public class GlobalApp extends Application{


    @Override
    public void onCreate() {
        super.onCreate();

    DatabaseHelper databaseHelper = new DatabaseHelper(getApplicationContext());
    MySingleton.init(databaseHelper);

    }
}

public class MySingleton{

   static MySingleton instance;
   DatabaseHelper databaseHelper;

   public static void init(DatabaseHelper databaseHelper){
      instance = new MySingleton(databaseHelper);
   }

}

<application
        android:name=".application.DoodhwaalaApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

public class SingletonModel {
 private static SingletonModel instance;
 public DatabaseHelper databaseHelper;


 public synchronized  static SingletonModel getSingletonModel() {

     if (instance == null) {
         instance = new SingletonModel();
     }
     return instance;

 }

 private void SingletonModel(){}

 }

public class AddEventModel {

            private String event_name;
            private String event_image;
            private static AddEventModel _instance;

        //For Single Ton

        public static AddEventModel get_instance() {
                return _instance;
            }

            public static AddEventModel getInstance() {
                if (_instance == null) {
                    _instance = new AddEventModel();
                }
                return _instance;
            }
         public static void set_instance(AddEventModel _instance) {
                AddEventModel._instance = _instance;
            }

        //Getter setter for model.
            public String getEvent_image() {
                return event_image;
            }

            public void setEvent_image(String event_image) {
                this.event_image = event_image;
            }

            public String getEvent_name() {
                return event_name;
            }

            public void setEvent_name(String event_name) {
                this.event_name = event_name;
            }

edtEventName.addTextChangedListener(new TextWatcher() {

                    @Override
                    public void onTextChanged(CharSequence s, int start, int before, int count) {
    //Save edit text value in single ton instance.
                AddEventModel.getInstance().setEvent_name(edtEventName.getText().toString().trim());
                    }

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

                    @Override
                    public void afterTextChanged(Editable s) {

                    }
                });

@Override
            public void onResume() {
                super.onResume();

        // Set same value saved in single ton before in onResume.
        edtEventName.setText(AddEventModel.getInstance().getEvent_name());

        }

public class MySingleton {

    static MySingleton instance;

    DatabaseHelper databaseHelper;

    public/private MySingleton(DatabaseHelper databaseHelper) {
        // TODO Auto-generated constructor stub
    }

    public static void init(DatabaseHelper databaseHelper) {
        instance = new MySingleton(databaseHelper);
    }
}

instance = new MySingleton(databaseHelper);

instance = MySingleton.getInstance(databaseHelper);

public class MySingleton {

    public static final MySingleton singleton = new MySingleton(DatabaseHelper databaseHelper);
    DatabaseHelper databaseHelper=  null;

    private MySingleton(DatabaseHelper databaseHelper) {
        this.databaseHelper = databaseHelper;
    }

    public MySingleton getInstance() {
        return singleton;
    }
}