Activity is starting slowly

Question

There are several buttons in my app. New activity starts quickly whenever i press any button except for one. It lags to open a new activity.Why it is lagging ? Here is the code snipet :

        Intent intent = new Intent(this, ChooseActivity.class);
        startActivityForResult(intent, Constant.MP_REQUEST);

ChooseActivity.class:

    ChooseActivityHelper mActivityHelper;

    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity);
    mActivityHelper = new ChooseActivityHelper(this);

    mActivityHelper.inflateView();
}

ChooseActivityHelper:

public ChooseActivityHelper(Context ctx) {
    mCurrentTabIndex = 1;
    mContext = ctx;
}

// inflate data to view
    @SuppressLint("UseSparseArrays")
    public void inflateView() {
        ChooseActivity act = (ChooseActivity) mContext;
        try {
            assMngr = act.getAssets();
            String[] folders = assMngr.list(Constant._FOLDER);
            for (String f : folders) {
                inflateTabView(f);
                stampFolderList.add(f);
            }

        } catch (IOException e) {

            e.printStackTrace();
        }

    }