/**
* Start scrolling based on a fling gesture. The distance traveled will depend on the initial
* velocity of the fling.
*
* @param startX Starting point of the scroll (X)
* @param startY Starting point of the scroll (Y)
* @param velocityX Initial velocity of the fling (X) measured in pixels per second.
* @param velocityY Initial velocity of the fling (Y) measured in pixels per second
* @param minX Minimum X value. The scroller will not scroll past this point unless overX > 0. If
* overfling is allowed, it will use minX as a springback boundary.
* @param maxX Maximum X value. The scroller will not scroll past this point unless overX > 0. If
* overfling is allowed, it will use maxX as a springback boundary.
* @param minY Minimum Y value. The scroller will not scroll past this point unless overY > 0. If
* overfling is allowed, it will use minY as a springback boundary.
* @param maxY Maximum Y value. The scroller will not scroll past this point unless overY > 0. If
* overfling is allowed, it will use maxY as a springback boundary.
* @param overX Overfling range. If > 0, horizontal overfling in either direction will be
* possible.
* @param overY Overfling range. If > 0, vertical overfling in either direction will be possible.
*/
public void fling(
int startX,
int startY,
int velocityX,
int velocityY,
int minX,
int maxX,
int minY,
int maxY,
int overX,
int overY) {
// Continue a scroll or fling in progress
if (mFlywheel && !isFinished()) {
float oldVelocityX = mScrollerX.mCurrVelocity;
float oldVelocityY = mScrollerY.mCurrVelocity;
if (Math.signum(velocityX) == Math.signum(oldVelocityX)
&& Math.signum(velocityY) == Math.signum(oldVelocityY)) {
velocityX += oldVelocityX;
velocityY += oldVelocityY;
}
}
mMode = FLING_MODE;
mScrollerX.fling(startX, velocityX, minX, maxX, overX);
mScrollerY.fling(startY, velocityY, minY, maxY, overY);
}
/**
* Call this when you want to 'spring back' into a valid coordinate range.
*
* @param startX Starting X coordinate
* @param startY Starting Y coordinate
* @param minX Minimum valid X value
* @param maxX Maximum valid X value
* @param minY Minimum valid Y value
* @param maxY Minimum valid Y value
* @return true if a springback was initiated, false if startX and startY were already within the
* valid range.
*/
public boolean springBack(int startX, int startY, int minX, int maxX, int minY, int maxY) {
mMode = FLING_MODE;
// Make sure both methods are called.
final boolean spingbackX = mScrollerX.springback(startX, minX, maxX);
final boolean spingbackY = mScrollerY.springback(startY, minY, maxY);
return spingbackX || spingbackY;
}
/**
* Call this when you want to know the new location. If it returns true, the animation is not yet
* finished.
*/
public boolean computeScrollOffset() {
if (isFinished()) {
return false;
}
switch (mMode) {
case SCROLL_MODE:
long time = AnimationUtils.currentAnimationTimeMillis();
// Any scroller can be used for time, since they were started
// together in scroll mode. We use X here.
final long elapsedTime = time - mScrollerX.mStartTime;
final int duration = mScrollerX.mDuration;
if (elapsedTime < duration) {
final float q = mInterpolator.getInterpolation(elapsedTime / (float) duration);
mScrollerX.updateScroll(q);
mScrollerY.updateScroll(q);
} else {
abortAnimation();
}
break;
case FLING_MODE:
if (!mScrollerX.mFinished) {
if (!mScrollerX.update()) {
if (!mScrollerX.continueWhenFinished()) {
mScrollerX.finish();
}
}
}
if (!mScrollerY.mFinished) {
if (!mScrollerY.update()) {
if (!mScrollerY.continueWhenFinished()) {
mScrollerY.finish();
}
}
}
break;
}
return true;
}
/**
* Stops the animation. Contrary to {@link #forceFinished(boolean)}, aborting the animating causes
* the scroller to move to the final x and y positions.
*
* @see #forceFinished(boolean)
*/
public void abortAnimation() {
mScrollerX.finish();
mScrollerY.finish();
}
/**
* Notify the scroller that we've reached a vertical boundary. Normally the information to handle
* this will already be known when the animation is started, such as in a call to one of the fling
* functions. However there are cases where this cannot be known in advance. This function will
* animate a parabolic motion from startY to finalY.
