Overview

Interaction behavior plugin for child views of CoordinatorLayout.

A Behavior implements one or more interactions that a user can take on a child view. These interactions may include drags, swipes, flings, or any other gestures.

Summary

Constructors

Default constructor for instantiating Behaviors.

Default constructor for inflating Behaviors from layout. The Behavior will have the opportunity to parse specially defined layout parameters. These parameters will appear on the child view tag.

Parameters:

context:
attrs:

Methods

Called when the Behavior has been attached to a LayoutParams instance.

This will be called after the LayoutParams has been instantiated and can be modified.

Parameters:

params: the LayoutParams instance that this Behavior has been attached to

Called when the Behavior has been detached from its holding LayoutParams instance.

This will only be called if the Behavior has been explicitly removed from the LayoutParams instance via CoordinatorLayout.LayoutParams. It will not be called if the associated view is removed from the CoordinatorLayout or similar.

Respond to CoordinatorLayout touch events before they are dispatched to child views.

Behaviors can use this to monitor inbound touch events until one decides to intercept the rest of the event stream to take an action on its associated child view. This method will return false until it detects the proper intercept conditions, then return true once those conditions have occurred.

Once a Behavior intercepts touch events, the rest of the event stream will be sent to the CoordinatorLayout.Behavior.onTouchEvent(CoordinatorLayout, V, MotionEvent) method.

This method will be called regardless of the visibility of the associated child of the behavior. If you only wish to handle touch events when the child is visible, you should add a check to View on the given child.

The default implementation of this method always returns false.

Parameters:

parent: the parent view currently receiving this touch event
child: the child view associated with this Behavior
ev: the MotionEvent describing the touch event being processed

Returns:

true if this Behavior would like to intercept and take over the event stream. The default always returns false.

Respond to CoordinatorLayout touch events after this Behavior has started intercepting them.

Behaviors may intercept touch events in order to help the CoordinatorLayout manipulate its child views. For example, a Behavior may allow a user to drag a UI pane open or closed. This method should perform actual mutations of view layout state.

This method will be called regardless of the visibility of the associated child of the behavior. If you only wish to handle touch events when the child is visible, you should add a check to View on the given child.

Parameters:

parent: the parent view currently receiving this touch event
child: the child view associated with this Behavior
ev: the MotionEvent describing the touch event being processed

Returns:

true if this Behavior handled this touch event and would like to continue receiving events in this stream. The default always returns false.

Supply a scrim color that will be painted behind the associated child view.

A scrim may be used to indicate that the other elements beneath it are not currently interactive or actionable, drawing user focus and attention to the views above the scrim.

The default implementation returns .

Parameters:

parent: the parent view of the given child
child: the child view above the scrim

Returns:

the desired scrim color in 0xAARRGGBB format. The default return value is .

See also: CoordinatorLayout.Behavior.getScrimOpacity(CoordinatorLayout, V)

Determine the current opacity of the scrim behind a given child view

A scrim may be used to indicate that the other elements beneath it are not currently interactive or actionable, drawing user focus and attention to the views above the scrim.

The default implementation returns 0.0f.

Parameters:

parent: the parent view of the given child
child: the child view above the scrim

Returns:

the desired scrim opacity from 0.0f to 1.0f. The default return value is 0.0f.

Determine whether interaction with views behind the given child in the child order should be blocked.

The default implementation returns true if CoordinatorLayout.Behavior.getScrimOpacity(CoordinatorLayout, V) would return > 0.0f.

Parameters:

parent: the parent view of the given child
child: the child view to test

Returns:

true if CoordinatorLayout.Behavior.getScrimOpacity(CoordinatorLayout, V) would return > 0.0f.

Determine whether the supplied child view has another specific sibling view as a layout dependency.

This method will be called at least once in response to a layout request. If it returns true for a given child and dependency view pair, the parent CoordinatorLayout will:

1. Always lay out this child after the dependent child is laid out, regardless of child order.
2. Call CoordinatorLayout.Behavior.onDependentViewChanged(CoordinatorLayout, V, View) when the dependency view's layout or position changes.

Parameters:

parent: the parent view of the given child
child: the child view to test
dependency: the proposed dependency of child

Returns:

true if child's layout depends on the proposed dependency's layout, false otherwise

See also: CoordinatorLayout.Behavior.onDependentViewChanged(CoordinatorLayout, V, View)

Respond to a change in a child's dependent view

This method is called whenever a dependent view changes in size or position outside of the standard layout flow. A Behavior may use this method to appropriately update the child view in response.

