Added in API level 1

Summary: Ctors | Methods | Inherited Methods

Scroller

Kotlin |Java

public class Scroller
extends Object

java.lang.Object
↳	android.widget.Scroller

This class encapsulates scrolling. You can use scrollers (Scroller or OverScroller) to collect the data you need to produce a scrolling animation—for example, in response to a fling gesture. Scrollers track scroll offsets for you over time, but they don't automatically apply those positions to your view. It's your responsibility to get and apply new coordinates at a rate that will make the scrolling animation look smooth.

Here is a simple example:

 private Scroller mScroller = new Scroller(context);
 ...
 public void zoomIn() {
     // Revert any animation currently in progress
     mScroller.forceFinished(true);
     // Start scrolling by providing a starting point and
     // the distance to travel
     mScroller.startScroll(0, 0, 100, 0);
     // Invalidate to request a redraw
     invalidate();
 }

To track the changing positions of the x/y coordinates, use computeScrollOffset(). The method returns a boolean to indicate whether the scroller is finished. If it isn't, it means that a fling or programmatic pan operation is still in progress. You can use this method to find the current offsets of the x and y coordinates, for example:

if (mScroller.computeScrollOffset()) {
     // Get current x and y positions
     int currX = mScroller.getCurrX();
     int currY = mScroller.getCurrY();
    ...
 }

Summary

Public constructors
`Scroller(Context context)` Create a Scroller with the default duration and interpolator.
`Scroller(Context context, Interpolator interpolator)` Create a Scroller with the specified interpolator.
`Scroller(Context context, Interpolator interpolator, boolean flywheel)` Create a Scroller with the specified interpolator.

Public methods
`void`	`abortAnimation()` Stops the animation.
`boolean`	`computeScrollOffset()` Call this when you want to know the new location.
`void`	`extendDuration(int extend)` Extend the scroll animation.
`void`	`fling(int startX, int startY, int velocityX, int velocityY, int minX, int maxX, int minY, int maxY)` Start scrolling based on a fling gesture.
`final void`	`forceFinished(boolean finished)` Force the finished field to a particular value.
`float`	`getCurrVelocity()` Returns the current velocity.
`final int`	`getCurrX()` Returns the current X offset in the scroll.
`final int`	`getCurrY()` Returns the current Y offset in the scroll.
`final int`	`getDuration()` Returns how long the scroll event will take, in milliseconds.
`final int`	`getFinalX()` Returns where the scroll will end.
`final int`	`getFinalY()` Returns where the scroll will end.
`final int`	`getStartX()` Returns the start X offset in the scroll.
`final int`	`getStartY()` Returns the start Y offset in the scroll.
`final boolean`	`isFinished()` Returns whether the scroller has finished scrolling.
`void`	`setFinalX(int newX)` Sets the final position (X) for this scroller.
`void`	`setFinalY(int newY)` Sets the final position (Y) for this scroller.
`final void`	`setFriction(float friction)` The amount of friction applied to flings.
`void`	`startScroll(int startX, int startY, int dx, int dy, int duration)` Start scrolling by providing a starting point, the distance to travel, and the duration of the scroll.
`void`	`startScroll(int startX, int startY, int dx, int dy)` Start scrolling by providing a starting point and the distance to travel.
`int`	`timePassed()` Returns the time elapsed since the beginning of the scrolling.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public constructors

Scroller

Added in API level 1

public Scroller (Context context)

Create a Scroller with the default duration and interpolator.

Parameters
`context`	`Context`

Scroller

Added in API level 1

public Scroller (Context context, 
                Interpolator interpolator)

Create a Scroller with the specified interpolator. If the interpolator is null, the default (viscous) interpolator will be used. "Flywheel" behavior will be in effect for apps targeting Honeycomb or newer.

Parameters
`context`	`Context`
`interpolator`	`Interpolator`

Scroller

Added in API level 11

public Scroller (Context context, 
                Interpolator interpolator, 
                boolean flywheel)

Create a Scroller with the specified interpolator. If the interpolator is null, the default (viscous) interpolator will be used. Specify whether or not to support progressive "flywheel" behavior in flinging.

Parameters
`context`	`Context`
`interpolator`	`Interpolator`
`flywheel`	`boolean`

Public methods

abortAnimation

Added in API level 1

public void abortAnimation ()

Stops the animation. Contrary to forceFinished(boolean), aborting the animating cause the scroller to move to the final x and y position

See also:

forceFinished(boolean)

computeScrollOffset

Added in API level 1

public boolean computeScrollOffset ()

Call this when you want to know the new location. If it returns true, the animation is not yet finished.

Returns
`boolean`

extendDuration

Added in API level 1

public void extendDuration (int extend)

Extend the scroll animation. This allows a running animation to scroll further and longer, when used with setFinalX(int) or setFinalY(int).

