Android MVP空对象参考

Question

I am trying to do the MvP Pattern and I am separating firebase queries in the model part. I get null object reference exception when I call it on the presenter.

Model:

public class LoginModelz  implements LoginContract.LoginModelz {
    private LoginPresenter loginPresenter;

    FirebaseAuth mAuth; //= FirebaseAuth.getInstance();
    FirebaseUser currentuser;// = mAuth.getCurrentUser();


    public LoginModelz(LoginPresenter loginPresenter) {
        this.loginPresenter = loginPresenter;
    }
    public void FirebaseQuery(){
        mAuth = FirebaseAuth.getInstance();
        currentuser = mAuth.getCurrentUser();

    }

}

Presenter:

public class LoginPresenter implements LoginContract.LoginPresenter {
      private LoginView loginView;
     private LoginModelz loginModelz;

    public LoginPresenter(LoginView loginView) {
        this.loginView = loginView;
    }

    public LoginPresenter(LoginModelz loginModelz) {
        this.loginModelz = loginModelz;
    }

    @Override
    public void OnLogin(String email, String password,final Context context) {
      loginModelz.FirebaseQuery();
        Log.e("asda",context.toString());
        if(email.isEmpty() && password.isEmpty()){
            loginView.OnLoginFail("Email and Password is empty");
            return;
        }
        else if(email.isEmpty()){
            loginView.OnLoginFail("Email is empty");
            return;
        }else if(password.isEmpty()){
            loginView.OnLoginFail("Password is empty");
            return;
        }else {
           loginView.ProgressShow("ASDASDASDASDSAd");
           Log.e("emailpass", email+password);
            **loginModelz.mAuth.signInWithEmailAndPassword(email,password)**
                    .addOnCompleteListener( new OnCompleteListener<AuthResult>() 

I was getting an error from the loginmodelz.mAuth . If i put the initializations in the method in the presenter class it works just fine, but when i separated it is getting a null object reference.

Interfaces

 public interface LoginContract {
  interface LoginView{
   void OnLoginSuccess();
   void OnLoginFail(String message);
   void Onregister();
   void ProgressShow(String messsagge);
   void ProgressDismiss(String message);
   void Alert();

}
interface LoginPresenter{
  void OnLogin(String email,String password,final Context context);
  void OnVerify(Context context);

}
 interface LoginModelz{
    void FirebaseQuery();
 }

  }

Answer 1

This looks suspicious:

public LoginPresenter(LoginView loginView) {
  this.loginView = loginView;
}

public LoginPresenter(LoginModelz loginModelz) {
  this.loginModelz = loginModelz;
}

You have to decide on your constructor, if you call the first one you don't have a model and so on.

You could create your model inside the first constructor and pass it as an argument:

public LoginPresenter(LoginView loginView) {
      this.loginView = loginView;
      this.loginModel = new LoginModel(this);
}

At least that's what I can suggest from the code you provided.

Answer 2

You have not initialized loginModelz. Change your presenter constructor implement

public LoginPresenter(LoginView loginView) {
    this.loginView = loginView;
    this.loginModelz = new LoginModelz(this);
}