ERROR: Android Runtime : FATAL EXCEPTION java.lang.RuntimeException
<p>I am getting this Error:</p>

<pre><code>05-09 23:34:04.251 21214-21214/com.example.averm.phonecontact E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.averm.phonecontact, PID: 21214
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.averm.phonecontact/com.example.averm.phonecontact.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int com.example.averm.phonecontact.DatabaseHandler.getContactsCount()' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2335)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2397)
    at android.app.ActivityThread.access$800(ActivityThread.java:151)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1310)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5268)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:902)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:697)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int com.example.averm.phonecontact.DatabaseHandler.getContactsCount()' on a null object reference
    at com.example.averm.phonecontact.MainActivity.onCreate(MainActivity.java:106)
    at android.app.Activity.performCreate(Activity.java:6033)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2288)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2397) 
    at android.app.ActivityThread.access$800(ActivityThread.java:151) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1310) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:135) 
    at android.app.ActivityThread.main(ActivityThread.java:5268) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:902) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:697)
</code></pre>

<p>My Code is:</p>

<p>MainActivity.java Class :</p>

<pre><code>public class MainActivity extends AppCompatActivity {

    private EditText nameTxt, phoneTxt, emailTxt, addressTxt;
    ImageView contactImageImgView;
    List&lt;Contact&gt; Contacts = new ArrayList&lt;Contact&gt;();
    ListView contactListView;
    Uri imageUri = Uri.parse("android.resource://org.intracode.contactmanager/drawable/no_user_logo.png");
    DatabaseHandler dbHandler;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        nameTxt = (EditText)findViewById(R.id.edName);
        phoneTxt = (EditText)findViewById(R.id.edNumber);
        emailTxt = (EditText)findViewById(R.id.edEmail);
        addressTxt = (EditText)findViewById(R.id.edAddress);
        contactListView = (ListView)findViewById(R.id.listView);
        contactImageImgView = (ImageView)findViewById(R.id.imgViewContactImage);


        TabHost tabHost = (TabHost)findViewById(R.id.tabHost);
        tabHost.setup();
        TabHost.TabSpec tabSpec = tabHost.newTabSpec("creator");
        tabSpec.setContent(R.id.tabCreator);
        tabSpec.setIndicator("Creator");
        tabHost.addTab(tabSpec);

        tabSpec = tabHost.newTabSpec("List");
        tabSpec.setContent(R.id.tabContactList);
        tabSpec.setIndicator("List");
        tabHost.addTab(tabSpec);


        final Button addBtn = (Button)findViewById(R.id.btnAdd);

        addBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Contact contact = new Contact(dbHandler.getContactsCount(), String.valueOf(nameTxt.getText()), String.valueOf(phoneTxt.getText()),
                        String.valueOf(emailTxt.getText()), String.valueOf(addressTxt.getText()), imageUri);
                if (!contactExists(contact)){
                    dbHandler.createContact(contact);
                    Contacts.add(contact);
                    Toast.makeText(getApplicationContext(),String.valueOf(nameTxt.getText()) +" has been added to your Contacts!", Toast.LENGTH_SHORT).show();
                    return;
                }
                Toast.makeText(getApplicationContext(), String.valueOf(nameTxt.getText()) + " already exists. Please use a different name.", Toast.LENGTH_SHORT).show();
            }
        });

        nameTxt.addTextChangedListener(new TextWatcher() {

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                addBtn.setEnabled(String.valueOf(nameTxt.getText()).trim().length() &gt; 0);
            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });

        contactImageImgView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent();
                intent.setType("image/*");
                intent.setAction(Intent.ACTION_GET_CONTENT);
                startActivityForResult(Intent.createChooser(intent, "Select Contact Image"), 1);
            }
        });

        if (dbHandler.getContactsCount() != 0)
            Contacts.addAll(dbHandler.getAllContacts());
        populateList();

    }

    public void onActivityResult(int reqCode, int resCode, Intent data){
        if (resCode == RESULT_OK){
            if (reqCode == 1){
                imageUri = data.getData();
                contactImageImgView.setImageURI(imageUri);
            }
        }
    }

    private boolean contactExists(Contact contact) {
        String name = contact.getName();
        int contactCount = Contacts.size();
        for (int i = 0; i &lt; contactCount; i++) {
            if (name.compareToIgnoreCase(Contacts.get(i).getName()) == 0)
                return true;
        }
        return false;
    }



    private void populateList(){
        ArrayAdapter&lt;Contact&gt; adaptor= new ContactListAdaptor();
        contactListView.setAdapter(adaptor);

    }


    private class ContactListAdaptor extends ArrayAdapter&lt;Contact&gt;{
        public ContactListAdaptor(){
            super(MainActivity.this,R.layout.listview_item, Contacts);
        }

        @Override
        public View getView(int position, View view, ViewGroup parent){
            if(view == null)
                view = getLayoutInflater().inflate(R.layout.listview_item, parent, false);

            Contact currentContact = Contacts.get(position);

            TextView name = (TextView) view.findViewById(R.id.contactName);
            name.setText(currentContact.getName());
            TextView phone = (TextView) view.findViewById(R.id.phoneNumber);
            phone.setText(currentContact.getPhone());
            TextView email = (TextView) view.findViewById(R.id.emailAddress);
            email.setText(currentContact.getEmail());
            TextView address = (TextView) view.findViewById(R.id.cAddress);
            address.setText(currentContact.getAddress());
            ImageView ivContactImage = (ImageView) view.findViewById(R.id.ivContactImage);
            ivContactImage.setImageURI(currentContact.getImageURI());
            return view;
        }
    }
}
</code></pre>

<p>DatabaseHandler.java Class:</p>

<pre><code>public class DatabaseHandler extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 2;
    private static final String DATABASE_NAME = "contactManager",
            TABLE_CONTACTS = "contacts",
            KEY_ID = "id",
            KEY_NAME = "name",
            KEY_PHONE = "phone",
            KEY_EMAIL = "email",
            KEY_ADDRESS = "address",
            KEY_IMAGEURI = "imageUri";

    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + TABLE_CONTACTS + "(" + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_NAME + " TEXT," + KEY_PHONE + " TEXT," + KEY_EMAIL + " TEXT," + KEY_ADDRESS + " TEXT," + KEY_IMAGEURI + " TEXT)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
        onCreate(db);
    }

    public void createContact(Contact contact) {
        SQLiteDatabase db = getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(KEY_NAME, contact.getName());
        values.put(KEY_PHONE, contact.getPhone());
        values.put(KEY_EMAIL, contact.getEmail());
        values.put(KEY_ADDRESS, contact.getAddress());
        values.put(KEY_IMAGEURI, contact.getImageURI().toString());
        db.insert(TABLE_CONTACTS, null, values);
        db.close();
    }

    public Contact getContact(int id) {
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID, KEY_NAME, KEY_PHONE, KEY_EMAIL, KEY_ADDRESS, KEY_IMAGEURI }, KEY_ID + "=?", new String[] { String.valueOf(id) }, null, null, null, null );
        if (cursor != null)
            cursor.moveToFirst();
        Contact contact = new Contact(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4), Uri.parse(cursor.getString(5)));
        db.close();
        cursor.close();
        return contact;
    }



    public int getContactsCount() {
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_CONTACTS, null);
        int count = cursor.getCount();
        db.close();
        cursor.close();
        return count;
    }
}
</code></pre>