No setter/field for ( ) found on my class

Question

I tried to make a login screen for my application, but when I enter the right Id and password that should work my application keeps stopping. Furthermore, When I debug the codes, error messages such as:

 W/ClassMapper: No setter/field for User found on class com.example.(Projectname).User
 No setter/field for BookReport found on class com.example.(Projectname).User

 E/AndroidRuntime: FATAL EXCEPTION: main
 Process: com.example.(Projectname), PID: 3339
 java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
    at com.example.(Projectname).LoginScreen$1$1.onDataChange(LoginScreen.java:79)

Comes out. Why does it happen?

Obviously `userId` or `userPw` is null, whichever line 79 is. Which part of the error message confuses you? Perhaps if you add null check, e.g. `if (userId != null && userId.equals(id))`, the code wouldn't fail. — Andreas, Aug 28 '19 at 18:47
Duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/q/218384/5221149) — Andreas, Aug 28 '19 at 18:48

score 1 · Answer 1 · answered Aug 28 '19 at 18:47

1

It seems that the com.example.hellobook.User class does not define setters for its fields. Try defining a setter for all the fields so the statement foundUser = dataSnapshot.getValue(User.class); can create a correct User object

e.g.

public void setBookReport(BookReport bookReport){
    this.bookReport = bookReport;
}

answered Aug 28 '19 at 18:47

Maher Malaeb

321
2
5

1

Well, nothing can be said, unless the OP posts the `User` class. – Gaurav Mall Aug 29 '19 at 07:39

score -1 · Answer 2 · answered Aug 28 '19 at 18:59

sir your error is this line if (userId.equals(id)) becuase you set the value of dataSnapShot in foundUser Object outside the for loop.

    ref.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        for (DataSnapshot ds : dataSnapshot.getChildren()) {
                            foundUser = dataSnapshot.getValue(User.class);
                            userId = foundUser.getId();
                            userPw = foundUser.getPw();
                            if (userId.equals(id)) {
                                if (userPw.equals(psw)) {
                                    startActivity(new Intent(LoginScreen.this, LandingScreen.class));
                                }

                            }
                            else {
                                Toast.makeText(LoginScreen.this, "Wrong ID or password. Try again", Toast.LENGTH_SHORT).show();
                            }

                        }
                    }
                    @Override
                    public void onCancelled (DatabaseError error) {
                        @NonNull DatabaseError databaseError;                        }
                });
            };

Your answer sounded very reasonable and I tried it, but still I cannot solve the problem :(( — purplecherry, Aug 29 '19 at 11:19
does it shows the same error. do you check the log value of user id or debug it. is it null or not before the if check — Hasnain Sabir, Aug 29 '19 at 15:29

No setter/field for ( ) found on my class

2 Answers2