SimpleItemTouchHelperCallback.java

package com.fastaccess.ui.widgets.recyclerview.touch;

import android.graphics.Canvas;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.helper.ItemTouchHelper;
import android.view.View;

public class SimpleItemTouchHelperCallback extends ItemTouchHelper.Callback {

    public static final float ALPHA_FULL = 1.0f;

    private final ItemTouchHelperAdapter adapter;
    private boolean isSwipeable;

    public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter, boolean isSwipeable) {
        this.adapter = adapter;
        this.isSwipeable = isSwipeable;
    }

    @Override public boolean isLongPressDragEnabled() {
        return true;
    }

    @Override public boolean isItemViewSwipeEnabled() {
        return isSwipeable;
    }

    @Override public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        if (recyclerView.getLayoutManager() instanceof GridLayoutManager) {
            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
            final int swipeFlags = 0;
            return makeMovementFlags(dragFlags, swipeFlags);
        } else {
            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
            final int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;
            return makeMovementFlags(dragFlags, swipeFlags);
        }
    }

    @Override public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder source, RecyclerView.ViewHolder target) {
        if (source.getItemViewType() != target.getItemViewType()) {
            return false;
        }
        adapter.onItemMove(source.getAdapterPosition(), target.getAdapterPosition());
        return true;
    }

    @Override public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {
        if (viewHolder instanceof ItemTouchHelperViewHolder) {
            adapter.onItemDismiss(viewHolder.getAdapterPosition());
        }
    }

    @Override public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder,
                                      float dX, float dY, int actionState, boolean isCurrentlyActive) {
        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
        if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
            if (viewHolder instanceof ItemTouchHelperViewHolder) {
                View itemView = viewHolder.itemView;
                final float alpha = ALPHA_FULL - Math.abs(dX) / (float) itemView.getWidth();
                itemView.setAlpha(alpha);
            }
        }
    }

    @Override public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
        if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {
            if (viewHolder instanceof ItemTouchHelperViewHolder) {
                ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
                itemViewHolder.onItemSelected();
            }
        }
        super.onSelectedChanged(viewHolder, actionState);
    }

    @Override public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        super.clearView(recyclerView, viewHolder);
        if (viewHolder instanceof ItemTouchHelperViewHolder) {
            viewHolder.itemView.setAlpha(ALPHA_FULL);
            ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
            itemViewHolder.onItemClear();
        }
        adapter.onItemStoppedMoving();
    }
}