space-android/src/main/java/com/owncloud/android/ui/EmptyRecyclerView.java

/*
 * Nextcloud Android client application
 *
 * @author Tobias Kaminsky
 * Copyright (C) 2018 Tobias Kaminsky
 * Copyright (C) 2018 Nextcloud GmbH.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package com.owncloud.android.ui;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;

import androidx.annotation.Nullable;
import androidx.recyclerview.widget.RecyclerView;

/**
 * Extends RecyclerView to show a custom view if no data is available
 * Inspired by http://alexzh.com/tutorials/how-to-setemptyview-to-recyclerview
 */
public class EmptyRecyclerView extends RecyclerView {
    private View mEmptyView;
    private boolean hasFooter = false;

    public EmptyRecyclerView(Context context) {
        super(context);
    }

    public EmptyRecyclerView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public EmptyRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void setAdapter(Adapter adapter) {
        Adapter oldAdapter = getAdapter();
        super.setAdapter(adapter);
        if (oldAdapter != null) {
            oldAdapter.unregisterAdapterDataObserver(observer);
        }
        if (adapter != null) {
            adapter.registerAdapterDataObserver(observer);
        }
    }

    public void setEmptyView(View view) {
        this.mEmptyView = view;
        initEmptyView();
    }

    private void initEmptyView() {
        if (mEmptyView != null) {
            int emptyCount = hasFooter ? 1 : 0;
            boolean empty = getAdapter() == null || getAdapter().getItemCount() == emptyCount;
            mEmptyView.setVisibility(empty ? VISIBLE : GONE);
            this.setVisibility(empty ? GONE : VISIBLE);
        }
    }

    private final AdapterDataObserver observer = new AdapterDataObserver() {
        @Override
        public void onChanged() {
            super.onChanged();
            initEmptyView();
        }

        @Override
        public void onItemRangeInserted(int positionStart, int itemCount) {
            super.onItemRangeInserted(positionStart, itemCount);
            initEmptyView();
        }

        @Override
        public void onItemRangeRemoved(int positionStart, int itemCount) {
            super.onItemRangeRemoved(positionStart, itemCount);
            initEmptyView();
        }
    };

    public void setHasFooter(boolean bool) {
        hasFooter = bool;
    }
}