Arraylist in a Fragment Activity

Question

I'm trying to have a FragmentActivity where User's input in an Editext can store in an array then will show to Listview but after entering a value and click the button, the application stopped.

I'm having this kind of output in my logcat

02-16 21:53:05.950    1315-1315/com.tipmanila.cite.traventurev2 E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.tipmanila.cite.traventurev2, PID: 1315
    java.lang.NullPointerException
            at com.tipmanila.cite.traventurev2.NotesFragment$1.onClick(NotesFragment.java:53)
            at android.view.View.performClick(View.java:4442)
            at android.view.View$PerformClick.run(View.java:18473)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5105)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
            at dalvik.system.NativeStart.main(Native Method)

My FragmentActivity look like this

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.notes_fragment, container, false);

    txt = (EditText) v.findViewById(R.id.txtInput);
    show = (ListView) v.findViewById(R.id.listView);
    save = (Button) v.findViewById(R.id.btnSave);
    save.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String getInput = txt.getText().toString();

            if (addArray.contains(getInput)) {
                Toast.makeText(getActivity(), "Note already added", Toast.LENGTH_LONG).show();

            } else if (getInput == null || getInput.trim().equals("")){
                Toast.makeText(getActivity(), "Input field is null", Toast.LENGTH_LONG).show();

            } else {
                addArray.add(getInput);
                ArrayAdapter<String> adapter =  new ArrayAdapter<String>(getActivity().getApplicationContext(), android.R.layout.simple_list_item_1, addArray);
                show.setAdapter(adapter);
                ((EditText) v.findViewById(R.id.txtInput)).setText("");

            }


        }
    });


    return v;