Create dependencies between Views

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You can use the CoordinatorLayout.Behavior to create dependencies between views. You can anchor a View to another View by:

using the layout_anchor attribute.
creating a custom 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:

Create the custom Behavior:

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);
}

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