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 have a much simpler solution:

1. Add a button to your row XML, width 0, floating on the right:

> <Button
>     android:id="@+id/hidden"
>     android:layout_width="0dp"
>     android:layout_height="match_parent"
>     android:layout_alignParentRight = "true">

2. in onChildDraw(), just increase its width by the dX value.

    int position = viewHolder.getAdapterPosition();
    View v = recyclerView.getLayoutManager().findViewByPosition(position);
    Button hidden = v.findViewById(R.id.hidden);
    hidden.setLayoutParams(new LinearLayout.LayoutParams((int)-dX, -1));
   

Make sure not to call the default super.onChildDraw()

Answer 2

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 3

If you want button(s) on left side as well when swipe in the other direction, just try to add this simple lines in the existing answer:

1. In drawButtons method:

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

       for (UnderlayButton button : buffer) {
           if (dX < 0) {
               left = right - dButtonWidth;
               button.onDraw(
                       c,
                       new RectF(
                               left,
                               itemView.getTop(),
                               right,
                               itemView.getBottom()
                       ),
                       pos, dX //(to draw button on right)
               );
   
               right = left;
           } else if (dX > 0) {
               right = left - dButtonWidth;
               button.onDraw(c,
                       new RectF(
                               right,
                               itemView.getTop(),
                               left,
                               itemView.getBottom()
                       ), pos, dX //(to draw button on left)
               );
   
   
           }
       }
   }
   

2. In onDraw method check the value of dX and set text and colour of buttons:

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

           // Draw background
   
           if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
   
   
               if (dX > 0)
                   p.setColor(Color.parseColor("#23d2c5"));
               else if (dX < 0)
                   p.setColor(Color.parseColor("#23d2c5"));
   
               c.drawRect(rect, p);
   
   
               // Draw Text
               p.setColor(Color.WHITE);
               p.setTextSize(36);
               //  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;
               if (dX > 0) {
                   p.setColor(Color.parseColor("#23d2c5"));
                   c.drawText("Reject", rect.left + x, rect.top + y, p);
               } else if (dX < 0) {
   
                   c.drawText(text, rect.left + x, rect.top + y, p);
               }
               clickRegion = rect;
               this.pos = pos;
           }
   
       }
   

Answer 4

If you use a RecyclerView, try to use OnScrollListener. Do something like this.

 private class YourOnScrollListener extends RecyclerView.OnScrollListener {

    private boolean directionLeft;

    @Override
    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        if (newState == RecyclerView.SCROLL_STATE_IDLE) {
            if (directionLeft) drawButtons();
            //Draw buttons here if you want them to be drawn after scroll is finished
            //here you can play with states, to draw buttons or erase it whenever you want
        }
    }

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        if (dx < 0) directionLeft = true;
        else directionLeft = false;
    }

}

Answer 5

Following Wenxi Zeng's answer here, if you want to have the text in the buttons on multiple lines, replace UnderlayButton's onDraw method with this:

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

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

        // Draw Text
        TextPaint textPaint = new TextPaint();
        textPaint.setTextSize(UtilitiesOperations.convertDpToPx(getContext(), 15));
        textPaint.setColor(Color.WHITE);
        StaticLayout sl = new StaticLayout(text, textPaint, (int)rect.width(),
                Layout.Alignment.ALIGN_CENTER, 1, 1, false);

        canvas.save();
        Rect r = new Rect();
        float y = (rect.height() / 2f) + (r.height() / 2f) - r.bottom - (sl.getHeight() /2);
        canvas.translate(rect.left, rect.top + y);
        sl.draw(canvas);
        canvas.restore();

        clickRegion = rect;
        this.pos = pos;
    }

Answer 6

I wanted to use this touch gesture in my app too, after working too much with Itemtouchhelper I decided to write my own touch handler:

    private class TouchHelper : Java.Lang.Object, View.IOnTouchListener
    {
        ViewHolder vh;
        public TouchHelper(ViewHolder vh)
        { this.vh = vh;  }

        float DownX, DownY; bool isSliding;
        TimeSpan tsDown;
        public bool OnTouch(View v, MotionEvent e)
        {
            switch (e.Action)
            {
                case MotionEventActions.Down:
                    DownX = e.GetX(); DownY = e.GetY();
                    tsDown = TimeSpan.Now;
                    break;
                case MotionEventActions.Move:
                    float deltaX = e.GetX() - DownX, deltaY = e.GetX() - DownY;
                    if (Math.Abs(deltaX) >= Values.ScreenWidth / 20 || Math.Abs(deltaY) >= Values.ScreenWidth / 20)
                        isSliding = Math.Abs(deltaX) > Math.Abs(deltaY);

                    //TextsPlace is the layout that moves with touch
                    if(isSliding)
                        vh.TextsPlace.TranslationX = deltaX / 2;

                    break;
                case MotionEventActions.Cancel:
                case MotionEventActions.Up:
                    //handle if touch was for clicking
                    if (Math.Abs(deltaX) <= 50 && (TimeSpan.Now - tsDown).TotalMilliseconds <= 400)
                        vh.OnTextsPlaceClick(vh.TextsPlace, null);
                    break;
            }
            return true;
        }
    }

Note: Set this as ontouchlistener of your viewholder content when creating the viewholder. You can add your animations to return the item to its first place.

You can also write your custom layoutmanager to block vertical scroll while item is sliding.