CoordinatorLayout.Behavior

public Behavior()

Default constructor for instantiating Behaviors.

public Behavior(@NonNull Context context, @Nullable AttributeSet attrs)

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.

public boolean blocksInteractionBelow(@NonNull CoordinatorLayout parent, @NonNull V child)

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

The default implementation returns true if getScrimOpacity would return >0.0f.

public boolean getInsetDodgeRect(
    @NonNull CoordinatorLayout parent,
    @NonNull V child,
    @NonNull Rect rect
)

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 IllegalArgumentException is thrown.

public @ColorInt int getScrimColor(@NonNull CoordinatorLayout parent, @NonNull V child)

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 BLACK.

public @FloatRange(from = 0, to = 1) float getScrimOpacity(@NonNull CoordinatorLayout parent, @NonNull V child)

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.

public static @Nullable Object getTag(@NonNull View child)

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

public boolean layoutDependsOn(
    @NonNull CoordinatorLayout parent,
    @NonNull V child,
    @NonNull View dependency
)

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 onDependentViewChanged when the dependency view's layout or position changes.

public @NonNull WindowInsetsCompat onApplyWindowInsets(
    @NonNull CoordinatorLayout coordinatorLayout,
    @NonNull V child,
    @NonNull WindowInsetsCompat insets
)

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.

public void onAttachedToLayoutParams(@NonNull CoordinatorLayout.LayoutParams params)

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.

public boolean onDependentViewChanged(
    @NonNull CoordinatorLayout parent,
    @NonNull V child,
    @NonNull View dependency
)

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 layoutDependsOn 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.

public void onDependentViewRemoved(
    @NonNull CoordinatorLayout parent,
    @NonNull V child,
    @NonNull View dependency
)

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 layoutDependsOn or if child has set another view as it's anchor.

public void onDetachedFromLayoutParams()

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 setBehavior. It will not be called if the associated view is removed from the CoordinatorLayout or similar.

public boolean onInterceptTouchEvent(
    @NonNull CoordinatorLayout parent,
    @NonNull V child,
    @NonNull MotionEvent ev
)

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 onTouchEvent 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 isShown on the given child.

The default implementation of this method always returns false.

public boolean onLayoutChild(
    @NonNull CoordinatorLayout parent,
    @NonNull V child,
    int layoutDirection
)

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 onDependentViewChanged 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.

public boolean onMeasureChild(
    @NonNull CoordinatorLayout parent,
    @NonNull V child,
    int parentWidthMeasureSpec,
    int widthUsed,
    int parentHeightMeasureSpec,
    int heightUsed
)

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.