File	Doc	Category	Size	Date	Package
VelocityTracker.java	API Doc	Android 5.1 API	10692	Thu Mar 12 22:22:10 GMT 2015	android.view

VelocityTracker

• java.lang.Object

Fields Summary
private static final android.util.Pools.SynchronizedPool	sPool
private static final int	ACTIVE_POINTER_ID
private long	mPtr
private final String	mStrategy

Constructors Summary
private VelocityTracker(String strategy) mPtr = nativeInitialize(strategy); mStrategy = strategy;

Methods Summary
public void	addMovement(MotionEvent event) Add a user's movement to the tracker. You should call this for the initial {@link MotionEvent#ACTION_DOWN}, the following {@link MotionEvent#ACTION_MOVE} events that you receive, and the final {@link MotionEvent#ACTION_UP}. You can, however, call this for whichever events you desire. param event The MotionEvent you received and would like to track. if (event == null) { throw new IllegalArgumentException("event must not be null"); } nativeAddMovement(mPtr, event);
public void	clear() Reset the velocity tracker back to its initial state. nativeClear(mPtr);
public void	computeCurrentVelocity(int units) Equivalent to invoking {@link #computeCurrentVelocity(int, float)} with a maximum velocity of Float.MAX_VALUE. see #computeCurrentVelocity(int, float) nativeComputeCurrentVelocity(mPtr, units, Float.MAX_VALUE);
public void	computeCurrentVelocity(int units, float maxVelocity) Compute the current velocity based on the points that have been collected. Only call this when you actually want to retrieve velocity information, as it is relatively expensive. You can then retrieve the velocity with {@link #getXVelocity()} and {@link #getYVelocity()}. param units The units you would like the velocity in. A value of 1 provides pixels per millisecond, 1000 provides pixels per second, etc. param maxVelocity The maximum velocity that can be computed by this method. This value must be declared in the same unit as the units parameter. This value must be positive. nativeComputeCurrentVelocity(mPtr, units, maxVelocity);
protected void	finalize() try { if (mPtr != 0) { nativeDispose(mPtr); mPtr = 0; } } finally { super.finalize(); }
public boolean	getEstimator(int id, android.view.VelocityTracker$Estimator outEstimator) Get an estimator for the movements of a pointer using past movements of the pointer to predict future movements. It is not necessary to call {@link #computeCurrentVelocity(int)} before calling this method. param id Which pointer's velocity to return. param outEstimator The estimator to populate. return True if an estimator was obtained, false if there is no information available about the pointer. hide For internal use only. Not a final API. if (outEstimator == null) { throw new IllegalArgumentException("outEstimator must not be null"); } return nativeGetEstimator(mPtr, id, outEstimator);
public float	getXVelocity() Retrieve the last computed X velocity. You must first call {@link #computeCurrentVelocity(int)} before calling this function. return The previously computed X velocity. return nativeGetXVelocity(mPtr, ACTIVE_POINTER_ID);
public float	getXVelocity(int id) Retrieve the last computed X velocity. You must first call {@link #computeCurrentVelocity(int)} before calling this function. param id Which pointer's velocity to return. return The previously computed X velocity. return nativeGetXVelocity(mPtr, id);
public float	getYVelocity() Retrieve the last computed Y velocity. You must first call {@link #computeCurrentVelocity(int)} before calling this function. return The previously computed Y velocity. return nativeGetYVelocity(mPtr, ACTIVE_POINTER_ID);
public float	getYVelocity(int id) Retrieve the last computed Y velocity. You must first call {@link #computeCurrentVelocity(int)} before calling this function. param id Which pointer's velocity to return. return The previously computed Y velocity. return nativeGetYVelocity(mPtr, id);
private static native void	nativeAddMovement(long ptr, MotionEvent event)
private static native void	nativeClear(long ptr)
private static native void	nativeComputeCurrentVelocity(long ptr, int units, float maxVelocity)
private static native void	nativeDispose(long ptr)
private static native boolean	nativeGetEstimator(long ptr, int id, android.view.VelocityTracker$Estimator outEstimator)
private static native float	nativeGetXVelocity(long ptr, int id)
private static native float	nativeGetYVelocity(long ptr, int id)
private static native long	nativeInitialize(java.lang.String strategy)
public static android.view.VelocityTracker	obtain(java.lang.String strategy) Obtains a velocity tracker with the specified strategy. For testing and comparison purposes only. param strategy The strategy, or null to use the default. return The velocity tracker. hide if (strategy == null) { return obtain(); } return new VelocityTracker(strategy);
public static android.view.VelocityTracker	obtain() Retrieve a new VelocityTracker object to watch the velocity of a motion. Be sure to call {@link #recycle} when done. You should generally only maintain an active object while tracking a movement, so that the VelocityTracker can be re-used elsewhere. return Returns a new VelocityTracker. VelocityTracker instance = sPool.acquire(); return (instance != null) ? instance : new VelocityTracker(null);
public void	recycle() Return a VelocityTracker object back to be re-used by others. You must not touch the object after calling this function. if (mStrategy == null) { clear(); sPool.release(this); }