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Merge "Use a circular buffer in VelocityTracker"

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This commit is contained in:
Adam Powell
2010-02-05 13:01:22 -08:00
committed by Android Code Review
parent 7d039fbe07 ce760cd6df
commit b09ef7b4fa
1 changed files with 33 additions and 55 deletions
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88
core/java/android/view/VelocityTracker.java
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@@ -59,6 +59,8 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
final float mPastY[] = new float[NUM_PAST];
final long mPastTime[] = new long[NUM_PAST];
int mLastTouch;
float mYVelocity;
float mXVelocity;
@@ -105,7 +107,10 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
* Reset the velocity tracker back to its initial state.
*/
public void clear() {
mPastTime[0] = 0;
final long[] pastTime = mPastTime;
for (int i = 0; i < NUM_PAST; i++) {
pastTime[i] = 0;
}
}
/**
@@ -128,42 +133,11 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
}
private void addPoint(float x, float y, long time) {
int drop = -1;
int i;
if (localLOGV) Log.v(TAG, "Adding past y=" + y + " time=" + time);
final long[] pastTime = mPastTime;
for (i=0; i<NUM_PAST; i++) {
if (pastTime[i] == 0) {
break;
} else if (pastTime[i] < time-LONGEST_PAST_TIME) {
if (localLOGV) Log.v(TAG, "Dropping past too old at "
+ i + " time=" + pastTime[i]);
drop = i;
}
}
if (localLOGV) Log.v(TAG, "Add index: " + i);
if (i == NUM_PAST && drop < 0) {
drop = 0;
}
if (drop == i) drop--;
final float[] pastX = mPastX;
final float[] pastY = mPastY;
if (drop >= 0) {
if (localLOGV) Log.v(TAG, "Dropping up to #" + drop);
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;
}
final int lastTouch = (mLastTouch + 1) % NUM_PAST;
mPastX[lastTouch] = x;
mPastY[lastTouch] = y;
mPastTime[lastTouch] = time;
mLastTouch = lastTouch;
}
/**
@@ -193,35 +167,39 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
final float[] pastX = mPastX;
final float[] pastY = mPastY;
final long[] pastTime = mPastTime;
final int lastTouch = mLastTouch;
// find oldest acceptable time
int oldestTouch = lastTouch;
if (pastTime[lastTouch] > 0) { // cleared ?
oldestTouch = (lastTouch + 1) % NUM_PAST;
final float acceptableTime = pastTime[lastTouch] - LONGEST_PAST_TIME;
while (pastTime[oldestTouch] < acceptableTime) {
oldestTouch = (oldestTouch + 1) % NUM_PAST;
}
}
// Kind-of stupid.
final float oldestX = pastX[0];
final float oldestY = pastY[0];
final long oldestTime = pastTime[0];
final float oldestX = pastX[oldestTouch];
final float oldestY = pastY[oldestTouch];
final long oldestTime = pastTime[oldestTouch];
float accumX = 0;
float accumY = 0;
int N=0;
while (N < NUM_PAST) {
if (pastTime[N] == 0) {
break;
}
N++;
}
float N = (lastTouch - oldestTouch + NUM_PAST) % NUM_PAST + 1;
// Skip the last received event, since it is probably pretty noisy.
if (N > 3) N--;
for (int i=1; i < N; i++) {
final int dur = (int)(pastTime[i] - oldestTime);
final int j = (oldestTouch + i) % NUM_PAST;
final int dur = (int)(pastTime[j] - oldestTime);
if (dur == 0) continue;
float dist = pastX[i] - oldestX;
float dist = pastX[j] - oldestX;
float vel = (dist/dur) * units; // pixels/frame.
if (accumX == 0) accumX = vel;
else accumX = (accumX + vel) * .5f;
accumX = (accumX == 0) ? vel : (accumX + vel) * .5f;
dist = pastY[i] - oldestY;
dist = pastY[j] - oldestY;
vel = (dist/dur) * units; // pixels/frame.
if (accumY == 0) accumY = vel;
else accumY = (accumY + vel) * .5f;
accumY = (accumY == 0) ? vel : (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);