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
17package com.android.deskclock;
18
19import android.content.Context;
20import android.support.v4.view.ViewPager;
21import android.util.AttributeSet;
22import android.view.MotionEvent;
23import android.view.View;
24
25public class VerticalViewPager extends ViewPager {
26
27    public VerticalViewPager(Context context) {
28        this(context, null);
29    }
30
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
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
48    public boolean canScrollVertically(int direction) {
49        return super.canScrollHorizontally(direction);
50    }
51
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
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
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
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
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