1 files changed, 99 insertions, 0 deletions
diff --git a/java/com/android/incallui/answer/impl/classifier/AccelerationClassifier.java b/java/com/android/incallui/answer/impl/classifier/AccelerationClassifier.java
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+++ b/java/com/android/incallui/answer/impl/classifier/AccelerationClassifier.java
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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;
+    }
+  }
+}