SimpleItemTouchHelperCallback.java

package com.lin.poweradapter;

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

public class SimpleItemTouchHelperCallback extends ItemTouchHelper.Callback {

    public static final float ALPHA_FULL = 1.0f;

    private boolean longPressDragEnabled = false, swipeEnabled = false;

    private final ItemTouchHelperAdapter mAdapter;

    public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter) {
        this(adapter, false);
    }

    public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter, boolean longPressDragEnabled) {
        this(adapter, longPressDragEnabled, false);
    }

    public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter, boolean longPressDragEnabled, boolean swipeEnabled) {
        mAdapter = adapter;
        this.longPressDragEnabled = longPressDragEnabled;
        this.swipeEnabled = swipeEnabled;
    }

    public void setLongPressDragEnabled(boolean isLongPressDragEnabled) {
        this.longPressDragEnabled = isLongPressDragEnabled;
    }

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

    public void setSwipeEnabled(boolean isSwipeEnabled) {
        this.swipeEnabled = isSwipeEnabled;
    }

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

    @Override
    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        // Set movement flags based on the layout manager
        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;
        }

        // Notify the adapter of the move
        mAdapter.onItemMove(source.getAdapterPosition(), target.getAdapterPosition());
        return true;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {
        // Notify the adapter of the dismissal
        mAdapter.onItemDismiss(viewHolder.getAdapterPosition());
    }

    @Override
    public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
            // Fade out the view as it is swiped out of the parent's bounds
            final float alpha = ALPHA_FULL - Math.abs(dX) / (float) viewHolder.itemView.getWidth();
            viewHolder.itemView.setAlpha(alpha);
            viewHolder.itemView.setTranslationX(dX);
        } else {
            super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
        }
    }

    @Override
    public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
        // We only want the active item to change
        if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {
            if (viewHolder instanceof ItemTouchHelperViewHolder) {
                // Let the view holder know that this item is being moved or dragged
                ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
                itemViewHolder.onItemSelected();
            }
        }

        super.onSelectedChanged(viewHolder, actionState);
    }

    @Override
    public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        super.clearView(recyclerView, viewHolder);

        viewHolder.itemView.setAlpha(ALPHA_FULL);

        if (viewHolder instanceof ItemTouchHelperViewHolder) {
            // Tell the view holder it's time to restore the idle state
            ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
            itemViewHolder.onItemClear();
        }
    }
}