1/*
2 * Copyright (C) 2016 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.incallui.answer.impl.classifier;
18
19import android.util.ArrayMap;
20import android.view.MotionEvent;
21import java.util.Map;
22
23/**
24 * A classifier which looks at the speed and distance between successive points of a Stroke. It
25 * looks at two consecutive speeds between two points and calculates the ratio between them. The
26 * final result is the maximum of these values. It does the same for distances. If some speed or
27 * distance is equal to zero then the ratio between this and the next part is not calculated. To the
28 * duration of each part there is added one nanosecond so that it is always possible to calculate
29 * the speed of a part.
30 */
31class AccelerationClassifier extends StrokeClassifier {
32  private final Map<Stroke, Data> mStrokeMap = new ArrayMap<>();
33
34  public AccelerationClassifier(ClassifierData classifierData) {
35    mClassifierData = classifierData;
36  }
37
38  @Override
39  public String getTag() {
40    return "ACC";
41  }
42
43  @Override
44  public void onTouchEvent(MotionEvent event) {
45    int action = event.getActionMasked();
46
47    if (action == MotionEvent.ACTION_DOWN) {
48      mStrokeMap.clear();
49    }
50
51    for (int i = 0; i < event.getPointerCount(); i++) {
52      Stroke stroke = mClassifierData.getStroke(event.getPointerId(i));
53      Point point = stroke.getPoints().get(stroke.getPoints().size() - 1);
54      if (mStrokeMap.get(stroke) == null) {
55        mStrokeMap.put(stroke, new Data(point));
56      } else {
57        mStrokeMap.get(stroke).addPoint(point);
58      }
59    }
60  }
61
62  @Override
63  public float getFalseTouchEvaluation(Stroke stroke) {
64    Data data = mStrokeMap.get(stroke);
65    return 2 * SpeedRatioEvaluator.evaluate(data.maxSpeedRatio);
66  }
67
68  private static class Data {
69
70    static final float MILLIS_TO_NANOS = 1e6f;
71
72    Point previousPoint;
73    float previousSpeed = 0;
74    float maxSpeedRatio = 0;
75
76    public Data(Point point) {
77      previousPoint = point;
78    }
79
80    public void addPoint(Point point) {
81      float distance = previousPoint.dist(point);
82      float duration = (float) (point.timeOffsetNano - previousPoint.timeOffsetNano + 1);
83      float speed = distance / duration;
84
85      if (duration > 20 * MILLIS_TO_NANOS || duration < 5 * MILLIS_TO_NANOS) {
86        // reject this segment and ensure we won't use data about it in the next round.
87        previousSpeed = 0;
88        previousPoint = point;
89        return;
90      }
91      if (previousSpeed != 0.0f) {
92        maxSpeedRatio = Math.max(maxSpeedRatio, speed / previousSpeed);
93      }
94
95      previousSpeed = speed;
96      previousPoint = point;
97    }
98  }
99}
100