Added in API level 34

BackEvent

class BackEvent
kotlin.Any
   ↳ android.window.BackEvent

Object used to report back gesture progress. Holds information about the touch event, swipe direction and the animation progress that predictive back animations should seek to.

Summary

Constants
static Int

Indicates that the edge swipe starts from the left edge of the screen
static Int

Indicates that the back event was not triggered by an edge swipe back gesture.
static Int

Indicates that the edge swipe starts from the right edge of the screen
Public constructors
BackEvent(touchX: Float, touchY: Float, progress: Float, swipeEdge: Int)

Creates a new BackEvent instance with a frame time of 0.
BackEvent(touchX: Float, touchY: Float, progress: Float, swipeEdge: Int, frameTimeMillis: Long)

Creates a new BackEvent instance.
Public methods
Boolean
equals(other: Any?)
Long

Returns the frameTime of the BackEvent in milliseconds.
Float

Returns a value between 0 and 1 on how far along the back gesture is.
Int

Returns the screen edge that the swipe starts from.
Float

Returns the absolute X location of the touch point, or NaN if the event is from a button press.
Float

Returns the absolute Y location of the touch point, or NaN if the event is from a button press.
String

Constants

EDGE_LEFT

Added in API level 34
static val EDGE_LEFT: Int

Indicates that the edge swipe starts from the left edge of the screen

Value: 0

EDGE_NONE

Added in API level Baklava
static val EDGE_NONE: Int

Indicates that the back event was not triggered by an edge swipe back gesture. This applies to cases like using the back button in 3-button navigation or pressing a hardware back button.

Value: 2

EDGE_RIGHT

Added in API level 34
static val EDGE_RIGHT: Int

Indicates that the edge swipe starts from the right edge of the screen

Value: 1

Public constructors

BackEvent

Added in API level 34
BackEvent(
    touchX: Float, 
    touchY: Float, 
    progress: Float, 
    swipeEdge: Int)

Creates a new BackEvent instance with a frame time of 0.

Parameters
touchX Float: Absolute X location of the touch point of this event.
touchY Float: Absolute Y location of the touch point of this event.
progress Float: Value between 0 and 1 on how far along the back gesture is.
swipeEdge Int: Indicates which edge the swipe starts from. Value is android.window.BackEvent#EDGE_LEFT, android.window.BackEvent#EDGE_RIGHT, or android.window.BackEvent#EDGE_NONE

BackEvent

Added in API level Baklava
BackEvent(
    touchX: Float, 
    touchY: Float, 
    progress: Float, 
    swipeEdge: Int, 
    frameTimeMillis: Long)

Creates a new BackEvent instance.

Parameters
touchX Float: Absolute X location of the touch point of this event.
touchY Float: Absolute Y location of the touch point of this event.
progress Float: Value between 0 and 1 on how far along the back gesture is.
swipeEdge Int: Indicates which edge the swipe starts from. Value is android.window.BackEvent#EDGE_LEFT, android.window.BackEvent#EDGE_RIGHT, or android.window.BackEvent#EDGE_NONE
frameTimeMillis Long: frame time of the back event.

Public methods

equals

Added in API level 34
fun equals(other: Any?): Boolean
Parameters
obj the reference object with which to compare.
Return
Boolean true if this object is the same as the obj argument; false otherwise.

getFrameTimeMillis

Added in API level Baklava
fun getFrameTimeMillis(): Long

Returns the frameTime of the BackEvent in milliseconds. Useful for calculating velocity.

getProgress

Added in API level 34
fun getProgress(): Float

Returns a value between 0 and 1 on how far along the back gesture is. This value is driven by the horizontal location of the touch point, and should be used as the fraction to seek the predictive back animation with. Specifically,

  1. The progress is 0 when the touch is at the starting edge of the screen (left or right), and animation should seek to its start state.
  2. The progress is approximately 1 when the touch is at the opposite side of the screen, and animation should seek to its end state. Exact end value may vary depending on screen size.
  • After the gesture finishes in cancel state, this method keeps getting invoked until the progress value animates back to 0. In-between locations are linearly interpolated based on horizontal distance from the starting edge and smooth clamped to 1 when the distance exceeds a system-wide threshold.

    • Return
    Float Value is between 0 and 1 inclusive

    getSwipeEdge

    Added in API level 34
    fun getSwipeEdge(): Int

    Returns the screen edge that the swipe starts from.

    Return
    Int Value is android.window.BackEvent#EDGE_LEFT, android.window.BackEvent#EDGE_RIGHT, or android.window.BackEvent#EDGE_NONE

    getTouchX

    Added in API level 34
    fun getTouchX(): Float

    Returns the absolute X location of the touch point, or NaN if the event is from a button press.

    getTouchY

    Added in API level 34
    fun getTouchY(): Float

    Returns the absolute Y location of the touch point, or NaN if the event is from a button press.

    toString

    Added in API level 34
    fun toString(): String
    Return
    String a string representation of the object.