the camera button not working

package hemanth.example.com.connect;

import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.ListFragment;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.app.FragmentPagerAdapter;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.TextView;
import android.widget.Toast;

import com.parse.ParseAnalytics;
import com.parse.ParseUser;


public class MainActivity extends ActionBarActivity implements ActionBar.TabListener {

    private Uri mUri;


    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
    may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */
    SectionsPagerAdapter mSectionsPagerAdapter;
    protected DialogInterface.OnClickListener mlisitner= new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            switch (which){

                case 0 :
                    Intent take_photo = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                    mUri = getFileUri(4);
                    if(mUri==null)
                    {

                        Toast.makeText(MainActivity.this,"Check Your SD Card",Toast.LENGTH_LONG).show();
                    }
                    take_photo.putExtra(MediaStore.EXTRA_OUTPUT,mUri);
                    startActivityForResult(take_photo, 0);
                    break;
                case 1:
                    break;
                case 2:
                    break;

            }
        }


        private Uri getFileUri(int mediaType) {

            if(isExternalStorageAvailable()){

                //get the external storage directory

                File mediaStorage = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
                        "Connect");

                // create a sub directory for the app

                if(!mediaStorage.exists()){

                    if(! mediaStorage.mkdirs()){
                        Log.e(MainActivity.class.getSimpleName(),"Failed To create directory");
                        return null;
                    }

                }
                // create file name

                //create file

                File mediaFile;
                Date now = new Date();
                String time = new SimpleDateFormat("yyyyMMdd_HHmmss",Locale.UK).format(now);
                String path = mediaStorage.getPath() + File.separator;
                if(mediaType == 4){
                    mediaFile = new File(path + "IMG_" + time + ".jpg");
                }
                else if(mediaType==5){
                    mediaFile = new File(path + "VID_"+time+".mp4");
                }
                else {

                    return null;
                }

                // return file uri

                return Uri.fromFile(mediaFile);

            }
            else
            {
                return null;
            }
        }
        private boolean isExternalStorageAvailable(){

            String state = Environment.getExternalStorageState();

            if(state.equals(Environment.MEDIA_MOUNTED)){

                return true;

            }
            else{
                return false;
            }
        }
    };

    /**
     * The {@link ViewPager} that will host the section contents.
     */
    ViewPager mViewPager;
    public static final String TAG = MainActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ParseUser currentUser = ParseUser.getCurrentUser();
        if (currentUser == null) {
            navigateToLogin();
        } else {
            Log.i(TAG, currentUser.getUsername());
        }

        // Set up the action bar.
        final ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        // When swiping between different sections, select the corresponding
        // tab. We can also use ActionBar.Tab#select() to do this if we have
        // a reference to the Tab.
        mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                actionBar.setSelectedNavigationItem(position);
            }
        });

        // For each of the sections in the app, add a tab to the action bar.
        for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
            // Create a tab with text corresponding to the page title defined by
            // the adapter. Also specify this Activity object, which implements
            // the TabListener interface, as the callback (listener) for when
            // this tab is selected.
            actionBar.addTab(
                    actionBar.newTab()
                            .setText(mSectionsPagerAdapter.getPageTitle(i))
                            .setTabListener(this));


        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(resultCode == RESULT_OK)
        {
            //IT IS SUCCESSFUL
            //sending broadcast
            Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
            mediaScanIntent.setData(mUri);
            sendBroadcast(mediaScanIntent);
        }
        else if(resultCode==RESULT_CANCELED){
            Toast.makeText(this,"Some error has popped",Toast.LENGTH_LONG).show();
        }
    }

    private void navigateToLogin() {
        Intent intent = new Intent(this, login_activity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(intent);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        switch (id)
        {
            case R.id.action_logout:
                ParseUser.logOut();
                navigateToLogin();
                break;

            case R.id.action_addfriends:

                Intent intent = new Intent(this,EditFriendsActivity.class);
                startActivity(intent);
                break;

            case R.array.camera_choices:

                AlertDialog.Builder builder = new AlertDialog.Builder(this);
                builder.setItems(R.array.camera_choices,mlisitner);
                AlertDialog dialog = builder.create();
                dialog.show();
                break;

        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
        // When the given tab is selected, switch to the corresponding page in
        // the ViewPager.
        mViewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a PlaceholderFragment (defined as a static inner class below).
            switch (position) {
                case 0:
                    return new inboxfragment();
                case 1:
                    return new Friendsfragment();
            }
            return null;
        }

        @Override
        public int getCount() {
            return 2;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            switch (position) {
                case 0:
                    return getString(R.string.title_section1).toUpperCase(l);
                case 1:
                    return getString(R.string.title_section2).toUpperCase(l);

            }
            return null;
        }
    }
}