A view's dependency is determined by CoordinatorLayout.Behavior.layoutDependsOn(CoordinatorLayout, V, View) or if child has set another view as it's anchor.

Note that if a Behavior changes the layout of a child via this method, it should also be able to reconstruct the correct position in onLayoutChild. onDependentViewChanged will not be called during normal layout since the layout of each child view will always happen in dependency order.

If the Behavior changes the child view's size or position, it should return true. The default implementation returns false.

Parameters:

parent: the parent view of the given child
child: the child view to manipulate
dependency: the dependent view that changed

Returns:

true if the Behavior changed the child view's size or position, false otherwise

Respond to a child's dependent view being removed.

This method is called after a dependent view has been removed from the parent. A Behavior may use this method to appropriately update the child view in response.

A view's dependency is determined by CoordinatorLayout.Behavior.layoutDependsOn(CoordinatorLayout, V, View) or if child has set another view as it's anchor.

Parameters:

parent: the parent view of the given child
child: the child view to manipulate
dependency: the dependent view that has been removed

Called when the parent CoordinatorLayout is about to measure the given child view.

This method can be used to perform custom or modified measurement of a child view in place of the default child measurement behavior. The Behavior's implementation can delegate to the standard CoordinatorLayout measurement behavior by calling parent.onMeasureChild.

Parameters:

parent: the parent CoordinatorLayout
child: the child to measure
parentWidthMeasureSpec: the width requirements for this view
widthUsed: extra space that has been used up by the parent horizontally (possibly by other children of the parent)
parentHeightMeasureSpec: the height requirements for this view
heightUsed: extra space that has been used up by the parent vertically (possibly by other children of the parent)

Returns:

true if the Behavior measured the child view, false if the CoordinatorLayout should perform its default measurement

Called when the parent CoordinatorLayout is about the lay out the given child view.

This method can be used to perform custom or modified layout of a child view in place of the default child layout behavior. The Behavior's implementation can delegate to the standard CoordinatorLayout measurement behavior by calling parent.onLayoutChild.

If a Behavior implements CoordinatorLayout.Behavior.onDependentViewChanged(CoordinatorLayout, V, View) to change the position of a view in response to a dependent view changing, it should also implement onLayoutChild in such a way that respects those dependent views. onLayoutChild will always be called for a dependent view after its dependency has been laid out.

Parameters:

parent: the parent CoordinatorLayout
child: child view to lay out
layoutDirection: the resolved layout direction for the CoordinatorLayout, such as ViewCompat.LAYOUT_DIRECTION_LTR or ViewCompat.LAYOUT_DIRECTION_RTL.

Returns:

true if the Behavior performed layout of the child view, false to request default layout behavior

Associate a Behavior-specific tag object with the given child view. This object will be stored with the child view's LayoutParams.

Parameters:

child: child view to set tag with
tag: tag object to set

Get the behavior-specific tag object with the given child view. This object is stored with the child view's LayoutParams.

Parameters:

child: child view to get tag with

Returns:

the previously stored tag object

Deprecated: You should now override CoordinatorLayout.Behavior.onStartNestedScroll(CoordinatorLayout, V, View, View, int, int). This method will still continue to be called if the type is ViewCompat.TYPE_TOUCH.

Called when a descendant of the CoordinatorLayout attempts to initiate a nested scroll.

Any Behavior associated with any direct child of the CoordinatorLayout may respond to this event and return true to indicate that the CoordinatorLayout should act as a nested scrolling parent for this scroll. Only Behaviors that return true from this method will receive subsequent nested scroll events.

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
directTargetChild: the child view of the CoordinatorLayout that either is or contains the target of the nested scroll operation
target: the descendant view of the CoordinatorLayout initiating the nested scroll
axes: the axes that this nested scroll applies to. See ViewCompat.SCROLL_AXIS_HORIZONTAL, ViewCompat.SCROLL_AXIS_VERTICAL
type: the type of input which cause this scroll event

Returns:

true if the Behavior wishes to accept this nested scroll

See also: NestedScrollingParent2.onStartNestedScroll(View, View, int, int)

Deprecated: You should now override CoordinatorLayout.Behavior.onNestedScrollAccepted(CoordinatorLayout, V, View, View, int, int). This method will still continue to be called if the type is ViewCompat.TYPE_TOUCH.

Called when a nested scroll has been accepted by the CoordinatorLayout.

