1/*
2 * Copyright (C) 2013 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 */
16package com.android.dreams.phototable;
17
18import android.content.Context;
19import android.content.res.Resources;
20import android.view.MotionEvent;
21
22/**
23 * Detect and dispatch edge events.
24 */
25public class DragGestureDetector {
26    @SuppressWarnings("unused")
27    private static final String TAG = "DragGestureDetector";
28
29    private final PhotoTable mTable;
30    private final float mTouchGain;
31
32    private float[] mLast;
33    private float[] mCurrent;
34    private boolean mDrag;
35
36    public DragGestureDetector(Context context, PhotoTable table) {
37        Resources res = context.getResources();
38        mTouchGain = res.getInteger(R.integer.generalized_touch_gain) / 1000000f;
39        mTable = table;
40        mLast = new float[2];
41        mCurrent = new float[2];
42    }
43
44    private void computeAveragePosition(MotionEvent event, float[] position) {
45        computeAveragePosition(event, position, -1);
46    }
47
48    private void computeAveragePosition(MotionEvent event, float[] position, int ignore) {
49        final int pointerCount = event.getPointerCount();
50        position[0] = 0f;
51        position[1] = 0f;
52        float count = 0f;
53        for (int p = 0; p < pointerCount; p++) {
54            if (p != ignore) {
55                position[0] += event.getX(p);
56                position[1] += event.getY(p);
57                count += 1f;
58            }
59        }
60        position[0] /= count;
61        position[1] /= count;
62    }
63
64    public boolean onTouchEvent(MotionEvent event) {
65        int index = event.getActionIndex();
66        switch (event.getActionMasked()) {
67            case MotionEvent.ACTION_DOWN:
68                computeAveragePosition(event, mLast);
69                mDrag = false;
70                break;
71
72            case MotionEvent.ACTION_POINTER_DOWN:
73                mDrag = mTable.hasFocus();
74                computeAveragePosition(event, mLast);
75                break;
76
77            case MotionEvent.ACTION_POINTER_UP:
78                computeAveragePosition(event, mLast, index);
79                break;
80
81            case MotionEvent.ACTION_MOVE:
82                computeAveragePosition(event, mCurrent);
83                if (mDrag) {
84                    move(event, false);
85                }
86                break;
87
88            case MotionEvent.ACTION_CANCEL:
89            case MotionEvent.ACTION_UP:
90                if (mDrag) {
91                    move(event, true);
92                }
93                mDrag = false;
94                break;
95        }
96
97        if (mDrag) {
98            mTable.refreshFocus();
99        }
100
101        return mDrag;
102    }
103
104    private void move(MotionEvent event, boolean drop) {
105        mTable.move(mTable.getFocus(),
106                mTouchGain * (mCurrent[0] - mLast[0]),
107                mTouchGain * (mCurrent[1] - mLast[1]),
108                drop);
109        mLast[0] = mCurrent[0];
110        mLast[1] = mCurrent[1];
111    }
112}
113
114