Fragment Implementation

I have an Issue, I cant use this on a fragment, I really like how it looks on a regular activity but also would like to implement it on my fragments. This is what I get.

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.daimajia.slider.library.SliderLayout.addSlider(com.daimajia.slider.library.SliderTypes.BaseSliderView)' on a null object reference

public void startSlider(){
Context contextSl = getActivity().getApplicationContext();
//Set the slider for header images----------------------------------------------------------------------------------Abe Cruz
url_maps = new HashMap();
url_maps.put("Hannibal", "http://static2.hypable.com/wp-content/uploads/2013/12/hannibal-season-2-release-date.jpg");
url_maps.put("Big Bang Theory", "http://tvfiles.alphacoders.com/100/hdclearart-10.png");
url_maps.put("House of Cards", "http://cdn3.nflximg.net/images/3093/2043093.jpg");
url_maps.put("Game of Thrones", "http://images.boomsbeat.com/data/images/full/19640/game-of-thrones-season-4-jpg.jpg");

for(String name : url_maps.keySet()){
TextSliderView textSliderView = new TextSliderView(contextSl);
// initialize a SliderLayout
textSliderView
.description(name)
.image(url_maps.get(name))
.setScaleType(BaseSliderView.ScaleType.Fit)
.setOnSliderClickListener((BaseSliderView.OnSliderClickListener) contextSl);

//add extra information
textSliderView.bundle(new Bundle());
textSliderView.getBundle().putString("extra",name);
mSlider.addSlider(textSliderView);
}
mSlider.setPresetTransformer(SliderLayout.Transformer.FlipPage);
mSlider.setPresetIndicator(SliderLayout.PresetIndicators.Center_Bottom);
mSlider.setCustomAnimation(new DescriptionAnimation());
mSlider.setDuration(4000);
mSlider.addOnPageChangeListener((ViewPagerEx.OnPageChangeListener) contextSl);
//Set the slider for header images----------------------------------------------------------------------------------Abe Cruz
}