/** applies the next step in the pan-zoom animation, if any */
private void stepPanZoomAnimation() {
if (zoomPanAnimationEndTime == 0) return;
long now = System.currentTimeMillis();
if (now >= zoomPanAnimationEndTime) {
zoom = zoomTo;
drawOffset.x = panTo.x;
drawOffset.y = panTo.y;
stopPanZoomAnimation();
} else {
long duration = zoomPanAnimationEndTime - zoomPanAnimationStartTime;
long diff = zoomPanAnimationEndTime - now;
float alpha = (float) Math.pow(diff / (float) duration, zoomPanAnimationInterpolationPower);
float beta = 1.0f - alpha;
zoom = (zoomFrom * alpha) + (zoomTo * beta);
drawOffset.x = (int) ((panFrom.x * alpha) + (panTo.x * beta));
drawOffset.y = (int) ((panFrom.y * alpha) + (panTo.y * beta));
}
}
/** pan down by the standard amount */
public void panDown() {
drawOffset.y += getHeight() / (DEFAULT_PAN_DIVISOR * zoom);
}
/** pan up by the standard amount */
public void panUp() {
drawOffset.y -= getHeight() / (DEFAULT_PAN_DIVISOR * zoom);
}
/** set the aggregate y-axis pan */
public void setPanY(int y) {
drawOffset.y = y;
}