1 files changed, 147 insertions, 0 deletions
diff --git a/java/com/android/incallui/answer/impl/classifier/SpeedAnglesClassifier.java b/java/com/android/incallui/answer/impl/classifier/SpeedAnglesClassifier.java
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+++ b/java/com/android/incallui/answer/impl/classifier/SpeedAnglesClassifier.java
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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> mStrokeMap = new ArrayMap<>();
+
+  public SpeedAnglesClassifier(ClassifierData classifierData) {
+    mClassifierData = classifierData;
+  }
+
+  @Override
+  public String getTag() {
+    return "SPD_ANG";
+  }
+
+  @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));
+
+      if (mStrokeMap.get(stroke) == null) {
+        mStrokeMap.put(stroke, new Data());
+      }
+
+      if (action != MotionEvent.ACTION_UP
+          && action != MotionEvent.ACTION_CANCEL
+          && !(action == MotionEvent.ACTION_POINTER_UP && i == event.getActionIndex())) {
+        mStrokeMap.get(stroke).addPoint(stroke.getPoints().get(stroke.getPoints().size() - 1));
+      }
+    }
+  }
+
+  @Override
+  public float getFalseTouchEvaluation(Stroke stroke) {
+    Data data = mStrokeMap.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> mLastThreePoints = new ArrayList<>();
+    private Point mPreviousPoint;
+    private float mPreviousAngle;
+    private float mSumSquares;
+    private float mSum;
+    private float mCount;
+    private float mDist;
+    private float mAnglesCount;
+    private float mAcceleratingAngles;
+
+    public Data() {
+      mPreviousPoint = null;
+      mPreviousAngle = (float) Math.PI;
+      mSumSquares = 0.0f;
+      mSum = 0.0f;
+      mCount = 1.0f;
+      mDist = 0.0f;
+      mAnglesCount = mAcceleratingAngles = 0.0f;
+    }
+
+    public void addPoint(Point point) {
+      if (mPreviousPoint != null) {
+        mDist += mPreviousPoint.dist(point);
+      }
+
+      mPreviousPoint = point;
+      Point speedPoint =
+          new Point((float) point.timeOffsetNano / DURATION_SCALE, mDist / 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 (mLastThreePoints.isEmpty()
+          || !mLastThreePoints.get(mLastThreePoints.size() - 1).equals(speedPoint)) {
+        mLastThreePoints.add(speedPoint);
+        if (mLastThreePoints.size() == 4) {
+          mLastThreePoints.remove(0);
+
+          float angle =
+              mLastThreePoints.get(1).getAngle(mLastThreePoints.get(0), mLastThreePoints.get(2));
+
+          mAnglesCount++;
+          if (angle >= (float) Math.PI - ANGLE_DEVIATION) {
+            mAcceleratingAngles++;
+          }
+
+          float difference = angle - mPreviousAngle;
+          mSum += difference;
+          mSumSquares += difference * difference;
+          mCount += 1.0f;
+          mPreviousAngle = angle;
+        }
+      }
+    }
+
+    public float getAnglesVariance() {
+      return mSumSquares / mCount - (mSum / mCount) * (mSum / mCount);
+    }
+
+    public float getAnglesPercentage() {
+      if (mAnglesCount == 0.0f) {
+        return 1.0f;
+      }
+      return (mAcceleratingAngles) / mAnglesCount;
+    }
+  }
+}