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      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 
     35     public MultiSwipeRefreshLayout(Context context) {
     36         super(context);
     37     }
     38 
     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      */
     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
     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      */
     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