/*
* Copyright (C) 2017 Drakeet <drakeet.me@gmail.com>
*
* This file is part of rebase-android
*
* rebase-android is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* rebase-android is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with rebase-android. If not, see <http://www.gnu.org/licenses/>.
*/
package com.drakeet.rebase.tool;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
/**
* @author drakeet
*/
public class LoadMoreDelegate {
private final LoadMoreSubject loadMoreSubject;
public LoadMoreDelegate(LoadMoreSubject loadMoreSubject) {
this.loadMoreSubject = loadMoreSubject;
}
/**
* Should be called after recyclerView setup with its layoutManager and adapter
*
* @param recyclerView the RecyclerView
*/
public void attach(RecyclerView recyclerView) {
final LinearLayoutManager layoutManager
= (LinearLayoutManager) recyclerView.getLayoutManager();
recyclerView.addOnScrollListener(
new EndlessScrollListener(layoutManager, loadMoreSubject));
}
private static class EndlessScrollListener extends RecyclerView.OnScrollListener {
private static final int VISIBLE_THRESHOLD = 6;
private final LinearLayoutManager layoutManager;
private final LoadMoreSubject loadMoreSubject;
private EndlessScrollListener(LinearLayoutManager layoutManager, LoadMoreSubject loadMoreSubject) {
this.layoutManager = layoutManager;
this.loadMoreSubject = loadMoreSubject;
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
if (dy < 0 || loadMoreSubject.isLoading()) return;
final int itemCount = layoutManager.getItemCount();
final int lastVisiblePosition = layoutManager.findLastCompletelyVisibleItemPosition();
final boolean isBottom = (lastVisiblePosition >= itemCount - VISIBLE_THRESHOLD);
if (isBottom) {
loadMoreSubject.onLoadMore();
}
}
}
public interface LoadMoreSubject {
boolean isLoading();
void onLoadMore();
}
}