VelocityTracker

addMovement

 public void addMovement (MotionEvent event)

Add a user's movement to the tracker. You should call this for the initial MotionEvent.ACTION_DOWN, the following MotionEvent.ACTION_MOVE events that you receive, and the final MotionEvent.ACTION_UP. You can, however, call this for whichever events you desire.

clear

 public void clear ()

Reset the velocity tracker back to its initial state.

computeCurrentVelocity

 public void computeCurrentVelocity (int units)

Equivalent to invoking computeCurrentVelocity(int, float) with a maximum velocity of Float.MAX_VALUE.

computeCurrentVelocity

 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 getXVelocity() and getYVelocity().

getAxisVelocity

 public float getAxisVelocity (int axis, int id)

Retrieve the last computed velocity for a given motion axis. You must first call computeCurrentVelocity(int) or computeCurrentVelocity(int, float) before calling this function.

In addition to MotionEvent.AXIS_X and MotionEvent.AXIS_Y which have been supported since the introduction of this class, the following axes can be candidates for this method:

• MotionEvent.AXIS_SCROLL: supported starting Build.VERSION_CODES.UPSIDE_DOWN_CAKE

Before accessing velocities of an axis using this method, check that your VelocityTracker instance supports the axis by using isAxisSupported(int).

getAxisVelocity

 public float getAxisVelocity (int axis)

Equivalent to calling getAxisVelocity(int, int) for axis and the active pointer.

getXVelocity

 public float getXVelocity (int id)

Retrieve the last computed X velocity. You must first call computeCurrentVelocity(int) before calling this function.

getXVelocity

 public float getXVelocity ()

Retrieve the last computed X velocity. You must first call computeCurrentVelocity(int) before calling this function.

getYVelocity

 public float getYVelocity ()

Retrieve the last computed Y velocity. You must first call computeCurrentVelocity(int) before calling this function.

getYVelocity

 public float getYVelocity (int id)

Retrieve the last computed Y velocity. You must first call computeCurrentVelocity(int) before calling this function.

isAxisSupported

 public boolean isAxisSupported (int axis)

Checks whether a given velocity-trackable MotionEvent axis is supported for velocity tracking by this VelocityTracker instance (refer to getAxisVelocity(int, int) for a list of potentially velocity-trackable axes).

Note that the value returned from this method will stay the same for a given instance, so a single check for axis support is enough per a VelocityTracker instance.

obtain

 public static VelocityTracker obtain ()

Retrieve a new VelocityTracker object to watch the velocity of a motion. Be sure to call recycle() when done. You should generally only maintain an active object while tracking a movement, so that the VelocityTracker can be re-used elsewhere.

recycle

 public void recycle ()

Return a VelocityTracker object back to be re-used by others. You must not touch the object after calling this function.

finalize

 protected void finalize ()

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. A subclass overrides the finalize method to dispose of system resources or to perform other cleanup.

The general contract of finalize is that it is invoked if and when the Java virtual machine has determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, except as a result of an action taken by the finalization of some other object or class which is ready to be finalized. The finalize method may take any action, including making this object available again to other threads; the usual purpose of finalize, however, is to perform cleanup actions before the object is irrevocably discarded. For example, the finalize method for an object that represents an input/output connection might perform explicit I/O transactions to break the connection before the object is permanently discarded.

The finalize method of class Object performs no special action; it simply returns normally. Subclasses of Object may override this definition.

The Java programming language does not guarantee which thread will invoke the finalize method for any given object. It is guaranteed, however, that the thread that invokes finalize will not be holding any user-visible synchronization locks when finalize is invoked. If an uncaught exception is thrown by the finalize method, the exception is ignored and finalization of that object terminates.

After the finalize method has been invoked for an object, no further action is taken until the Java virtual machine has again determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, including possible actions by other objects or classes which are ready to be finalized, at which point the object may be discarded.

The finalize method is never invoked more than once by a Java virtual machine for any given object.

Any exception thrown by the finalize method causes the finalization of this object to be halted, but is otherwise ignored.