StackIndentationFunctor.java revision 67b2260093774f5866f781aede52830440f4ed0e 
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.systemui.statusbar.stack;
18
19/**
20 * A functor which can be queried for offset given the number of items before it.
21 */
22public abstract class StackIndentationFunctor {
23
24    protected final int mTotalTransitionDistance;
25    protected final int mDistanceToPeekStart;
26    protected int mMaxItemsInStack;
27    protected int mPeekSize;
28    protected boolean mStackStartsAtPeek;
29
30    /**
31     * @param maxItemsInStack The maximum number of items which should be visible at the same time,
32     *                        i.e the function returns totalTransitionDistance for the element with
33     *                        index maxItemsInStack
34     * @param peekSize The visual appearance of this is how far the cards in the stack peek
35     *                 out below the top card and it is measured in real pixels.
36     *                 Note that the visual appearance does not necessarily always correspond to
37     *                 the actual visual distance below the top card but is a maximum,
38     *                 achieved when the next card just starts transitioning into the stack and
39     *                 the stack is full.
40     *                 If totalTransitionDistance is equal to this, we directly start at the peek,
41     *                 otherwise the first element transitions between 0 and
42     *                 totalTransitionDistance - peekSize.
43     *                 Visualization:
44     *           ---------------------------------------------------   ---
45     *          |                                                   |   |
46     *          |                  FIRST ITEM                       |   | <- totalTransitionDistance
47     *          |                                                   |   |
48     *          |---------------------------------------------------|   |   ---
49     *          |__________________SECOND ITEM______________________|   |    |  <- peekSize
50     *          |===================================================|  _|_  _|_
51     *
52     * @param totalTransitionDistance The total transition distance an element has to go through
53     */
54    StackIndentationFunctor(int maxItemsInStack, int peekSize, int totalTransitionDistance) {
55        mTotalTransitionDistance = totalTransitionDistance;
56        mDistanceToPeekStart = mTotalTransitionDistance - peekSize;
57        mStackStartsAtPeek = mDistanceToPeekStart == 0;
58        mMaxItemsInStack = maxItemsInStack;
59        mPeekSize = peekSize;
60
61    }
62
63    public void setPeekSize(int mPeekSize) {
64        this.mPeekSize = mPeekSize;
65    }
66
67    /**
68     * Gets the offset of this Functor given a the quantity of items before it
69     *
70     * @param itemsBefore how many items are already in the stack before this element
71     * @return the offset
72     */
73    public abstract float getValue(float itemsBefore);
74}
75