The CoordinatorLayout is a super-powered FrameLayout and goal of this ViewGroup is to coordinate the views that are inside it.
The main appeal of the CoordinatorLayout is its ability to coordinate the animations and transitions of the views within the XML file itself.
CoordinatorLayout is intended for two primary use cases:
:As a top-level application decor or chrome layout
:As a container for a specific interaction with one or more child views
The CoordinatorLayout
is a container that extends the FrameLayout
.
By attaching a CoordinatorLayout.Behavior
to a direct child of CoordinatorLayout
, you’ll be able to intercept touch events, window insets, measurement, layout, and nested scrolling.
By specifying Behaviors
for child views of a CoordinatorLayout
you can provide many different interactions within a single parent and those views can also interact with one another. View classes can specify a default behavior when used as a child of a CoordinatorLayout
using the DefaultBehavior
annotation.
To create a Behavior
just extend the CoordinatorLayout.Behavior
class.
Example:
public class MyBehavior<V extends View> extends CoordinatorLayout.Behavior<V> {
/**
* Default constructor.
*/
public MyBehavior() {
}
/**
* Default constructor for inflating a MyBehavior from layout.
*
* @param context The {@link Context}.
* @param attrs The {@link AttributeSet}.
*/
public MyBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
}
This behavior need to be attached to a child View of a CoordinatorLayout
to be called.
MyBehavior myBehavior = new MyBehavior();
CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) view.getLayoutParams();
params.setBehavior(myBehavior);
You can use the layout_behavior
attribute to attach the behavior in XML:
<View
android:layout_height="...."
android:layout_width="...."
app:layout_behavior=".MyBehavior" />
If you are working with a custom view you can attach the behavior using the @CoordinatorLayout.DefaultBehavior
annotation:
@CoordinatorLayout.DefaultBehavior(MyBehavior.class)
public class MyView extends ..... {
}
The SwipeDismissBehavior
works on any View and implements the functionality of swipe to dismiss in our layouts with a CoordinatorLayout
.
Just use:
final SwipeDismissBehavior<MyView> swipe = new SwipeDismissBehavior();
//Sets the swipe direction for this behavior.
swipe.setSwipeDirection(
SwipeDismissBehavior.SWIPE_DIRECTION_ANY);
//Set the listener to be used when a dismiss event occurs
swipe.setListener(
new SwipeDismissBehavior.OnDismissListener() {
@Override public void onDismiss(View view) {
//......
}
@Override
public void onDragStateChanged(int state) {
//......
}
});
//Attach the SwipeDismissBehavior to a view
LayoutParams coordinatorParams =
(LayoutParams) mView.getLayoutParams();
coordinatorParams.setBehavior(swipe);
You can use the CoordinatorLayout.Behavior
to create dependencies between views. You can anchor a View
to another View
by:
layout_anchor
attribute.Behavior
and implementing the layoutDependsOn
method returning true
.For example, in order to create a Behavior
for moving an ImageView
when another one is moved (example Toolbar), perform the following steps:
public class MyBehavior extends CoordinatorLayout.Behavior<ImageView> {...}
Override the layoutDependsOn
method returning true
. This method is called every time a change occurs to the layout:
@Override
public boolean layoutDependsOn(CoordinatorLayout parent,
ImageView child, View dependency) {
// Returns true to add a dependency.
return dependency instanceof Toolbar;
}
Whenever the method layoutDependsOn
returns true
the method onDependentViewChanged
is called:
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, ImageView child, View dependency) {
// Implement here animations, translations, or movements; always related to the provided dependency.
float translationY = Math.min(0, dependency.getTranslationY() - dependency.getHeight());
child.setTranslationY(translationY);
}