FabLayout with center ,left or right position

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    
    <declare-styleable name="FABCenterLayout">
        <attr name="top_id" format="reference"/>
        <attr name="location" format="enum">
            <enum name="left" value="0" />
            <enum name="right" value="1" />
            <enum name="center" value="2" />
        </attr>
    </declare-styleable>

</resources>

FABCenterLayout.java

package com.worldline.evasdk.view.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;
import android.widget.Toast;

import com.getbase.floatingactionbutton.AddFloatingActionButton;
import com.nineoldandroids.view.ViewHelper;
import com.worldline.evasdk.R;


/**
 * Created by Bernat on 26/08/2014.
 */
public class FABCenterLayout extends RelativeLayout {

    private static final int LOCATION_LEFT = 0;
    private static final int LOCATION_RIGHT = 1;
    private static final int LOCATION_CENTER = 2;

    private int topId;

    private OnClickListener fabClickListener;

    private boolean fabVisible;
    private int fabLocation;
    private String fabTag;
    private AddFloatingActionButton fabView;

    private View topView;
    private View[] translatableViews;

    public FABCenterLayout(Context context) {
        super(context);
        init(null, 0);
    }


    public FABCenterLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(attrs, 0);
    }


    public FABCenterLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(attrs, defStyle);
    }


    private void init(AttributeSet attrs, int defStyle) {
        isInEditMode();

        if (attrs != null) {
            TypedArray attr = getContext().obtainStyledAttributes(attrs, R.styleable.FABCenterLayout, defStyle, 0);

            if (attr.hasValue(R.styleable.FABCenterLayout_top_id)) {
                topId = attr.getResourceId(R.styleable.FABCenterLayout_top_id, 0);
                if (topId != 0) {
                    fabVisible = true;
                    createFabView();
                }

                fabLocation = attr.getInt(R.styleable.FABCenterLayout_location, LOCATION_RIGHT);

                attr.recycle();
            }
        }
    }

    private void createFabView() {
        fabView = (AddFloatingActionButton) LayoutInflater.from(getContext()).inflate(R.layout.fab, this, false);
        ViewCompat.setElevation(fabView, 6f);

        fabView.setOnClickListener(fabClickListener);
        setFabTag();
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);

        if (topView != null && fabVisible && fabView != null) {

            int bottom = topView.getBottom();

            if (bottom > 0) {
                int int8 = getResources().getDimensionPixelOffset(R.dimen.gapMedium);
                if (fabLocation == LOCATION_LEFT) {
                    fabView.layout(l + int8, bottom - fabView.getHeight() / 2, l + int8 + fabView.getWidth(), bottom + fabView.getHeight() / 2);
                } else if (fabLocation == LOCATION_RIGHT) {
                    fabView.layout(r - fabView.getWidth() - int8, bottom - fabView.getHeight() / 2, r - int8, bottom + fabView.getHeight() / 2);
                } else if (fabLocation == LOCATION_CENTER) {
                    int centerX = (topView.getRight() - topView.getLeft()) / 2;
                    fabView.layout(centerX - fabView.getWidth() / 2, bottom - fabView.getHeight() / 2, centerX + fabView.getWidth() / 2, bottom + fabView.getHeight() / 2);
                }
                removeView(fabView);
                addView(fabView);

            }
        }
    }

    public void setFabIcon(Drawable drawable) {
        if (fabView != null) {
            fabView.setImageDrawable(drawable);
        }
    }

    public void setFabClickListener(OnClickListener fabClickListener, final String tag) {
        this.fabClickListener = fabClickListener;
        this.fabTag = tag;
        if (fabView != null) {
            fabView.setOnClickListener(fabClickListener);
            setFabTag();
        }
    }


    private void setFabTag() {
        if (fabView != null && fabTag != null) {
            fabView.setTag(fabTag);
            fabView.setOnLongClickListener(new OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    Toast.makeText(v.getContext(), String.valueOf(v.getTag()), Toast.LENGTH_SHORT).show();
                    return true;
                }
            });
        }
    }

    public void setFabViewVisibility(int visibility) {
        if (fabView != null) {
            fabView.setVisibility(visibility);
        }
    }

    public void translateHeader(float scroll) {

        ViewHelper.setTranslationY(topView, scroll);
        int size = topView.getHeight();
        if (translatableViews != null) {
            for (View translatableView : translatableViews) {
                size -= translatableView.getHeight();
                ViewHelper.setTranslationY(translatableView, scroll);
            }
        }
        size += (fabView.getHeight() / 2);
        if (scroll > -size) {
            ViewHelper.setTranslationY(fabView, scroll);
        } else {
            ViewHelper.setTranslationY(fabView, scroll + (fabView.getHeight() / 2));
        }
    }

    public int getFabId() {
        return fabView != null ? fabView.getId() : 0;
    }

    @Override
    public void addView(View child, int index, ViewGroup.LayoutParams params) {
        super.addView(child, index, params);
        if (child.getId() == topId) {
            topView = child;
        } else {
            View viewTop = child.findViewById(topId);
            if (topView == null && viewTop != null) {
                topView = viewTop;
            }
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        int count = getChildCount();


        int width = getMeasuredWidth();
        int height = 0;
        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            if (child != fabView) {
                height += child.getHeight();
            }
        }

        setMeasuredDimension(width, height);
    }

    public void addTranslatableViews(View... views) {
        translatableViews = views;
    }
}