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.ViewConfigurationCompat;
21import android.support.v4.view.ViewPager;
22import android.util.AttributeSet;
23import android.view.MotionEvent;
24import android.view.View;
25import android.view.ViewConfiguration;
26import android.view.ViewParent;
27
28public class VerticalViewPager extends ViewPager {
29    // TODO Remove the hack of using a parent view pager
30    private ViewPager mParentViewPager;
31    private float mLastMotionX;
32    private float mLastMotionY;
33    private float mTouchSlop;
34    private boolean mVerticalDrag;
35    private boolean mHorizontalDrag;
36
37    // Vertical transit page transformer
38    private final ViewPager.PageTransformer mPageTransformer = new ViewPager.PageTransformer() {
39        @Override
40        public void transformPage(View view, float position) {
41            final int pageWidth = view.getWidth();
42            final int pageHeight = view.getHeight();
43            if (position < -1) {
44                // This page is way off-screen to the left.
45                view.setAlpha(0);
46            } else if (position <= 1) {
47                view.setAlpha(1);
48                // Counteract the default slide transition
49                view.setTranslationX(pageWidth * -position);
50                // set Y position to swipe in from top
51                float yPosition = position * pageHeight;
52                view.setTranslationY(yPosition);
53            } else {
54                // This page is way off-screen to the right.
55                view.setAlpha(0);
56            }
57        }
58    };
59
60    public VerticalViewPager(Context context) {
61        super(context, null);
62    }
63
64    public VerticalViewPager(Context context, AttributeSet attrs) {
65        super(context, attrs);
66        final ViewConfiguration configuration = ViewConfiguration.get(context);
67        mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);
68        init();
69    }
70
71    private void init() {
72        // Make page transit vertical
73        setPageTransformer(true, mPageTransformer);
74        // Get rid of the overscroll drawing that happens on the left and right (the ripple)
75        setOverScrollMode(View.OVER_SCROLL_NEVER);
76    }
77
78    @Override
79    public boolean onTouchEvent(MotionEvent ev) {
80        try {
81            initializeParent();
82            final float x = ev.getX();
83            final float y = ev.getY();
84            switch (ev.getAction()) {
85                case MotionEvent.ACTION_DOWN: {
86                    mLastMotionX = x;
87                    mLastMotionY = y;
88                    if (!mParentViewPager.onTouchEvent(ev))
89                        return false;
90                    return verticalDrag(ev);
91                }
92                case MotionEvent.ACTION_MOVE: {
93                    final float xDiff = Math.abs(x - mLastMotionX);
94                    final float yDiff = Math.abs(y - mLastMotionY);
95                    if (!mHorizontalDrag && !mVerticalDrag) {
96                        if (xDiff > mTouchSlop && xDiff > yDiff) { // Swiping left and right
97                            mHorizontalDrag = true;
98                        } else if (yDiff > mTouchSlop && yDiff > xDiff) { //Swiping up and down
99                            mVerticalDrag = true;
100                        }
101                    }
102                    if (mHorizontalDrag) {
103                        return mParentViewPager.onTouchEvent(ev);
104                    } else if (mVerticalDrag) {
105                        return verticalDrag(ev);
106                    }
107                }
108                case MotionEvent.ACTION_UP: {
109                    if (mHorizontalDrag) {
110                        mHorizontalDrag = false;
111                        return mParentViewPager.onTouchEvent(ev);
112                    }
113                    if (mVerticalDrag) {
114                        mVerticalDrag = false;
115                        return verticalDrag(ev);
116                    }
117                }
118            }
119            // Set both flags to false in case user lifted finger in the parent view pager
120            mHorizontalDrag = false;
121            mVerticalDrag = false;
122        } catch (Exception e) {
123            // The mParentViewPager shouldn't be null, but just in case. If this happens,
124            // app should not crash, instead just ignore the user swipe input
125            // TODO: handle the exception gracefully
126        }
127        return false;
128    }
129
130    private void initializeParent() {
131        if (mParentViewPager == null) {
132            // This vertical view pager is nested in the frame layout inside the timer tab
133            // (fragment), which is nested inside the horizontal view pager. Therefore,
134            // it needs 3 layers to get all the way to the horizontal view pager.
135            final ViewParent parent = getParent().getParent().getParent();
136            if (parent instanceof ViewPager) {
137                mParentViewPager = (ViewPager) parent;
138            }
139        }
140    }
141
142    private boolean verticalDrag(MotionEvent ev) {
143        final float x = ev.getX();
144        final float y = ev.getY();
145        ev.setLocation(y, x);
146        return super.onTouchEvent(ev);
147    }
148}
149