null pointer exception in slider menu

Question

public class Search_HotelActivity extends Activity implements OnClickListener {
    Button btnClick;
    Button btnSelect;
    Button btnCancel;
    Button btn_Filter;
    DatePicker dp1;
    int Year, Month, Day;
    TextView tvDate;
    Dialog d;

private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
// nav drawer title
    private CharSequence mDrawerTitle;

    // used to store app title
    private CharSequence mTitle;

    // slide menu items
    private String[] navMenuTitles;
    private TypedArray navMenuIcons;

    private ArrayList<NavDrawerItem> navDrawerItems;
    private NavDrawerListAdapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_search__hotel);

    btnClick = (Button) findViewById(R.id.btnClick);
    btn_Filter=(Button) findViewById(R.id.btn_Filter);
    btnClick.setOnClickListener(this);
    btn_Filter.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            Intent i=new Intent(Search_HotelActivity.this,Filter_Activity.class);
            startActivity(i);

        }});
}

public void onClick(View arg0) {
    // TODO Auto-generated method stub
    switch (arg0.getId()) {
    case R.id.btnClick:
        d = new Dialog(Search_HotelActivity.this);
        d.setContentView(R.layout.dp_dialog);
        d.setTitle("Select Date:");
        dp1 = (DatePicker) d.findViewById(R.id.dp1);
        btnSelect = (Button) d.findViewById(R.id.btnSelect);
        btnCancel = (Button) d.findViewById(R.id.btnCancel);
        btnSelect.setOnClickListener(this);
        btnCancel.setOnClickListener(this);
        final Calendar cal = Calendar.getInstance();
        int year = cal.get(Calendar.YEAR);
        final int monthOfYear = cal.get(Calendar.MONTH);
        int dayOfMonth = cal.get(Calendar.DAY_OF_MONTH);

        dp1.init(year, monthOfYear, dayOfMonth,
                new OnDateChangedListener() {

                    @Override
                    public void onDateChanged(DatePicker arg0, int year,
                            int monthOfyear, int dayOfMonth) {
                        //TODO Auto-generated method stub
                        Year = year;
                        Month = monthOfYear;
                        Day = dayOfMonth;

                    }
                });
        d.show();

        break;
    case R.id.btnSelect:
        tvDate = (TextView) findViewById(R.id.tvDate);
        tvDate.setText(Day + " / " + (Month + 1) + "/" + Year);
        //Toast.makeText(MainActivity.this, "Hours" + tp.getCurrentHour(),
            //  3000).show();
        d.dismiss();
        break;
    case R.id.btnCancel:
        d.dismiss();
        break;
    }
    mTitle = mDrawerTitle = getTitle();

    // load slide menu items
    navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);

    // nav drawer icons from resources
    navMenuIcons = getResources()
            .obtainTypedArray(R.array.nav_drawer_icons);

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawerList = (ListView) findViewById(R.id.list_slidermenu);

    navDrawerItems = new ArrayList<NavDrawerItem>();

    // adding nav drawer items to array
    // Home
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
    // Find People
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
    // Photos
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
    // Communities, Will add a counter here
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "22"));
    // Pages
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
    // What's hot, We  will add a counter here
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "50+"));


    // Recycle the typed array
    navMenuIcons.recycle();

    mDrawerList.setOnItemClickListener(new SlideMenuClickListener());

    // setting the nav drawer list adapter
    adapter = new NavDrawerListAdapter(getApplicationContext(),
            navDrawerItems);
    mDrawerList.setAdapter(adapter);

    // enabling action bar app icon and behaving it as toggle button
    getActionBar().setDisplayHomeAsUpEnabled(true);
    getActionBar().setHomeButtonEnabled(true);

    mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
            R.drawable.ic_drawer, //nav menu toggle icon
            R.string.app_name, // nav drawer open - description for accessibility
            R.string.app_name // nav drawer close - description for accessibility
    ) {
        public void onDrawerClosed(View view) {
            getActionBar().setTitle(mTitle);
            // calling onPrepareOptionsMenu() to show action bar icons
            invalidateOptionsMenu();
        }

        public void onDrawerOpened(View drawerView) {
            getActionBar().setTitle(mDrawerTitle);
            // calling onPrepareOptionsMenu() to hide action bar icons
            invalidateOptionsMenu();
        }
    };
    mDrawerLayout.setDrawerListener(mDrawerToggle);

    Object savedInstanceState = null;
    if (savedInstanceState == null) {
        // on first time display view for first nav item
        displayView(0);
    }

}
/**
 * Slide menu item click listener
 * */
private class SlideMenuClickListener implements
        ListView.OnItemClickListener {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position,
            long id) {
        // display view for selected nav drawer item
        displayView(position);
    }
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.search__hotel, menu);
    return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // toggle nav drawer on selecting action bar app icon/title
    if (mDrawerToggle.onOptionsItemSelected(item)) {
        return true;
    }
    // Handle action bar actions click
    switch (item.getItemId()) {
    case R.id.action_settings:
        return true;
    default:
        return super.onOptionsItemSelected(item);
    }
}

/* *
 * Called when invalidateOptionsMenu() is triggered
 */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
    // if nav drawer is opened, hide the action items
    boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
    menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
    return super.onPrepareOptionsMenu(menu);
}

/**
 * Diplaying fragment view for selected nav drawer list item
 * */
private void displayView(int position) {
    // update the main content by replacing fragments
    Fragment fragment = null;
    switch (position) {
    case 0:
        fragment = new HomeFragment();
        break;
    case 1:
        fragment = new FindPeopleFragment();
        break;
    case 2:
        fragment = new PhotosFragment();
        break;
    case 3:
        fragment = new CommunityFragment();
        break;
    case 4:
        fragment = new PagesFragment();
        break;
    case 5:
        fragment = new WhatsHotFragment();
        break;

    default:
        break;
    }

    if (fragment != null) {
        FragmentManager fragmentManager = getFragmentManager();
        fragmentManager.beginTransaction()
                .replace(R.id.frame_container, fragment).commit();

        // update selected item and title, then close the drawer
        mDrawerList.setItemChecked(position, true);
        mDrawerList.setSelection(position);
        setTitle(navMenuTitles[position]);
        mDrawerLayout.closeDrawer(mDrawerList);
    } else {
        // error in creating fragment
        Log.e("MainActivity", "Error in creating fragment");
    }
}

@Override
public void setTitle(CharSequence title) {
    mTitle = title;
    getActionBar().setTitle(mTitle);
}

/**
 * When using the ActionBarDrawerToggle, you must call it during
 * onPostCreate() and onConfigurationChanged()...
 */

@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    // Sync the toggle state after onRestoreInstanceState has occurred.
    mDrawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    // Pass any configuration change to the drawer toggls
    mDrawerToggle.onConfigurationChanged(newConfig);
}

}