added in version 22.1.0
belongs to Maven artifact com.android.support:support-compat:28.0.0-alpha1

Summary: Constants | Ctors | Methods | Inherited Methods | [Expand All]

AutoScrollHelper

public abstract class AutoScrollHelper
extends Object implements View.OnTouchListener

java.lang.Object
↳	android.support.v4.widget.AutoScrollHelper

Known Direct Subclasses

ListViewAutoScrollHelper

AutoScrollHelper is a utility class for adding automatic edge-triggered scrolling to Views.

Note: Implementing classes are responsible for overriding the scrollTargetBy(int, int), canTargetScrollHorizontally(int), and canTargetScrollVertically(int) methods. See ListViewAutoScrollHelper for a ListView -specific implementation.

Activation

Automatic scrolling starts when the user touches within an activation area. By default, activation areas are defined as the top, left, right, and bottom 20% of the host view's total area. Touching within the top activation area scrolls up, left scrolls to the left, and so on.

As the user touches closer to the extreme edge of the activation area, scrolling accelerates up to a maximum velocity. When using the default edge type, EDGE_TYPE_INSIDE_EXTEND, moving outside of the view bounds will scroll at the maximum velocity.

The following activation properties may be configured:

Delay after entering activation area before auto-scrolling begins, see setActivationDelay(int). Default value is getTapTimeout() to avoid conflicting with taps.
Location of activation areas, see setEdgeType(int). Default value is EDGE_TYPE_INSIDE_EXTEND.
Size of activation areas relative to view size, see setRelativeEdges(float, float). Default value is 20% for both vertical and horizontal edges.
Maximum size used to constrain relative size, see setMaximumEdges(float, float). Default value is NO_MAX.

Scrolling

When automatic scrolling is active, the helper will repeatedly call scrollTargetBy(int, int) to apply new scrolling offsets.

The following scrolling properties may be configured:

Acceleration ramp-up duration, see setRampUpDuration(int). Default value is 500 milliseconds.
Acceleration ramp-down duration, see setRampDownDuration(int). Default value is 500 milliseconds.
Target velocity relative to view size, see setRelativeVelocity(float, float). Default value is 100% per second for both vertical and horizontal.
Minimum velocity used to constrain relative velocity, see setMinimumVelocity(float, float). When set, scrolling will accelerate to the larger of either this value or the relative target value. Default value is approximately 5 centimeters or 315 dips per second.
Maximum velocity used to constrain relative velocity, see setMaximumVelocity(float, float). Default value is approximately 25 centimeters or 1575 dips per second.

Summary

Constants
`int`	`EDGE_TYPE_INSIDE` Edge type that specifies an activation area starting at the view bounds and extending inward.
`int`	`EDGE_TYPE_INSIDE_EXTEND` Edge type that specifies an activation area starting at the view bounds and extending inward.
`int`	`EDGE_TYPE_OUTSIDE` Edge type that specifies an activation area starting at the view bounds and extending outward.
`float`	`NO_MAX` Constant passed to `setMaximumEdges(float, float)`, `setMaximumVelocity(float, float)`, or `setMinimumVelocity(float, float)`.
`float`	`NO_MIN` Constant passed to `setMaximumEdges(float, float)`, or `setMaximumVelocity(float, float)`, or `setMinimumVelocity(float, float)`.
`float`	`RELATIVE_UNSPECIFIED` Constant passed to `setRelativeEdges(float, float)` or `setRelativeVelocity(float, float)`.

Public constructors
`AutoScrollHelper(View target)` Creates a new helper for scrolling the specified target view.

