SwipeRefreshRecyclerViewFragment.java

/*
 * Copyright 2014 The Android Open Source Project
 *
 * 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 org.gdg.frisbee.android.fragment;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;

import java.lang.ref.WeakReference;

import timber.log.Timber;

/**
 * Subclass of {@link android.support.v4.app.ListFragment} which provides automatic support for
 * providing the 'swipe-to-refresh' UX gesture by wrapping the the content view in a
 * {@link android.support.v4.widget.SwipeRefreshLayout}.
 */
public class SwipeRefreshRecyclerViewFragment extends GdgRecyclerFragment {

    private ListFragmentSwipeRefreshLayout mSwipeRefreshLayout;

    public View createSwipeRefresh(final View listFragmentView) {

        // Now create a SwipeRefreshLayout to wrap the fragment's content view
        mSwipeRefreshLayout = new ListFragmentSwipeRefreshLayout(getActivity());

        // Add the list fragment's content view to the SwipeRefreshLayout, making sure that it fills
        // the SwipeRefreshLayout
        mSwipeRefreshLayout.addView(listFragmentView,
                ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);

        // Make sure that the SwipeRefreshLayout will fill the fragment
        mSwipeRefreshLayout.setLayoutParams(
                new ViewGroup.LayoutParams(
                        ViewGroup.LayoutParams.MATCH_PARENT,
                        ViewGroup.LayoutParams.MATCH_PARENT));

        mSwipeRefreshLayout.getViewTreeObserver().addOnGlobalLayoutListener(
            new ViewTreeObserver.OnGlobalLayoutListener() {
                @Override
                public void onGlobalLayout() {
                    mSwipeRefreshLayout.getViewTreeObserver().removeOnGlobalLayoutListener(this);
                    mSwipeRefreshLayout.setRecyclerView(getListView());
                }
            });

        // Now return the SwipeRefreshLayout as this fragment's content view
        return mSwipeRefreshLayout;
    }

    /**
     * Set the {@link android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener} to listen for
     * initiated refreshes.
     *
     * @see android.support.v4.widget.SwipeRefreshLayout#setOnRefreshListener(SwipeRefreshLayout.OnRefreshListener)
     */
    public void setOnRefreshListener(SwipeRefreshLayout.OnRefreshListener listener) {
        mSwipeRefreshLayout.setOnRefreshListener(listener);
    }

    /**
     * Returns whether the {@link android.support.v4.widget.SwipeRefreshLayout} is currently
     * refreshing or not.
     *
     * @see android.support.v4.widget.SwipeRefreshLayout#isRefreshing()
     */
    public boolean isRefreshing() {
        return mSwipeRefreshLayout.isRefreshing();
    }

    /**
     * Set whether the {@link android.support.v4.widget.SwipeRefreshLayout} should be displaying
     * that it is refreshing or not.
     *
     * @see android.support.v4.widget.SwipeRefreshLayout#setRefreshing(boolean)
     */
    public void setRefreshing(boolean refreshing) {
        mSwipeRefreshLayout.setRefreshing(refreshing);
    }

    /**
     * Set the color scheme for the {@link android.support.v4.widget.SwipeRefreshLayout}.
     *
     */
    public void setColorSchemeResources(int colorRes1, int colorRes2, int colorRes3, int colorRes4) {
        mSwipeRefreshLayout.setColorSchemeResources(colorRes1, colorRes2, colorRes3, colorRes4);
    }

    /**
     * @return the fragment's {@link android.support.v4.widget.SwipeRefreshLayout} widget.
     */
    public SwipeRefreshLayout getSwipeRefreshLayout() {
        return mSwipeRefreshLayout;
    }

    /**
     * Sub-class of {@link android.support.v4.widget.SwipeRefreshLayout} for use in this
     * {@link android.support.v4.app.ListFragment}. The reason that this is needed is because
     * {@link android.support.v4.widget.SwipeRefreshLayout} only supports a single child, which it
     * expects to be the one which triggers refreshes. In our case the layout's child is the content
     * view returned from
     * {@link android.support.v4.app.ListFragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}
     * which is a {@link android.view.ViewGroup}.
     *
     * <p>To enable 'swipe-to-refresh' support via the {@link android.widget.ListView} we need to
     * override the default behavior and properly signal when a gesture is possible. This is done by
     * overriding {@link #canChildScrollUp()}.
     */
    private static class ListFragmentSwipeRefreshLayout extends SwipeRefreshLayout {

        private WeakReference<RecyclerView> recyclerView;

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

        public void setRecyclerView(RecyclerView recyclerView) {
            this.recyclerView = new WeakReference<>(recyclerView);
        }

        /**
         * As mentioned above, we need to override this method to properly signal when a
         * 'swipe-to-refresh' is possible.
         *
         * @return true if the {@link android.widget.ListView} is visible and can scroll up.
         */
        @Override
        public boolean canChildScrollUp() {
            RecyclerView view = recyclerView != null ? recyclerView.get() : null;

            return view != null
                    && view.getVisibility() == View.VISIBLE
                    && canListViewScrollUp(view);
        }


        /**
         * Utility method to check whether a {@link android.widget.ListView} can scroll up from it's current position.
         * Handles platform version differences, providing backwards compatible functionality where
         * needed.
         */
        private boolean canListViewScrollUp(RecyclerView recyclerView) {
            try {
                RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
                if (layoutManager instanceof LinearLayoutManager) {
                    int position = ((LinearLayoutManager) layoutManager).findFirstCompletelyVisibleItemPosition();
                    return position != 0;
                } else if (layoutManager instanceof StaggeredGridLayoutManager) {
                    int[] positions = ((StaggeredGridLayoutManager) layoutManager)
                        .findFirstCompletelyVisibleItemPositions(null);
                    for (int position : positions) {
                        if (position == 0) {
                            return false;
                        }
                    }
                }
            } catch (NullPointerException exception) {
                Timber.e(exception, "Exception in RecyclerView canListViewScrollUp.");
            }
            return true;
        }
    }

}