Implement back button in toolbar

[degrigorash]

I'm implementing a toolbar in the overlay view by custom layout with buttons. How can I get the main content to dismiss it like real back button in toolbar?

[frapeti]

ImageViewer imageViewer = new ImageViewer.Builder(MapsActivity.this, images).setStartPosition(0)
                        .hideStatusBar(false)
                        .allowZooming(true)
                        .setBackgroundColorRes(R.color.black)
                        .allowSwipeToDismiss(true)
                        .setOverlayView(overlayView)
                        .show();

overlayView.findViewById(R.id.back_arrow)
        .setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        imageViewer.onDismiss();
                    }
});