93 lines
3.3 KiB
Java
93 lines
3.3 KiB
Java
/*
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* Copyright (C) 2016 Piotr Wittchen
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.mian.gitnex.helpers;
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import androidx.annotation.NonNull;
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import androidx.recyclerview.widget.LinearLayoutManager;
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import androidx.recyclerview.widget.RecyclerView;
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/**
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* InfiniteScrollListener, which can be added to RecyclerView with addOnScrollListener
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* to detect moment when RecyclerView was scrolled to the end.
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*/
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public abstract class InfiniteScrollListener extends RecyclerView.OnScrollListener {
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private final int maxItemsPerRequest;
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private final LinearLayoutManager layoutManager;
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/**
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* Initializes InfiniteScrollListener, which can be added
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* to RecyclerView with addOnScrollListener method
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*
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* @param maxItemsPerRequest Max items to be loaded in a single request.
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* @param layoutManager LinearLayoutManager created in the Activity.
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*/
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public InfiniteScrollListener(int maxItemsPerRequest, LinearLayoutManager layoutManager) {
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assert maxItemsPerRequest > 0;
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assert layoutManager != null;
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this.maxItemsPerRequest = maxItemsPerRequest;
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this.layoutManager = layoutManager;
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}
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/**
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* Callback method to be invoked when the RecyclerView has been scrolled
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*
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* @param recyclerView The RecyclerView which scrolled.
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* @param dx The amount of horizontal scroll.
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* @param dy The amount of vertical scroll.
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*/
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@Override public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
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super.onScrolled(recyclerView, dx, dy);
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if (canLoadMoreItems()) {
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onScrolledToEnd(layoutManager.findFirstVisibleItemPosition());
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}
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}
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/**
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* Refreshes RecyclerView by setting new adapter,
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* calling invalidate method and scrolling to given position
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*
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* @param view RecyclerView to be refreshed
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* @param adapter adapter with new list of items to be loaded
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* @param position position to which RecyclerView will be scrolled
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*/
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protected void refreshView(RecyclerView view, RecyclerView.Adapter adapter, int position) {
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view.setAdapter(adapter);
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view.invalidate();
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view.scrollToPosition(position);
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}
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/**
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* Checks if more items can be loaded to the RecyclerView
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*
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* @return boolean Returns true if can load more items or false if not.
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*/
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protected boolean canLoadMoreItems() {
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final int visibleItemsCount = layoutManager.getChildCount();
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final int totalItemsCount = layoutManager.getItemCount();
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final int pastVisibleItemsCount = layoutManager.findFirstVisibleItemPosition();
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final boolean lastItemShown = visibleItemsCount + pastVisibleItemsCount >= totalItemsCount;
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return lastItemShown && totalItemsCount >= maxItemsPerRequest;
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}
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/**
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* Callback method to be invoked when the RecyclerView has been scrolled to the end
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*
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* @param firstVisibleItemPosition Id of the first visible item on the list.
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*/
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public abstract void onScrolledToEnd(final int firstVisibleItemPosition);
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}
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