访问已创建的相同类Android对象

Question

So I am creating a chat app for android and I'm using Java and I need some help wrapping my head around some things. Whenever the user first registers, I am creating a new object of a class named User. When they enter the next layout, I need to access that objects data.

public class User {
public String username;
public User() {}

public User(String username) {
    this.username = username;
}

public String getUsername(){
    return username;
  }
}

This is my User class. When they send a message, I need to be able to grab their username from this User object from an entirely different method without passing the object through a parameter. I can't seem to wrap my head around how to access their information and none of my methods seem to work. Any help is appreciated

Answer 1

If you do

User myUser = new User();

the variable myUser contains a reference to the newly created object. You must keep this reference around in order to later access the object. How exactly you do this depends on the logic of your program. Sometimes you would keep it in a field of another object or pass it around as parameter. For example

un = myUser.getUsername();

or

void myMethod(User theUser) {
    ...
    String un = theUser.getUsername();
}

...

// call the method passing the user reference
myMethod(myUser);

Answer 2

in the main class make the data object... static

public static Model obj; obj= new Model(); then from other class access it with your class name

example main.obj;

Answer 3

I solved this issue by just using SharedPreferences. I stored the username associated with the key of each user. This way, I can always search the username for each user.