java - firebase 用户在第一次调用后每次都会返回 null

Question

首次调用此 (user = firebaseAuth.getCurrentUser();) 后，Firebase 用户返回 null。

首次安装应用程序时，firebaseAuth.getCurrentUser() 返回用户，但当它从第一个 Activity 移动到另一个 Activity 时，之后会调用“sigh Out”按钮firebaseAuth.getCurrentUser() 每次都返回 null。

package com.example.firebaselogin;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;

public class logIn extends AppCompatActivity {

    EditText userName, pwd;
    TextView signUpHere;
    Button loginButton;
    private FirebaseAuth firebaseAuth;
    //private FirebaseAuth.AuthStateListener listener;

    ProgressDialog progressDialog;
    FirebaseUser user;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_log_in);

        firebaseAuth = FirebaseAuth.getInstance();
        progressDialog = new ProgressDialog(this);

        user = firebaseAuth.getCurrentUser();

        userName = findViewById(R.id.userName);
        pwd = findViewById(R.id.pwd);
        signUpHere = findViewById(R.id.signUpHere);
        loginButton = findViewById(R.id.loginButton);

        loginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                progressDialog.setMessage("Please Wait");
                progressDialog.show();

                Log.i("Userrrr", String.valueOf(user));

                if(validate()) {
                    if (user != null) {
                        firebaseAuth.signInWithEmailAndPassword(userName.getText().toString().trim(), pwd.getText().toString().trim()).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                            @Override
                            public void onComplete(@NonNull Task<AuthResult> task) {
                                if (task.isSuccessful()) {
                                    Intent intent = new Intent(logIn.this, WelcomePage.class);
                                    startActivity(intent);
                                    Toast.makeText(getApplicationContext(), "Successful", Toast.LENGTH_SHORT).show();
                                    progressDialog.dismiss();
                                } else {
                                    Toast.makeText(getApplicationContext(), "Failed", Toast.LENGTH_SHORT).show();
                                    progressDialog.dismiss();
                                }
                            }
                        });
                    } else {
                        Toast.makeText(getApplicationContext(), "Failed", Toast.LENGTH_SHORT).show();
                        progressDialog.dismiss();
                    }
                }
            }
        });

        signUpHere.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getApplicationContext(), MainActivity.class);
                startActivity(intent);
            }
        });

    }

    private Boolean validate() {

        Boolean result = false;

        String name = userName.getText().toString();
        String password = pwd.getText().toString();

        if(name.isEmpty() || password.isEmpty()) {
            Toast.makeText(getApplicationContext(), "Enter all details", Toast.LENGTH_SHORT).show();
        } else {
            result = true;
        }

        return result;

    }

}

当第一次调用firebaseAuth.getCurrentUser()时，它是

returning (2019-08-29 00:08:14.561 8165-8165/com.example.firebaselogin I/Userrrr: com.google.firebase.auth.internal.zzk@44ffb65) but after the signOut is triggered from a next activity, firebaseAuth.getCurrentUser() is returning null everytime 2019-08-29 00:08:24.651 8165-8165/com.example.firebaselogin I/Userrrr: null``

Answer 1

正如我所看到的，您在签署用户之前检查用户是否为空。因此，当用户注销并尝试再次登录时，现在该用户为空。根据你的情况，如果用户不为空，则全部登录，否则不登录。由于用户为空，总是失败，用户无法登录。删除该条件，您就可以开始了。