, and re-implement the onDraw method.

There is a known bug, when you swipe an item diagonally from one item to another, the first touched item will flash a little. This could be addressed by decreasing the value of getSwipeVelocityThreshold, but this makes harder for user to swipe the item. You can also adjust the swiping feeling by changing two other values in getSwipeThreshold and getSwipeEscapeVelocity. Check into the ItemTouchHelper source code, the comments are very helpful.

I believe there is a lot place for optimization. This solution just gives an idea if you want to stick with ItemTouchHelper. Please let me know if you have problem using it. Below is a screenshot.

Acknowledgment: this solution is mostly inspired from AdamWei's answer in this post

Answer 2

Here is the Kotlin version based on the accepted answer approach. With some minor changes I managed to render the buttons width based on the intrinsic size of the text instead of using a fixed width.

Demo project: https://github.com/ntnhon/RecyclerViewRowOptionsDemo

Implementation of SwipeHelper:

import android.annotation.SuppressLint
import android.content.Context
import android.graphics.*
import android.view.MotionEvent
import android.view.View
import androidx.annotation.ColorRes
import androidx.core.content.ContextCompat
import androidx.recyclerview.widget.ItemTouchHelper
import androidx.recyclerview.widget.RecyclerView
import java.util.*
import kotlin.math.abs
import kotlin.math.max

abstract class SwipeHelper(
    private val recyclerView: RecyclerView
) : ItemTouchHelper.SimpleCallback(
    ItemTouchHelper.ACTION_STATE_IDLE,
    ItemTouchHelper.LEFT
) {
    private var swipedPosition = -1
    private val buttonsBuffer: MutableMap<Int, List<UnderlayButton>> = mutableMapOf()
    private val recoverQueue = object : LinkedList<Int>() {
        override fun add(element: Int): Boolean {
            if (contains(element)) return false
            return super.add(element)
        }
    }

    @SuppressLint("ClickableViewAccessibility")
    private val touchListener = View.OnTouchListener { _, event ->
        if (swipedPosition < 0) return@OnTouchListener false
        buttonsBuffer[swipedPosition]?.forEach { it.handle(event) }
        recoverQueue.add(swipedPosition)
        swipedPosition = -1
        recoverSwipedItem()
        true
    }

    init {
        recyclerView.setOnTouchListener(touchListener)
    }

    private fun recoverSwipedItem() {
        while (!recoverQueue.isEmpty()) {
            val position = recoverQueue.poll() ?: return
            recyclerView.adapter?.notifyItemChanged(position)
        }
    }

    private fun drawButtons(
        canvas: Canvas,
        buttons: List<UnderlayButton>,
        itemView: View,
        dX: Float
    ) {
        var right = itemView.right
        buttons.forEach { button ->
            val width = button.intrinsicWidth / buttons.intrinsicWidth() * abs(dX)
            val left = right - width
            button.draw(
                canvas,
                RectF(left, itemView.top.toFloat(), right.toFloat(), itemView.bottom.toFloat())
            )

            right = left.toInt()
        }
    }

    override fun onChildDraw(
        c: Canvas,
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        dX: Float,
        dY: Float,
        actionState: Int,
        isCurrentlyActive: Boolean
    ) {
        val position = viewHolder.adapterPosition
        var maxDX = dX
        val itemView = viewHolder.itemView

        if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
            if (dX < 0) {
                if (!buttonsBuffer.containsKey(position)) {
                    buttonsBuffer[position] = instantiateUnderlayButton(position)
                }

                val buttons = buttonsBuffer[position] ?: return
                if (buttons.isEmpty()) return
                maxDX = max(-buttons.intrinsicWidth(), dX)
                drawButtons(c, buttons, itemView, maxDX)
            }
        }

        super.onChildDraw(
            c,
            recyclerView,
            viewHolder,
            maxDX,
            dY,
            actionState,
            isCurrentlyActive
        )
    }

    override fun onMove(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        target: RecyclerView.ViewHolder
    ): Boolean {
        return false
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        val position = viewHolder.adapterPosition
        if (swipedPosition != position) recoverQueue.add(swipedPosition)
        swipedPosition = position
        recoverSwipedItem()
    }

    abstract fun instantiateUnderlayButton(position: Int): List<UnderlayButton>

    //region UnderlayButton
    interface UnderlayButtonClickListener {
        fun onClick()
    }

