1 /*
2  * Copyright 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *       http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.example.android.swiperefreshmultipleviews;
18 
19 import android.content.Context;
20 import android.support.v4.view.ViewCompat;
21 import android.support.v4.widget.SwipeRefreshLayout;
22 import android.util.AttributeSet;
23 import android.view.View;
24 import android.widget.AbsListView;
25 
26 /**
27  * A descendant of {@link android.support.v4.widget.SwipeRefreshLayout} which supports multiple
28  * child views triggering a refresh gesture. You set the views which can trigger the gesture via
29  * {@link #setSwipeableChildren(int...)}, providing it the child ids.
30  */
31 public class MultiSwipeRefreshLayout extends SwipeRefreshLayout {
32 
33     private View[] mSwipeableChildren;
34 
MultiSwipeRefreshLayout(Context context)35     public MultiSwipeRefreshLayout(Context context) {
36         super(context);
37     }
38 
MultiSwipeRefreshLayout(Context context, AttributeSet attrs)39     public MultiSwipeRefreshLayout(Context context, AttributeSet attrs) {
40         super(context, attrs);
41     }
42 
43     /**
44      * Set the children which can trigger a refresh by swiping down when they are visible. These
45      * views need to be a descendant of this view.
46      */
setSwipeableChildren(final int... ids)47     public void setSwipeableChildren(final int... ids) {
48         assert ids != null;
49 
50         // Iterate through the ids and find the Views
51         mSwipeableChildren = new View[ids.length];
52         for (int i = 0; i < ids.length; i++) {
53             mSwipeableChildren[i] = findViewById(ids[i]);
54         }
55     }
56 
57     // BEGIN_INCLUDE(can_child_scroll_up)
58     /**
59      * This method controls when the swipe-to-refresh gesture is triggered. By returning false here
60      * we are signifying that the view is in a state where a refresh gesture can start.
61      *
62      * <p>As {@link android.support.v4.widget.SwipeRefreshLayout} only supports one direct child by
63      * default, we need to manually iterate through our swipeable children to see if any are in a
64      * state to trigger the gesture. If so we return false to start the gesture.
65      */
66     @Override
canChildScrollUp()67     public boolean canChildScrollUp() {
68         if (mSwipeableChildren != null && mSwipeableChildren.length > 0) {
69             // Iterate through the scrollable children and check if any of them can not scroll up
70             for (View view : mSwipeableChildren) {
71                 if (view != null && view.isShown() && !canViewScrollUp(view)) {
72                     // If the view is shown, and can not scroll upwards, return false and start the
73                     // gesture.
74                     return false;
75                 }
76             }
77         }
78         return true;
79     }
80     // END_INCLUDE(can_child_scroll_up)
81 
82     // BEGIN_INCLUDE(can_view_scroll_up)
83     /**
84      * Utility method to check whether a {@link View} can scroll up from it's current position.
85      * Handles platform version differences, providing backwards compatible functionality where
86      * needed.
87      */
canViewScrollUp(View view)88     private static boolean canViewScrollUp(View view) {
89         if (android.os.Build.VERSION.SDK_INT >= 14) {
90             // For ICS and above we can call canScrollVertically() to determine this
91             return ViewCompat.canScrollVertically(view, -1);
92         } else {
93             if (view instanceof AbsListView) {
94                 // Pre-ICS we need to manually check the first visible item and the child view's top
95                 // value
96                 final AbsListView listView = (AbsListView) view;
97                 return listView.getChildCount() > 0 &&
98                         (listView.getFirstVisiblePosition() > 0
99                                 || listView.getChildAt(0).getTop() < listView.getPaddingTop());
100             } else {
101                 // For all other view types we just check the getScrollY() value
102                 return view.getScrollY() > 0;
103             }
104         }
105     }
106     // END_INCLUDE(can_view_scroll_up)
107 }
108