gistfile1.txt

/*
 * Copyright (C) 2015 Paul Burke
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.yocto.wenote.helper;

import android.graphics.Canvas;
import androidx.core.view.ViewCompat;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.ItemTouchHelper;

import com.yocto.wenote.Utils;
import com.yocto.wenote.load_more.LoadMoreSection;
import com.yocto.wenote.message.MessageSection;
import com.yocto.wenote.recyclerview.PaddingSection;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import io.github.luizgrp.sectionedrecyclerviewadapter.Section;
import io.github.luizgrp.sectionedrecyclerviewadapter.SectionedRecyclerViewAdapter;

import static com.yocto.wenote.Utils.trackEvent;

/**
 * An implementation of {@link ItemTouchHelper.Callback} that enables basic drag & drop and
 * swipe-to-dismiss. Drag events are automatically started by an item long-press.<br/>
 * </br/>
 * Expects the <code>RecyclerView.Adapter</code> to listen for {@link
 * ItemTouchHelperAdapter} callbacks and the <code>RecyclerView.ViewHolder</code> to implement
 * {@link ItemTouchHelperViewHolder}.
 *
 * @author Paul Burke (ipaulpro)
 */
public class SimpleItemTouchHelperCallback extends ItemTouchHelper.Callback {

    public static final float ALPHA_FULL = 1.0f;

    private final List<ItemTouchHelperAdapter> mAdapters;

    private boolean longPressDragEnabled = true;

    private final boolean showShadowDuringFirstPress;

    public SimpleItemTouchHelperCallback(boolean showShadowDuringFirstPress, ItemTouchHelperAdapter... adapters) {
        mAdapters = new ArrayList<>(Arrays.asList(adapters));
        this.showShadowDuringFirstPress = showShadowDuringFirstPress;
    }

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

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

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

    @Override
    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        if (SectionedRecyclerViewAdapter.VIEW_TYPE_ITEM_LOADED != SectionedRecyclerViewAdapter.getSectionItemViewTypeForAdapterViewType(viewHolder.getItemViewType())) {
            final int dragFlags = 0;
            final int swipeFlags = 0;
            return makeMovementFlags(dragFlags, swipeFlags);
        }

        final SectionedRecyclerViewAdapter sectionedRecyclerViewAdapter = (SectionedRecyclerViewAdapter)recyclerView.getAdapter();
        final int adapterPosition = viewHolder.getAdapterPosition();
        final int itemCount = sectionedRecyclerViewAdapter.getItemCount();
        if (adapterPosition < 0 || adapterPosition >= itemCount) {
            trackEvent("getMovementFlags", "fatal", adapterPosition + ">=" + itemCount);
            final int dragFlags = 0;
            final int swipeFlags = 0;
            return makeMovementFlags(dragFlags, swipeFlags);
        }

        Section section = sectionedRecyclerViewAdapter.getSectionForPosition(adapterPosition);

        if (section instanceof MessageSection || section instanceof PaddingSection || section instanceof LoadMoreSection) {
            final int dragFlags = 0;
            final int swipeFlags = 0;
            return makeMovementFlags(dragFlags, swipeFlags);
        }

        // Set movement flags based on the layout manager
        final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            // GridLayoutManager check should come before LinearLayoutManager, this is because
            // LinearLayoutManager is GridLayoutManager's based class.
            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
            final int swipeFlags = 0;
            return makeMovementFlags(dragFlags, swipeFlags);
        } else if (layoutManager instanceof LinearLayoutManager) {
            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
            final int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;
            return makeMovementFlags(dragFlags, swipeFlags);
        } else {
            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
            final int swipeFlags = 0;
            return makeMovementFlags(dragFlags, swipeFlags);
        }
    }

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

        final int fromPosition = source.getAdapterPosition();
        final int toPosition = target.getAdapterPosition();
        // Notify the adapter of the move
        for (ItemTouchHelperAdapter mAdapter : mAdapters) {
            if (mAdapter.onItemMove(fromPosition, toPosition)) {
                break;
            }
        }
        return true;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {
        // Notify the adapter of the dismissal
        for (ItemTouchHelperAdapter mAdapter : mAdapters) {
            mAdapter.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) {
            // 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);
            return;
        } else if (actionState == ItemTouchHelper.ACTION_STATE_DRAG) {
            if (isCurrentlyActive) {
                if (showShadowDuringFirstPress || dY != 0.0 || dX != 0.0) {
                    ViewCompat.setElevation(viewHolder.itemView, Utils.dpToPixelInFloat(4));
                }
            } else {
                if (dY == 0.0 && dX == 0.0) {
                    ViewCompat.setElevation(viewHolder.itemView, 0);
                }
            }
        }
    }

    @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);

        ViewCompat.setElevation(viewHolder.itemView, 0);

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