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/*
* Copyright (C) 2015 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.ArrayList;
import java.util.List;
import java.util.Map;
/**
* A classifier which for each point from a stroke, it creates a point on plane with coordinates
* (timeOffsetNano, distanceCoveredUpToThisPoint) (scaled by DURATION_SCALE and LENGTH_SCALE) and
* then it calculates the angle variance of these points like the class {@link AnglesClassifier}
* (without splitting it into two parts). The classifier ignores the last point of a stroke because
* the UP event comes in with some delay and this ruins the smoothness of this curve. Additionally,
* the classifier classifies calculates the percentage of angles which value is in [PI -
* ANGLE_DEVIATION, 2* PI) interval. The reason why the classifier does that is because the speed of
* a good stroke is most often increases, so most of these angels should be in this interval.
*/
class SpeedAnglesClassifier extends StrokeClassifier {
private Map<Stroke, Data> strokeMap = new ArrayMap<>();
public SpeedAnglesClassifier(ClassifierData classifierData) {
this.classifierData = classifierData;
}
@Override
public String getTag() {
return "SPD_ANG";
}
@Override
public void onTouchEvent(MotionEvent event) {
int action = event.getActionMasked();
if (action == MotionEvent.ACTION_DOWN) {
strokeMap.clear();
}
for (int i = 0; i < event.getPointerCount(); i++) {
Stroke stroke = classifierData.getStroke(event.getPointerId(i));
if (strokeMap.get(stroke) == null) {
strokeMap.put(stroke, new Data());
}
if (action != MotionEvent.ACTION_UP
&& action != MotionEvent.ACTION_CANCEL
&& !(action == MotionEvent.ACTION_POINTER_UP && i == event.getActionIndex())) {
strokeMap.get(stroke).addPoint(stroke.getPoints().get(stroke.getPoints().size() - 1));
}
}
}
@Override
public float getFalseTouchEvaluation(Stroke stroke) {
Data data = strokeMap.get(stroke);
return SpeedVarianceEvaluator.evaluate(data.getAnglesVariance())
+ SpeedAnglesPercentageEvaluator.evaluate(data.getAnglesPercentage());
}
private static class Data {
private static final float DURATION_SCALE = 1e8f;
private static final float LENGTH_SCALE = 1.0f;
private static final float ANGLE_DEVIATION = (float) Math.PI / 10.0f;
private List<Point> lastThreePoints = new ArrayList<>();
private Point previousPoint;
private float previousAngle;
private float sumSquares;
private float sum;
private float count;
private float dist;
private float anglesCount;
private float acceleratingAngles;
public Data() {
previousPoint = null;
previousAngle = (float) Math.PI;
sumSquares = 0.0f;
sum = 0.0f;
count = 1.0f;
dist = 0.0f;
anglesCount = acceleratingAngles = 0.0f;
}
public void addPoint(Point point) {
if (previousPoint != null) {
dist += previousPoint.dist(point);
}
previousPoint = point;
Point speedPoint =
new Point((float) point.timeOffsetNano / DURATION_SCALE, dist / LENGTH_SCALE);
// Checking if the added point is different than the previously added point
// Repetitions are being ignored so that proper angles are calculated.
if (lastThreePoints.isEmpty()
|| !lastThreePoints.get(lastThreePoints.size() - 1).equals(speedPoint)) {
lastThreePoints.add(speedPoint);
if (lastThreePoints.size() == 4) {
lastThreePoints.remove(0);
float angle =
lastThreePoints.get(1).getAngle(lastThreePoints.get(0), lastThreePoints.get(2));
anglesCount++;
if (angle >= (float) Math.PI - ANGLE_DEVIATION) {
acceleratingAngles++;
}
float difference = angle - previousAngle;
sum += difference;
sumSquares += difference * difference;
count += 1.0f;
previousAngle = angle;
}
}
}
public float getAnglesVariance() {
return sumSquares / count - (sum / count) * (sum / count);
}
public float getAnglesPercentage() {
if (anglesCount == 0.0f) {
return 1.0f;
}
return (acceleratingAngles) / anglesCount;
}
}
}
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