Any Behavior associated with any direct child of the CoordinatorLayout may elect to accept the nested scroll as part of CoordinatorLayout.Behavior.onStartNestedScroll(CoordinatorLayout, V, View, View, int). Each Behavior that returned true will receive subsequent nested scroll events for that nested scroll.

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
directTargetChild: the child view of the CoordinatorLayout that either is or contains the target of the nested scroll operation
target: the descendant view of the CoordinatorLayout initiating the nested scroll
axes: the axes that this nested scroll applies to. See ViewCompat.SCROLL_AXIS_HORIZONTAL, ViewCompat.SCROLL_AXIS_VERTICAL
type: the type of input which cause this scroll event

See also: NestedScrollingParent2.onNestedScrollAccepted(View, View, int, int)

Deprecated: You should now override CoordinatorLayout.Behavior.onStopNestedScroll(CoordinatorLayout, V, View, int). This method will still continue to be called if the type is ViewCompat.TYPE_TOUCH.

Called when a nested scroll has ended.

Any Behavior associated with any direct child of the CoordinatorLayout may elect to accept the nested scroll as part of CoordinatorLayout.Behavior.onStartNestedScroll(CoordinatorLayout, V, View, View, int). Each Behavior that returned true will receive subsequent nested scroll events for that nested scroll.

onStopNestedScroll marks the end of a single nested scroll event sequence. This is a good place to clean up any state related to the nested scroll.

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
target: the descendant view of the CoordinatorLayout that initiated the nested scroll
type: the type of input which cause this scroll event

See also: NestedScrollingParent2.onStopNestedScroll(View, int)

Deprecated: You should now override CoordinatorLayout.Behavior.onNestedScroll(CoordinatorLayout, V, View, int, int, int, int, int, int[]). This method will still continue to be called if neither CoordinatorLayout.Behavior.onNestedScroll(CoordinatorLayout, V, View, int, int, int, int, int, int[]) nor CoordinatorLayout.onNestedScroll(View, int, int, int, int, int) are overridden and the type is ViewCompat.TYPE_TOUCH.

Deprecated: You should now override CoordinatorLayout.Behavior.onNestedScroll(CoordinatorLayout, V, View, int, int, int, int, int, int[]). This method will still continue to be called if CoordinatorLayout.Behavior.onNestedScroll(CoordinatorLayout, V, View, int, int, int, int, int, int[]) is not overridden.

Called when a nested scroll in progress has updated and the target has scrolled or attempted to scroll.

Any Behavior associated with the direct child of the CoordinatorLayout may elect to accept the nested scroll as part of CoordinatorLayout.Behavior.onStartNestedScroll(CoordinatorLayout, V, View, View, int). Each Behavior that returned true will receive subsequent nested scroll events for that nested scroll.

onNestedScroll is called each time the nested scroll is updated by the nested scrolling child, with both consumed and unconsumed components of the scroll supplied in pixels. Each Behavior responding to the nested scroll will receive the same values.

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
target: the descendant view of the CoordinatorLayout performing the nested scroll
dxConsumed: horizontal pixels consumed by the target's own scrolling operation
dyConsumed: vertical pixels consumed by the target's own scrolling operation
dxUnconsumed: horizontal pixels not consumed by the target's own scrolling operation, but requested by the user
dyUnconsumed: vertical pixels not consumed by the target's own scrolling operation, but requested by the user
type: the type of input which cause this scroll event
consumed: output. Upon this method returning, should contain the scroll distances consumed by this Behavior

See also: NestedScrollingParent3.onNestedScroll(View, int, int, int, int, int, int[])

Deprecated: You should now override CoordinatorLayout.Behavior.onNestedPreScroll(CoordinatorLayout, V, View, int, int, int[], int). This method will still continue to be called if the type is ViewCompat.TYPE_TOUCH.

Called when a nested scroll in progress is about to update, before the target has consumed any of the scrolled distance.

Any Behavior associated with the direct child of the CoordinatorLayout may elect to accept the nested scroll as part of CoordinatorLayout.Behavior.onStartNestedScroll(CoordinatorLayout, V, View, View, int). Each Behavior that returned true will receive subsequent nested scroll events for that nested scroll.

onNestedPreScroll is called each time the nested scroll is updated by the nested scrolling child, before the nested scrolling child has consumed the scroll distance itself. Each Behavior responding to the nested scroll will receive the same values. The CoordinatorLayout will report as consumed the maximum number of pixels in either direction that any Behavior responding to the nested scroll reported as consumed.

