SwipeRefreshListFragment.java

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/*
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 * Copyright 2014 The Android Open Source Project
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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 com.example.android.swiperefreshlistfragment;
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import android.content.Context;
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import android.os.Bundle;
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import android.support.v4.app.ListFragment;
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import android.support.v4.view.ViewCompat;
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import android.support.v4.widget.SwipeRefreshLayout;
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import android.view.LayoutInflater;
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import android.view.View;
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import android.view.ViewGroup;
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import android.widget.ListView;
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/**
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 * Subclass of {@link android.support.v4.app.ListFragment} which provides automatic support for
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 * providing the 'swipe-to-refresh' UX gesture by wrapping the the content view in a
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 * {@link android.support.v4.widget.SwipeRefreshLayout}.
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 */
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public class SwipeRefreshListFragment extends ListFragment {
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    private SwipeRefreshLayout mSwipeRefreshLayout;
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    @Override
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    public View onCreateView(LayoutInflater inflater, ViewGroup container,
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            Bundle savedInstanceState) {
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        // Create the list fragment's content view by calling the super method
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        final View listFragmentView = super.onCreateView(inflater, container, savedInstanceState);
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        // Now create a SwipeRefreshLayout to wrap the fragment's content view
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        mSwipeRefreshLayout = new ListFragmentSwipeRefreshLayout(container.getContext());
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        // Add the list fragment's content view to the SwipeRefreshLayout, making sure that it fills
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        // the SwipeRefreshLayout
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        mSwipeRefreshLayout.addView(listFragmentView,
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                ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
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        // Make sure that the SwipeRefreshLayout will fill the fragment
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        mSwipeRefreshLayout.setLayoutParams(
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                new ViewGroup.LayoutParams(
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                        ViewGroup.LayoutParams.MATCH_PARENT,
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                        ViewGroup.LayoutParams.MATCH_PARENT));
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        // Now return the SwipeRefreshLayout as this fragment's content view
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        return mSwipeRefreshLayout;
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    }
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    /**
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     * Set the {@link android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener} to listen for
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     * initiated refreshes.
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     *
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     * @see android.support.v4.widget.SwipeRefreshLayout#setOnRefreshListener(android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener)
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     */
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    public void setOnRefreshListener(SwipeRefreshLayout.OnRefreshListener listener) {
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        mSwipeRefreshLayout.setOnRefreshListener(listener);
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    }
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    /**
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     * Returns whether the {@link android.support.v4.widget.SwipeRefreshLayout} is currently
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     * refreshing or not.
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     *
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     * @see android.support.v4.widget.SwipeRefreshLayout#isRefreshing()
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     */
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    public boolean isRefreshing() {
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        return mSwipeRefreshLayout.isRefreshing();
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    }
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    /**
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     * Set whether the {@link android.support.v4.widget.SwipeRefreshLayout} should be displaying
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     * that it is refreshing or not.
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     *
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     * @see android.support.v4.widget.SwipeRefreshLayout#setRefreshing(boolean)
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     */
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    public void setRefreshing(boolean refreshing) {
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        mSwipeRefreshLayout.setRefreshing(refreshing);
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    }
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    /**
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     * Set the color scheme for the {@link android.support.v4.widget.SwipeRefreshLayout}.
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     *
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     * @see android.support.v4.widget.SwipeRefreshLayout#setColorScheme(int, int, int, int)
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     */
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    public void setColorScheme(int colorRes1, int colorRes2, int colorRes3, int colorRes4) {
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        mSwipeRefreshLayout.setColorScheme(colorRes1, colorRes2, colorRes3, colorRes4);
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    }
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    /**
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     * @return the fragment's {@link android.support.v4.widget.SwipeRefreshLayout} widget.
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     */
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    public SwipeRefreshLayout getSwipeRefreshLayout() {
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        return mSwipeRefreshLayout;
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    }
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    /**
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     * Sub-class of {@link android.support.v4.widget.SwipeRefreshLayout} for use in this
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     * {@link android.support.v4.app.ListFragment}. The reason that this is needed is because
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     * {@link android.support.v4.widget.SwipeRefreshLayout} only supports a single child, which it
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     * expects to be the one which triggers refreshes. In our case the layout's child is the content
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     * view returned from
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     * {@link android.support.v4.app.ListFragment#onCreateView(android.view.LayoutInflater, android.view.ViewGroup, android.os.Bundle)}
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     * which is a {@link android.view.ViewGroup}.
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     *
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     * <p>To enable 'swipe-to-refresh' support via the {@link android.widget.ListView} we need to
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     * override the default behavior and properly signal when a gesture is possible. This is done by
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     * overriding {@link #canChildScrollUp()}.
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     */
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    private class ListFragmentSwipeRefreshLayout extends SwipeRefreshLayout {
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        public ListFragmentSwipeRefreshLayout(Context context) {
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            super(context);
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        }
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        /**
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         * As mentioned above, we need to override this method to properly signal when a
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         * 'swipe-to-refresh' is possible.
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         *
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         * @return true if the {@link android.widget.ListView} is visible and can scroll up.
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         */
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        @Override
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        public boolean canChildScrollUp() {
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            final ListView listView = getListView();
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            if (listView.getVisibility() == View.VISIBLE) {
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                return canListViewScrollUp(listView);
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            } else {
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                return false;
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            }
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        }
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    }
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    /**
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     * Utility method to check whether a {@link ListView} can scroll up from it's current position.
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     * Handles platform version differences, providing backwards compatible functionality where
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     * needed.
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     */
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    private static boolean canListViewScrollUp(ListView listView) {
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        if (android.os.Build.VERSION.SDK_INT >= 14) {
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            // For ICS and above we can call canScrollVertically() to determine this
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            return ViewCompat.canScrollVertically(listView, -1);
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        } else {
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            // Pre-ICS we need to manually check the first visible item and the child view's top
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            // value
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            return listView.getChildCount() > 0 &&
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                    (listView.getFirstVisiblePosition() > 0
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                            || listView.getChildAt(0).getTop() < listView.getPaddingTop());
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        }
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    }
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}