SwipeRefreshListFragment.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 com.meg7.soas.ui.fragment;

import android.app.ListFragment;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.SwipeRefreshLayout;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;

import com.meg7.soas.util.SdkUtils;

/**
 * Subclass of {@link 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}.
 */
// Based on https://developer.android.com/samples/SwipeRefreshListFragment/src/com.example.android.swiperefreshlistfragment/SwipeRefreshListFragment.html
public class SwipeRefreshListFragment extends ListFragment {

    private SwipeRefreshLayout mSwipeRefreshLayout;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        // Create the list fragment's content view by calling the super method.
        final View listFragmentView = super.onCreateView(inflater, container, savedInstanceState);

        // 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)
        );

        // 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(android.support.v4.widget.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}.
     *
     * @see android.support.v4.widget.SwipeRefreshLayout#setColorScheme(int...).
     */
    public void setColorScheme(int colorRes1, int colorRes2, int colorRes3, int colorRes4) {
        mSwipeRefreshLayout.setColorScheme(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(android.view.LayoutInflater, android.view.ViewGroup, android.os.Bundle)}
     * which is a {@link android.view.ViewGroup}.
     * <p/>
     * <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 class ListFragmentSwipeRefreshLayout extends SwipeRefreshLayout {

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

        /**
         * 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() {
            final ListView listView = getListView();
            if (listView.getVisibility() == View.VISIBLE) {
                return canListViewScrollUp(listView);
            } else {
                return false;
            }
        }

    }

    /**
     * Utility method to check whether a {@link ListView} can scroll up from it's current position.
     * Handles platform version differences, providing backwards compatible functionality where
     * needed.
     */
    private static boolean canListViewScrollUp(ListView listView) {
        if (SdkUtils.hasIceCreamSandwich()) {
            // For ICS and above we can call canScrollVertically() to determine this
            return ViewCompat.canScrollVertically(listView, -1);
        } else {
            // Pre-ICS we need to manually check the first visible item and the child view's top
            // value
            return listView.getChildCount() > 0 &&
                    (listView.getFirstVisiblePosition() > 0
                            || listView.getChildAt(0).getTop() < listView.getPaddingTop());
        }
    }

}