Parameters
`extend`	`int`: Additional time to scroll in milliseconds.

See also:

setFinalX(int)
setFinalY(int)

fling

Added in API level 1

public void fling (int startX, 
                int startY, 
                int velocityX, 
                int velocityY, 
                int minX, 
                int maxX, 
                int minY, 
                int maxY)

Start scrolling based on a fling gesture. The distance travelled will depend on the initial velocity of the fling.

Parameters
`startX`	`int`: Starting point of the scroll (X)
`startY`	`int`: Starting point of the scroll (Y)
`velocityX`	`int`: Initial velocity of the fling (X) measured in pixels per second.
`velocityY`	`int`: Initial velocity of the fling (Y) measured in pixels per second
`minX`	`int`: Minimum X value. The scroller will not scroll past this point.
`maxX`	`int`: Maximum X value. The scroller will not scroll past this point.
`minY`	`int`: Minimum Y value. The scroller will not scroll past this point.
`maxY`	`int`: Maximum Y value. The scroller will not scroll past this point.

forceFinished

Added in API level 1

public final void forceFinished (boolean finished)

Force the finished field to a particular value.

Parameters
`finished`	`boolean`: The new finished value.

getCurrVelocity

Added in API level 14

public float getCurrVelocity ()

Returns the current velocity.

Returns
`float`	The original velocity less the deceleration. Result may be negative.

getCurrX

Added in API level 1

public final int getCurrX ()

Returns the current X offset in the scroll.

Returns
`int`	The new X offset as an absolute distance from the origin.

getCurrY

Added in API level 1

public final int getCurrY ()

Returns the current Y offset in the scroll.

Returns
`int`	The new Y offset as an absolute distance from the origin.

getDuration

Added in API level 1

public final int getDuration ()

Returns how long the scroll event will take, in milliseconds.

Returns
`int`	The duration of the scroll in milliseconds.

getFinalX

Added in API level 1

public final int getFinalX ()

Returns where the scroll will end. Valid only for "fling" scrolls.

Returns
`int`	The final X offset as an absolute distance from the origin.

getFinalY

Added in API level 1

public final int getFinalY ()

Returns where the scroll will end. Valid only for "fling" scrolls.

Returns
`int`	The final Y offset as an absolute distance from the origin.

getStartX

Added in API level 3

public final int getStartX ()

Returns the start X offset in the scroll.

Returns
`int`	The start X offset as an absolute distance from the origin.

getStartY

Added in API level 3

public final int getStartY ()

Returns the start Y offset in the scroll.

Returns
`int`	The start Y offset as an absolute distance from the origin.

isFinished

Added in API level 1

public final boolean isFinished ()

Returns whether the scroller has finished scrolling.

Returns
`boolean`	True if the scroller has finished scrolling, false otherwise.

setFinalX

Added in API level 1

public void setFinalX (int newX)

Sets the final position (X) for this scroller.

Parameters
`newX`	`int`: The new X offset as an absolute distance from the origin.

See also:

setFinalY

Added in API level 1

public void setFinalY (int newY)

Sets the final position (Y) for this scroller.

Parameters
`newY`	`int`: The new Y offset as an absolute distance from the origin.

See also:

setFriction

Added in API level 11

public final void setFriction (float friction)

The amount of friction applied to flings. The default value is ViewConfiguration#getScrollFriction.

Parameters
`friction`	`float`: A scalar dimension-less value representing the coefficient of friction.

startScroll

Added in API level 1

public void startScroll (int startX, 
                int startY, 
                int dx, 
                int dy, 
                int duration)

Start scrolling by providing a starting point, the distance to travel, and the duration of the scroll.

Parameters
`startX`	`int`: Starting horizontal scroll offset in pixels. Positive numbers will scroll the content to the left.
`startY`	`int`: Starting vertical scroll offset in pixels. Positive numbers will scroll the content up.
`dx`	`int`: Horizontal distance to travel. Positive numbers will scroll the content to the left.
`dy`	`int`: Vertical distance to travel. Positive numbers will scroll the content up.
`duration`	`int`: Duration of the scroll in milliseconds.

startScroll

Added in API level 1

public void startScroll (int startX, 
                int startY, 
                int dx, 
                int dy)

Start scrolling by providing a starting point and the distance to travel. The scroll will use the default value of 250 milliseconds for the duration.

Parameters
`startX`	`int`: Starting horizontal scroll offset in pixels. Positive numbers will scroll the content to the left.
`startY`	`int`: Starting vertical scroll offset in pixels. Positive numbers will scroll the content up.
`dx`	`int`: Horizontal distance to travel. Positive numbers will scroll the content to the left.
`dy`	`int`: Vertical distance to travel. Positive numbers will scroll the content up.

timePassed

Added in API level 1

public int timePassed ()

Returns the time elapsed since the beginning of the scrolling.

Returns
`int`	The elapsed time in milliseconds.