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Diffstat (limited to 'java/src/com/android/inputmethod/latin/SwipeTracker.java')
| -rw-r--r-- | java/src/com/android/inputmethod/latin/SwipeTracker.java | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/java/src/com/android/inputmethod/latin/SwipeTracker.java b/java/src/com/android/inputmethod/latin/SwipeTracker.java new file mode 100644 index 000000000..970e91965 --- /dev/null +++ b/java/src/com/android/inputmethod/latin/SwipeTracker.java @@ -0,0 +1,157 @@ +/* + * Copyright (C) 2010 Google Inc. + * + * 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.inputmethod.latin; + +import android.view.MotionEvent; + +class SwipeTracker { + private static final int NUM_PAST = 4; + private static final int LONGEST_PAST_TIME = 200; + + final EventRingBuffer mBuffer = new EventRingBuffer(NUM_PAST); + + private float mYVelocity; + private float mXVelocity; + + public void addMovement(MotionEvent ev) { + if (ev.getAction() == MotionEvent.ACTION_DOWN) { + mBuffer.clear(); + return; + } + long time = ev.getEventTime(); + final int count = ev.getHistorySize(); + for (int i = 0; i < count; i++) { + addPoint(ev.getHistoricalX(i), ev.getHistoricalY(i), ev.getHistoricalEventTime(i)); + } + addPoint(ev.getX(), ev.getY(), time); + } + + private void addPoint(float x, float y, long time) { + final EventRingBuffer buffer = mBuffer; + while (buffer.size() > 0) { + long lastT = buffer.getTime(0); + if (lastT >= time - LONGEST_PAST_TIME) + break; + buffer.dropOldest(); + } + buffer.add(x, y, time); + } + + public void computeCurrentVelocity(int units) { + computeCurrentVelocity(units, Float.MAX_VALUE); + } + + public void computeCurrentVelocity(int units, float maxVelocity) { + final EventRingBuffer buffer = mBuffer; + final float oldestX = buffer.getX(0); + final float oldestY = buffer.getY(0); + final long oldestTime = buffer.getTime(0); + + float accumX = 0; + float accumY = 0; + final int count = buffer.size(); + for (int pos = 1; pos < count; pos++) { + final int dur = (int)(buffer.getTime(pos) - oldestTime); + if (dur == 0) continue; + float dist = buffer.getX(pos) - oldestX; + float vel = (dist / dur) * units; // pixels/frame. + if (accumX == 0) accumX = vel; + else accumX = (accumX + vel) * .5f; + + dist = buffer.getY(pos) - oldestY; + vel = (dist / dur) * units; // pixels/frame. + if (accumY == 0) accumY = vel; + else accumY = (accumY + vel) * .5f; + } + mXVelocity = accumX < 0.0f ? Math.max(accumX, -maxVelocity) + : Math.min(accumX, maxVelocity); + mYVelocity = accumY < 0.0f ? Math.max(accumY, -maxVelocity) + : Math.min(accumY, maxVelocity); + } + + public float getXVelocity() { + return mXVelocity; + } + + public float getYVelocity() { + return mYVelocity; + } + + static class EventRingBuffer { + private final int bufSize; + private final float xBuf[]; + private final float yBuf[]; + private final long timeBuf[]; + private int top; // points new event + private int end; // points oldest event + private int count; // the number of valid data + + public EventRingBuffer(int max) { + this.bufSize = max; + xBuf = new float[max]; + yBuf = new float[max]; + timeBuf = new long[max]; + clear(); + } + + public void clear() { + top = end = count = 0; + } + + public int size() { + return count; + } + + // Position 0 points oldest event + private int index(int pos) { + return (end + pos) % bufSize; + } + + private int advance(int index) { + return (index + 1) % bufSize; + } + + public void add(float x, float y, long time) { + xBuf[top] = x; + yBuf[top] = y; + timeBuf[top] = time; + top = advance(top); + if (count < bufSize) { + count++; + } else { + end = advance(end); + } + } + + public float getX(int pos) { + return xBuf[index(pos)]; + } + + public float getY(int pos) { + return yBuf[index(pos)]; + } + + public long getTime(int pos) { + return timeBuf[index(pos)]; + } + + public void dropOldest() { + count--; + end = advance(end); + } + } +}
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