1 /*
2  * Copyright (C) 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.android.deskclock;
18 
19 import android.content.Context;
20 import android.support.v4.view.ViewPager;
21 import android.util.AttributeSet;
22 import android.view.MotionEvent;
23 import android.view.View;
24 
25 public class VerticalViewPager extends ViewPager {
26 
VerticalViewPager(Context context)27     public VerticalViewPager(Context context) {
28         this(context, null);
29     }
30 
VerticalViewPager(Context context, AttributeSet attrs)31     public VerticalViewPager(Context context, AttributeSet attrs) {
32         super(context, attrs);
33         init();
34     }
35 
36     /**
37      * @return {@code false} since a vertical view pager can never be scrolled horizontally
38      */
39     @Override
canScrollHorizontally(int direction)40     public boolean canScrollHorizontally(int direction) {
41         return false;
42     }
43 
44     /**
45      * @return {@code true} iff a normal view pager would support horizontal scrolling at this time
46      */
47     @Override
canScrollVertically(int direction)48     public boolean canScrollVertically(int direction) {
49         return super.canScrollHorizontally(direction);
50     }
51 
init()52     private void init() {
53         // Make page transit vertical
54         setPageTransformer(true, new VerticalPageTransformer());
55         // Get rid of the overscroll drawing that happens on the left and right (the ripple)
56         setOverScrollMode(View.OVER_SCROLL_NEVER);
57     }
58 
59     @Override
onInterceptTouchEvent(MotionEvent ev)60     public boolean onInterceptTouchEvent(MotionEvent ev) {
61         final boolean toIntercept = super.onInterceptTouchEvent(flipXY(ev));
62         // Return MotionEvent to normal
63         flipXY(ev);
64         return toIntercept;
65     }
66 
67     @Override
onTouchEvent(MotionEvent ev)68     public boolean onTouchEvent(MotionEvent ev) {
69         final boolean toHandle = super.onTouchEvent(flipXY(ev));
70         // Return MotionEvent to normal
71         flipXY(ev);
72         return toHandle;
73     }
74 
flipXY(MotionEvent ev)75     private MotionEvent flipXY(MotionEvent ev) {
76         final float width = getWidth();
77         final float height = getHeight();
78 
79         final float x = (ev.getY() / height) * width;
80         final float y = (ev.getX() / width) * height;
81 
82         ev.setLocation(x, y);
83 
84         return ev;
85     }
86 
87     private static final class VerticalPageTransformer implements ViewPager.PageTransformer {
88         @Override
transformPage(View view, float position)89         public void transformPage(View view, float position) {
90             final int pageWidth = view.getWidth();
91             final int pageHeight = view.getHeight();
92             if (position < -1) {
93                 // This page is way off-screen to the left.
94                 view.setAlpha(0);
95             } else if (position <= 1) {
96                 view.setAlpha(1);
97                 // Counteract the default slide transition
98                 view.setTranslationX(pageWidth * -position);
99                 // set Y position to swipe in from top
100                 float yPosition = position * pageHeight;
101                 view.setTranslationY(yPosition);
102             } else {
103                 // This page is way off-screen to the right.
104                 view.setAlpha(0);
105             }
106         }
107     }
108 }
109