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/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License
*/
package com.android.incallui.answer.impl.classifier;
import android.util.ArrayMap;
import android.view.MotionEvent;
import java.util.Map;
/**
* A classifier which looks at the speed and distance between successive points of a Stroke. It
* looks at two consecutive speeds between two points and calculates the ratio between them. The
* final result is the maximum of these values. It does the same for distances. If some speed or
* distance is equal to zero then the ratio between this and the next part is not calculated. To the
* duration of each part there is added one nanosecond so that it is always possible to calculate
* the speed of a part.
*/
class AccelerationClassifier extends StrokeClassifier {
private final Map<Stroke, Data> mStrokeMap = new ArrayMap<>();
public AccelerationClassifier(ClassifierData classifierData) {
mClassifierData = classifierData;
}
@Override
public String getTag() {
return "ACC";
}
@Override
public void onTouchEvent(MotionEvent event) {
int action = event.getActionMasked();
if (action == MotionEvent.ACTION_DOWN) {
mStrokeMap.clear();
}
for (int i = 0; i < event.getPointerCount(); i++) {
Stroke stroke = mClassifierData.getStroke(event.getPointerId(i));
Point point = stroke.getPoints().get(stroke.getPoints().size() - 1);
if (mStrokeMap.get(stroke) == null) {
mStrokeMap.put(stroke, new Data(point));
} else {
mStrokeMap.get(stroke).addPoint(point);
}
}
}
@Override
public float getFalseTouchEvaluation(Stroke stroke) {
Data data = mStrokeMap.get(stroke);
return 2 * SpeedRatioEvaluator.evaluate(data.maxSpeedRatio);
}
private static class Data {
static final float MILLIS_TO_NANOS = 1e6f;
Point previousPoint;
float previousSpeed = 0;
float maxSpeedRatio = 0;
public Data(Point point) {
previousPoint = point;
}
public void addPoint(Point point) {
float distance = previousPoint.dist(point);
float duration = (float) (point.timeOffsetNano - previousPoint.timeOffsetNano + 1);
float speed = distance / duration;
if (duration > 20 * MILLIS_TO_NANOS || duration < 5 * MILLIS_TO_NANOS) {
// reject this segment and ensure we won't use data about it in the next round.
previousSpeed = 0;
previousPoint = point;
return;
}
if (previousSpeed != 0.0f) {
maxSpeedRatio = Math.max(maxSpeedRatio, speed / previousSpeed);
}
previousSpeed = speed;
previousPoint = point;
}
}
}
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