MovableFloatingActionButton.java

import android.content.Context;
import android.support.design.widget.CoordinatorLayout;
import android.support.design.widget.FloatingActionButton;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;


/**
 * Created by matteo on 25/01/2018.
 */

public class MovableFloatingActionButton extends FloatingActionButton implements View.OnTouchListener {

    private final static float CLICK_DRAG_TOLERANCE = 10; // Often, there will be a slight, unintentional, drag when the user taps the FAB, so we need to account for this.

    private float downRawX, downRawY;
    private float dX, dY;

    private CoordinatorLayout.LayoutParams coordinatorLayout;

    public MovableFloatingActionButton(Context context) {
        super(context);
        init();
    }

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

    public MovableFloatingActionButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }


    private void init() {
        setOnTouchListener(this);
    }

    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {
        View viewParent;
        switch (motionEvent.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                Log.d("MovableFAB", "ACTION_DOWN");
                downRawX = motionEvent.getRawX();
                downRawY = motionEvent.getRawY();
                dX = view.getX() - downRawX;
                dY = view.getY() - downRawY;

                return true; // Consumed

            case MotionEvent.ACTION_MOVE:
                int viewWidth = view.getWidth();
                int viewHeight = view.getHeight();

                viewParent = (View) view.getParent();
                int parentWidth = viewParent.getWidth();
                int parentHeight = viewParent.getHeight();

                float newX = motionEvent.getRawX() + dX;
                newX = Math.max(0, newX); // Don't allow the FAB past the left hand side of the parent
                newX = Math.min(parentWidth - viewWidth, newX); // Don't allow the FAB past the right hand side of the parent

                float newY = motionEvent.getRawY() + dY;
                newY = Math.max(0, newY); // Don't allow the FAB past the top of the parent
                newY = Math.min(parentHeight - viewHeight, newY); // Don't allow the FAB past the bottom of the parent

                view.animate()
                        .x(newX)
                        .y(newY)
                        .setDuration(0)
                        .start();
                return true; // Consumed

            case MotionEvent.ACTION_UP:


                float upRawX = motionEvent.getRawX();
                float upRawY = motionEvent.getRawY();

                float upDX = upRawX - downRawX;
                float upDY = upRawY - downRawY;

                if((Math.abs(upDX) < CLICK_DRAG_TOLERANCE && Math.abs(upDY) < CLICK_DRAG_TOLERANCE) && performClick())
                    return true;

                View viewParent2 = (View) view.getParent();
                float borderY,borderX;
                float oldX=view.getX(), oldY=view.getY();
                float finalX,finalY;

                borderY = Math.min(view.getY()-viewParent2.getTop(),viewParent2.getBottom()-view.getY());
                borderX = Math.min(view.getX()-viewParent2.getLeft(),viewParent2.getRight()-view.getX());
                
		//You can set your dp margin from dimension resources (Suggested)
		//float fab_margin= getResources().getDimension(R.dimen.fab_margin);
		float fab_margin=15;

                //check if is nearest Y o X
                if(borderX>borderY) {
                    if(view.getY()>viewParent2.getHeight()/2) { //view near Bottom
                        finalY = viewParent2.getBottom() - view.getHeight();
                        finalY = Math.min(viewParent2.getHeight() - view.getHeight(), finalY) - fab_margin; // Don't allow the FAB past the bottom of the parent
                    }
                    else {  //view vicina a Top
                        finalY = viewParent2.getTop();
                        finalY = Math.max(0, finalY) + fab_margin; // Don't allow the FAB past the top of the parent
                    }
                    //check if X it's over fab_margin
                    finalX=oldX;
                    if(view.getX()+viewParent2.getLeft()<fab_margin)
                        finalX=viewParent2.getLeft()+fab_margin;
                    if(viewParent2.getRight()-view.getX()-view.getWidth()<fab_margin)
                        finalX=viewParent2.getRight()- view.getWidth()-fab_margin;
                }
                else {  //view near Right
                    if(view.getX()>viewParent2.getWidth()/2) {
                        finalX = viewParent2.getRight() - view.getWidth();
                        finalX = Math.max(0, finalX) - fab_margin; // Don't allow the FAB past the left hand side of the parent
                    }
                    else {  //view near Left
                        finalX = viewParent2.getLeft();
                        finalX = Math.min(viewParent2.getWidth() - view.getWidth(), finalX) + fab_margin; // Don't allow the FAB past the right hand side of the parent
                    }
                    //check if Y it's over fab_margin
                    finalY=oldY;
                    if(view.getY()+viewParent2.getTop()<fab_margin)
                        finalY=viewParent2.getTop()+fab_margin;
                    if(viewParent2.getBottom()-view.getY()-view.getHeight()<fab_margin)
                        finalY=viewParent2.getBottom()-view.getHeight()-fab_margin;
                }

                view.animate()
                        .x(finalX)
                        .y(finalY)
                        .setDuration(400)
                        .start();

                Log.d("MovableFAB", "ACTION_UP");
                return false;

                // A drag consumed
            default:
                return super.onTouchEvent(motionEvent);
            }

        }

    public CoordinatorLayout.LayoutParams getCoordinatorLayout() {
        return coordinatorLayout;
    }

    public void setCoordinatorLayout(CoordinatorLayout.LayoutParams coordinatorLayout) {
        this.coordinatorLayout = coordinatorLayout;
    }
}