Public methods
`abstract boolean`	`canTargetScrollHorizontally(int direction)` Override this method to return whether the target view can be scrolled horizontally in a certain direction.
`abstract boolean`	`canTargetScrollVertically(int direction)` Override this method to return whether the target view can be scrolled vertically in a certain direction.
`boolean`	`isEnabled()`
`boolean`	`isExclusive()` Indicates whether the scroll helper handles touch events exclusively during scrolling.
`boolean`	`onTouch(View v, MotionEvent event)` Handles touch events by activating automatic scrolling, adjusting scroll velocity, or stopping.
`abstract void`	`scrollTargetBy(int deltaX, int deltaY)` Override this method to scroll the target view by the specified number of pixels.
`AutoScrollHelper`	`setActivationDelay(int delayMillis)` Sets the delay after entering an activation edge before activation of auto-scrolling.
`AutoScrollHelper`	`setEdgeType(int type)` Sets the activation edge type, one of: `EDGE_TYPE_INSIDE` for edges that respond to touches inside the bounds of the host view.
`AutoScrollHelper`	`setEnabled(boolean enabled)` Sets whether the scroll helper is enabled and should respond to touch events.
`AutoScrollHelper`	`setExclusive(boolean exclusive)` Enables or disables exclusive handling of touch events during scrolling.
`AutoScrollHelper`	`setMaximumEdges(float horizontalMax, float verticalMax)` Sets the absolute maximum edge size.
`AutoScrollHelper`	`setMaximumVelocity(float horizontalMax, float verticalMax)` Sets the absolute maximum scrolling velocity.
`AutoScrollHelper`	`setMinimumVelocity(float horizontalMin, float verticalMin)` Sets the absolute minimum scrolling velocity.
`AutoScrollHelper`	`setRampDownDuration(int durationMillis)` Sets the amount of time after de-activation of auto-scrolling that is takes to slow to a stop.
`AutoScrollHelper`	`setRampUpDuration(int durationMillis)` Sets the amount of time after activation of auto-scrolling that is takes to reach target velocity for the current touch position.
`AutoScrollHelper`	`setRelativeEdges(float horizontal, float vertical)` Sets the activation edge size relative to the host view's dimensions.
`AutoScrollHelper`	`setRelativeVelocity(float horizontal, float vertical)` Sets the target scrolling velocity relative to the host view's dimensions.

Inherited methods

From class


  
    java.lang.Object

From interface


  
    android.view.View.OnTouchListener

Constants

EDGE_TYPE_INSIDE

added in version 22.1.0

int EDGE_TYPE_INSIDE

Edge type that specifies an activation area starting at the view bounds and extending inward. Moving outside the view bounds will stop scrolling.

See also:

setEdgeType(int)

Constant Value: 0 (0x00000000)

EDGE_TYPE_INSIDE_EXTEND

added in version 22.1.0

int EDGE_TYPE_INSIDE_EXTEND

Edge type that specifies an activation area starting at the view bounds and extending inward. After activation begins, moving outside the view bounds will continue scrolling.

See also:

setEdgeType(int)

Constant Value: 1 (0x00000001)

EDGE_TYPE_OUTSIDE

added in version 22.1.0

int EDGE_TYPE_OUTSIDE

Edge type that specifies an activation area starting at the view bounds and extending outward. Moving inside the view bounds will stop scrolling.

See also:

setEdgeType(int)

Constant Value: 2 (0x00000002)

NO_MAX

added in version 22.1.0

float NO_MAX

Constant passed to setMaximumEdges(float, float), setMaximumVelocity(float, float), or setMinimumVelocity(float, float). Using this value ensures that the computed relative value is always used without constraining to a particular minimum or maximum value.

Constant Value: 3.4028235E38

NO_MIN

added in version 22.1.0

float NO_MIN

Constant passed to setMaximumEdges(float, float), or setMaximumVelocity(float, float), or setMinimumVelocity(float, float). Using this value ensures that the computed relative value is always used without constraining to a particular minimum or maximum value.

Constant Value: 0.0

RELATIVE_UNSPECIFIED

added in version 22.1.0

float RELATIVE_UNSPECIFIED

Constant passed to setRelativeEdges(float, float) or setRelativeVelocity(float, float). Using this value ensures that the computed relative value is ignored and the absolute maximum value is always used.

Constant Value: 0.0

Public constructors