| /* |
| * 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.systemui.classifier; |
| |
| import android.os.SystemClock; |
| |
| import java.util.ArrayList; |
| |
| /** |
| * Holds the evaluations for ended strokes and gestures. These values are decreased through time. |
| */ |
| public class HistoryEvaluator { |
| private static final float INTERVAL = 50.0f; |
| private static final float HISTORY_FACTOR = 0.9f; |
| private static final float EPSILON = 1e-5f; |
| |
| private final ArrayList<Data> mStrokes = new ArrayList<>(); |
| private final ArrayList<Data> mGestureWeights = new ArrayList<>(); |
| private long mLastUpdate; |
| |
| public HistoryEvaluator() { |
| mLastUpdate = SystemClock.elapsedRealtime(); |
| } |
| |
| public void addStroke(float evaluation) { |
| decayValue(); |
| mStrokes.add(new Data(evaluation)); |
| } |
| |
| public void addGesture(float evaluation) { |
| decayValue(); |
| mGestureWeights.add(new Data(evaluation)); |
| } |
| |
| /** |
| * Calculates the weighted average of strokes and adds to it the weighted average of gestures |
| */ |
| public float getEvaluation() { |
| return weightedAverage(mStrokes) + weightedAverage(mGestureWeights); |
| } |
| |
| private float weightedAverage(ArrayList<Data> list) { |
| float sumValue = 0.0f; |
| float sumWeight = 0.0f; |
| int size = list.size(); |
| for (int i = 0; i < size; i++) { |
| Data data = list.get(i); |
| sumValue += data.evaluation * data.weight; |
| sumWeight += data.weight; |
| } |
| |
| if (sumWeight == 0.0f) { |
| return 0.0f; |
| } |
| |
| return sumValue / sumWeight; |
| } |
| |
| private void decayValue() { |
| long time = SystemClock.elapsedRealtime(); |
| |
| if (time <= mLastUpdate) { |
| return; |
| } |
| |
| // All weights are multiplied by HISTORY_FACTOR after each INTERVAL milliseconds. |
| float factor = (float) Math.pow(HISTORY_FACTOR, (time - mLastUpdate) / INTERVAL); |
| |
| decayValue(mStrokes, factor); |
| decayValue(mGestureWeights, factor); |
| mLastUpdate = time; |
| } |
| |
| private void decayValue(ArrayList<Data> list, float factor) { |
| int size = list.size(); |
| for (int i = 0; i < size; i++) { |
| list.get(i).weight *= factor; |
| } |
| |
| // Removing evaluations with such small weights that they do not matter anymore |
| while (!list.isEmpty() && isZero(list.get(0).weight)) { |
| list.remove(0); |
| } |
| } |
| |
| private boolean isZero(float x) { |
| return x <= EPSILON && x >= -EPSILON; |
| } |
| |
| /** |
| * For each stroke it holds its initial value and the current weight. Initially the |
| * weight is set to 1.0 |
| */ |
| private static class Data { |
| public float evaluation; |
| public float weight; |
| |
| public Data(float evaluation) { |
| this.evaluation = evaluation; |
| weight = 1.0f; |
| } |
| } |
| } |