BottomSheetBehavior with support for multiple callbacks

ProxyBottomSheetBehavior.java

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomSheetBehavior;
import android.util.AttributeSet;
import android.view.View;

import java.util.ArrayList;

/**
 * Wrapper around {@link BottomSheetBehavior} with support for multiple callbacks.
 */
public class ProxyBottomSheetBehavior<V extends View> extends BottomSheetBehavior<V> {

    private final BottomSheetCallback proxyCallback = new BottomSheetCallback() {
        @Override
        public void onSlide(@NonNull View bottomSheet, float slideOffset) {
            for (int i = 0; i < callbacks.size(); ++i) {
                callbacks.get(i).onSlide(bottomSheet, slideOffset);
            }
        }

        @Override
        public void onStateChanged(@NonNull View bottomSheet, int newState) {
            for (int i = 0; i < callbacks.size(); ++i) {
                callbacks.get(i).onStateChanged(bottomSheet, newState);
            }
        }
    };
    private final ArrayList<BottomSheetCallback> callbacks = new ArrayList<>();

    public ProxyBottomSheetBehavior() {
    }

    public ProxyBottomSheetBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public void addBottomSheetCallback(BottomSheetCallback callback) {
        if (!callbacks.contains(callback)) {
            callbacks.add(callback);
        }
        setBottomSheetCallback(proxyCallback);
    }

    public void removeBottomSheetCallback(BottomSheetCallback callback) {
        callbacks.remove(callback);
    }

    public static <V extends View> ProxyBottomSheetBehavior<V> from(V view) {
        return (ProxyBottomSheetBehavior<V>) BottomSheetBehavior.from(view);
    }

}