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
target: the descendant view of the CoordinatorLayout performing the nested scroll
dx: the raw horizontal number of pixels that the user attempted to scroll
dy: the raw vertical number of pixels that the user attempted to scroll
consumed: out parameter. consumed[0] should be set to the distance of dx that was consumed, consumed[1] should be set to the distance of dy that was consumed
type: the type of input which cause this scroll event

See also: NestedScrollingParent2.onNestedPreScroll(View, int, int, int[], int)

Called when a nested scrolling child is starting a fling or an action that would be a fling.

Any Behavior associated with the direct child of the CoordinatorLayout may elect to accept the nested scroll as part of CoordinatorLayout.Behavior.onStartNestedScroll(CoordinatorLayout, V, View, View, int). Each Behavior that returned true will receive subsequent nested scroll events for that nested scroll.

onNestedFling is called when the current nested scrolling child view detects the proper conditions for a fling. It reports if the child itself consumed the fling. If it did not, the child is expected to show some sort of overscroll indication. This method should return true if it consumes the fling, so that a child that did not itself take an action in response can choose not to show an overfling indication.

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
target: the descendant view of the CoordinatorLayout performing the nested scroll
velocityX: horizontal velocity of the attempted fling
velocityY: vertical velocity of the attempted fling
consumed: true if the nested child view consumed the fling

Returns:

true if the Behavior consumed the fling

See also: NestedScrollingParent.onNestedFling(View, float, float, boolean)

Called when a nested scrolling child is about to start a fling.

Any Behavior associated with the direct child of the CoordinatorLayout may elect to accept the nested scroll as part of CoordinatorLayout.Behavior.onStartNestedScroll(CoordinatorLayout, V, View, View, int). Each Behavior that returned true will receive subsequent nested scroll events for that nested scroll.

onNestedPreFling is called when the current nested scrolling child view detects the proper conditions for a fling, but it has not acted on it yet. A Behavior can return true to indicate that it consumed the fling. If at least one Behavior returns true, the fling should not be acted upon by the child.

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
target: the descendant view of the CoordinatorLayout performing the nested scroll
velocityX: horizontal velocity of the attempted fling
velocityY: vertical velocity of the attempted fling

Returns:

true if the Behavior consumed the fling

See also: NestedScrollingParent.onNestedPreFling(View, float, float)

Called when the window insets have changed.

Any Behavior associated with the direct child of the CoordinatorLayout may elect to handle the window inset change on behalf of it's associated view.

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
insets: the new window insets.

Returns:

The insets supplied, minus any insets that were consumed

Called when a child of the view associated with this behavior wants a particular rectangle to be positioned onto the screen.

The contract for this method is the same as .

Parameters:

coordinatorLayout: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
rectangle: The rectangle which the child wishes to be on the screen in the child's coordinates
immediate: true to forbid animated or delayed scrolling, false otherwise

Returns:

true if the Behavior handled the request

See also:

Hook allowing a behavior to re-apply a representation of its internal state that had previously been generated by CoordinatorLayout.Behavior.onSaveInstanceState(CoordinatorLayout, V). This function will never be called with a null state.

Parameters:

parent: the parent CoordinatorLayout
child: child view to restore from
state: The frozen state that had previously been returned by CoordinatorLayout.Behavior.onSaveInstanceState(CoordinatorLayout, V).

See also: CoordinatorLayout.onSaveInstanceState()

Hook allowing a behavior to generate a representation of its internal state that can later be used to create a new instance with that same state. This state should only contain information that is not persistent or can not be reconstructed later.

Behavior state is only saved when both the parent CoordinatorLayout and a view using this behavior have valid IDs set.

Parameters:

parent: the parent CoordinatorLayout
child: child view to restore from

Returns:

Returns a Parcelable object containing the behavior's current dynamic state.

See also: CoordinatorLayout.onRestoreInstanceState(Parcelable), View

Called when a view is set to dodge view insets.

This method allows a behavior to update the rectangle that should be dodged. The rectangle should be in the parent's coordinate system and within the child's bounds. If not, a java.lang.IllegalArgumentException is thrown.

Parameters:

parent: the CoordinatorLayout parent of the view this Behavior is associated with
child: the child view of the CoordinatorLayout this Behavior is associated with
rect: the rect to update with the dodge rectangle

Returns:

true the rect was updated, false if we should use the child's bounds