*
* @param startY Starting/current Y position
* @param finalY Desired final Y position
* @param overY Magnitude of overscroll allowed. This should be the maximum desired distance from
* finalY. Absolute value - must be positive.
*/
public void notifyVerticalEdgeReached(int startY, int finalY, int overY) {
mScrollerY.notifyEdgeReached(startY, finalY, overY);
}
/**
* Notify the scroller that we've reached a horizontal boundary. Normally the information to
* handle this will already be known when the animation is started, such as in a call to one of
* the fling functions. However there are cases where this cannot be known in advance. This
* function will transition the current motion and animate from startX to finalX as appropriate.
*
* @param startX Starting/current X position
* @param finalX Desired final X position
* @param overX Magnitude of overscroll allowed. This should be the maximum desired distance from
* finalX. Absolute value - must be positive.
*/
public void notifyHorizontalEdgeReached(int startX, int finalX, int overX) {
mScrollerX.notifyEdgeReached(startX, finalX, overX);
}
/**
* Start scrolling by providing a starting point and the distance to travel.
*
* @param startX Starting horizontal scroll offset in pixels. Positive numbers will scroll the
* content to the left.
* @param startY Starting vertical scroll offset in pixels. Positive numbers will scroll the
* content up.
* @param dx Horizontal distance to travel. Positive numbers will scroll the content to the left.
* @param dy Vertical distance to travel. Positive numbers will scroll the content up.
* @param duration Duration of the scroll in milliseconds.
*/
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
mMode = SCROLL_MODE;
mScrollerX.startScroll(startX, dx, duration);
mScrollerY.startScroll(startY, dy, duration);
}
/**
* Sets the final position (Y) for this scroller.
*
* @param newY The new Y offset as an absolute distance from the origin.
* @see #extendDuration(int)
* @see #setFinalX(int)
* @hide Pending removal once nothing depends on it
* @deprecated OverScroller's final position may change during an animation. Instead of setting a
* new final position and extending the duration of an existing scroll, use startScroll to
* begin a new animation.
*/
@Deprecated
public void setFinalY(int newY) {
mScrollerY.setFinalPosition(newY);
}
/**
* Sets the final position (X) for this scroller.
*
* @param newX The new X offset as an absolute distance from the origin.
* @see #extendDuration(int)
* @see #setFinalY(int)
* @hide Pending removal once nothing depends on it
* @deprecated OverScroller's final position may change during an animation. Instead of setting a
* new final position and extending the duration of an existing scroll, use startScroll to
* begin a new animation.
*/
@Deprecated
public void setFinalX(int newX) {
mScrollerX.setFinalPosition(newX);
}
/**
* Extend the scroll animation. This allows a running animation to scroll further and longer, when
* used with {@link #setFinalX(int)} or {@link #setFinalY(int)}.
*
* @param extend Additional time to scroll in milliseconds.
* @see #setFinalX(int)
* @see #setFinalY(int)
* @hide Pending removal once nothing depends on it
* @deprecated OverScrollers don't necessarily have a fixed duration. Instead of setting a new
* final position and extending the duration of an existing scroll, use startScroll to begin a
* new animation.
*/
@Deprecated
public void extendDuration(int extend) {
mScrollerX.extendDuration(extend);
mScrollerY.extendDuration(extend);
}
/**
* Force the finished field to a particular value. Contrary to {@link #abortAnimation()}, forcing
* the animation to finished does NOT cause the scroller to move to the final x and y position.
*
* @param finished The new finished value.
*/
public final void forceFinished(boolean finished) {
mScrollerX.mFinished = mScrollerY.mFinished = finished;
}
/**
* The amount of friction applied to flings. The default value is {@link
* ViewConfiguration#getScrollFriction}.
*
* @param friction A scalar dimension-less value representing the coefficient of friction.
*/
public final void setFriction(float friction) {
mScrollerX.setFriction(friction);
mScrollerY.setFriction(friction);
}
