Getting null in return when calling model class getter methods in second activity-CodePudding

First I initialized a model class all attributes value in first activity by calling its constructor like this UserName userName=new UserName("UnknownPerson","7dfgdufdbid_bjd"); but when I'm calling the getter methods of this model class in second activity it returning null.How to get that values in second activity without intent.putExtra().Look at my Code:


public class UserName {
    String name,userId;
    public UserName(String name, String userId) {
        this.name = name;
        this.userId = userId;
    }
    public UserName() {
    }
    public String getName() {
        return name;
    }
    public String getUserId() {
        return userId;
    }
}

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        UserName userName=new UserName("UnknownPerson","7dfgdufdbid_bjd");
        Log.d("Test",userName.getName() " " userName.getUserId());
        findViewById(R.id.button).setOnClickListener(v -> {
            startActivity(new Intent(this,MainActivity2.class));
        });
    }
}

public class MainActivity2 extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        UserName userName=new UserName();
        Log.d("Test",userName.getName() " " userName.getUserId());
    }
}

CodePudding user response：

It is correct to return null, if you want to get the object of the first page on the second page, you should serialize UserName first. Then call a function like the following on the first page：

Intent i = new Intent(MainActivity.this, MainActivity2.class);
i.putExtra(key, value);
startActivity(i)

On the second page, use getIntent().getExtras().getParcelable(key) to get the serialized object passed from the first page，In Android we generally use Parcelable for serialization

CodePudding user response：

you are creating new object in MainActivity2 that's why it is returning null. you should pass data in bundle.

 public Bundle toBundle(UserName username) {
            Bundle b = new Bundle();
            b.putString("userid",username.id);
            b.putString("username", username.name);
          
            return b;
        }

public class MainActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    UserName userName=new UserName("UnknownPerson","abc");
    Log.d("Test",userName.getName() " " userName.getUserId());
    Intent intent = Intent(this, MainActivity2.class);
    intent.putExtras(toBundle(username))
    findViewById(R.id.button).setOnClickListener(v -> {
        startActivity(intent);
    });
}

}

 public class MainActivity2{
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main2);
            Bundle b = this.getIntent().getExtras();
            Log.d("Test",userName.getName() " " b.getString("username"));
            Log.d("Test",userName.getId() " " b.getString("userid"));
        }
    }

hope it works!!