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/*
* 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 {
static final int NUM_PAST = 4;
static final int LONGEST_PAST_TIME = 200;
final float mPastX[] = new float[NUM_PAST];
final float mPastY[] = new float[NUM_PAST];
final long mPastTime[] = new long[NUM_PAST];
float mYVelocity;
float mXVelocity;
public void clear() {
mPastTime[0] = 0;
}
public void addMovement(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
clear();
return;
}
long time = ev.getEventTime();
final int N = ev.getHistorySize();
for (int i=0; i<N; 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) {
int drop = -1;
int i;
final long[] pastTime = mPastTime;
for (i=0; i<NUM_PAST; i++) {
if (pastTime[i] == 0) {
break;
} else if (pastTime[i] < time-LONGEST_PAST_TIME) {
drop = i;
}
}
if (i == NUM_PAST && drop < 0) {
drop = 0;
}
if (drop == i) drop--;
final float[] pastX = mPastX;
final float[] pastY = mPastY;
if (drop >= 0) {
final int start = drop+1;
final int count = NUM_PAST-drop-1;
System.arraycopy(pastX, start, pastX, 0, count);
System.arraycopy(pastY, start, pastY, 0, count);
System.arraycopy(pastTime, start, pastTime, 0, count);
i -= (drop+1);
}
pastX[i] = x;
pastY[i] = y;
pastTime[i] = time;
i++;
if (i < NUM_PAST) {
pastTime[i] = 0;
}
}
public void computeCurrentVelocity(int units) {
computeCurrentVelocity(units, Float.MAX_VALUE);
}
public void computeCurrentVelocity(int units, float maxVelocity) {
final float[] pastX = mPastX;
final float[] pastY = mPastY;
final long[] pastTime = mPastTime;
final float oldestX = pastX[0];
final float oldestY = pastY[0];
final long oldestTime = pastTime[0];
float accumX = 0;
float accumY = 0;
int N=0;
while (N < NUM_PAST) {
if (pastTime[N] == 0) {
break;
}
N++;
}
for (int i=1; i < N; i++) {
final int dur = (int)(pastTime[i] - oldestTime);
if (dur == 0) continue;
float dist = pastX[i] - oldestX;
float vel = (dist/dur) * units; // pixels/frame.
if (accumX == 0) accumX = vel;
else accumX = (accumX + vel) * .5f;
dist = pastY[i] - 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;
}
}
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