    class UnderlayButton(
        private val context: Context,
        private val title: String,
        textSize: Float,
        @ColorRes private val colorRes: Int,
        private val clickListener: UnderlayButtonClickListener
    ) {
        private var clickableRegion: RectF? = null
        private val textSizeInPixel: Float = textSize * context.resources.displayMetrics.density // dp to px
        private val horizontalPadding = 50.0f
        val intrinsicWidth: Float

        init {
            val paint = Paint()
            paint.textSize = textSizeInPixel
            paint.typeface = Typeface.DEFAULT_BOLD
            paint.textAlign = Paint.Align.LEFT
            val titleBounds = Rect()
            paint.getTextBounds(title, 0, title.length, titleBounds)
            intrinsicWidth = titleBounds.width() + 2 * horizontalPadding
        }

        fun draw(canvas: Canvas, rect: RectF) {
            val paint = Paint()

            // Draw background
            paint.color = ContextCompat.getColor(context, colorRes)
            canvas.drawRect(rect, paint)

            // Draw title
            paint.color = ContextCompat.getColor(context, android.R.color.white)
            paint.textSize = textSizeInPixel
            paint.typeface = Typeface.DEFAULT_BOLD
            paint.textAlign = Paint.Align.LEFT

            val titleBounds = Rect()
            paint.getTextBounds(title, 0, title.length, titleBounds)

            val y = rect.height() / 2 + titleBounds.height() / 2 - titleBounds.bottom
            canvas.drawText(title, rect.left + horizontalPadding, rect.top + y, paint)

            clickableRegion = rect
        }

        fun handle(event: MotionEvent) {
            clickableRegion?.let {
                if (it.contains(event.x, event.y)) {
                    clickListener.onClick()
                }
            }
        }
    }
    //endregion
}

private fun List<SwipeHelper.UnderlayButton>.intrinsicWidth(): Float {
    if (isEmpty()) return 0.0f
    return map { it.intrinsicWidth }.reduce { acc, fl -> acc + fl }
}

Usage:

private fun setUpRecyclerView() {
        binding.recyclerView.adapter = Adapter(listOf(
            "Item 0: No action",
            "Item 1: Delete",
            "Item 2: Delete & Mark as unread",
            "Item 3: Delete, Mark as unread & Archive"
        ))
        binding.recyclerView.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))
        binding.recyclerView.layoutManager = LinearLayoutManager(this)

        val itemTouchHelper = ItemTouchHelper(object : SwipeHelper(binding.recyclerView) {
            override fun instantiateUnderlayButton(position: Int): List<UnderlayButton> {
                var buttons = listOf<UnderlayButton>()
                val deleteButton = deleteButton(position)
                val markAsUnreadButton = markAsUnreadButton(position)
                val archiveButton = archiveButton(position)
                when (position) {
                    1 -> buttons = listOf(deleteButton)
                    2 -> buttons = listOf(deleteButton, markAsUnreadButton)
                    3 -> buttons = listOf(deleteButton, markAsUnreadButton, archiveButton)
                    else -> Unit
                }
                return buttons
            }
        })

        itemTouchHelper.attachToRecyclerView(binding.recyclerView)
    }

    private fun toast(text: String) {
        toast?.cancel()
        toast = Toast.makeText(this, text, Toast.LENGTH_SHORT)
        toast?.show()
    }

    private fun deleteButton(position: Int) : SwipeHelper.UnderlayButton {
        return SwipeHelper.UnderlayButton(
            this,
            "Delete",
            14.0f,
            android.R.color.holo_red_light,
            object : SwipeHelper.UnderlayButtonClickListener {
                override fun onClick() {
                    toast("Deleted item $position")
                }
            })
    }

    private fun markAsUnreadButton(position: Int) : SwipeHelper.UnderlayButton {
        return SwipeHelper.UnderlayButton(
            this,
            "Mark as unread",
            14.0f,
            android.R.color.holo_green_light,
            object : SwipeHelper.UnderlayButtonClickListener {
                override fun onClick() {
                    toast("Marked as unread item $position")
                }
            })
    }

    private fun archiveButton(position: Int) : SwipeHelper.UnderlayButton {
        return SwipeHelper.UnderlayButton(
            this,
            "Archive",
            14.0f,
            android.R.color.holo_blue_light,
            object : SwipeHelper.UnderlayButtonClickListener {
                override fun onClick() {
                    toast("Archived item $position")
                }
            })
    }