Firebase登录卡顿+NullPointerException+GmsCore错误求助（Java新手）

问题概述 #

• 点击登录按钮后，页面一直显示「Please waiting」弹窗，无法跳转至首页，同时触发NullPointerException；
• 出现「Invalid GmsCore APK」提示：远程加载已禁用，缺少Google Play Store，Firebase对象访问触发空指针异常。

相关资源 #

Realtime Database截图 #

SignIn页面代码 #

package com.example.eatit_new;

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;

import com.example.eatit_new.Common.Common;
import com.example.eatit_new.Model.User;
import com.google.android.material.snackbar.Snackbar;

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

import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;

import com.example.eatit_new.databinding.ActivitySignInBinding;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.rengwuxian.materialedittext.MaterialEditText;

public class SignIn extends AppCompatActivity {
    EditText editPhone, editPassword;
    Button btnSignIn;
@Override
    protected void onCreate (Bundle saveInstanceState) {
        super.onCreate(saveInstanceState);
        setContentView(R.layout.activity_sign_in);

        editPassword=(MaterialEditText)findViewById(R.id.editPassword);

        editPhone= (MaterialEditText)findViewById(R.id.editPhone);
        btnSignIn = (Button) findViewById(R.id.btnSignIn);

    //init Database
    final FirebaseDatabase database= FirebaseDatabase.getInstance();
    final DatabaseReference table_user=database.getReference("User");

btnSignIn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {

        final ProgressDialog mDialog = new ProgressDialog(SignIn.this);
        mDialog.setMessage("Please waiting....");
        mDialog.show();

        table_user.addValueEventListener( new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                //Check if user not exist in database

                if (dataSnapshot.child(editPhone.getText().toString()).exists()) {

                    //Get User Information
                    mDialog.dismiss();
                    User user = dataSnapshot.child(editPhone.getText().toString()).getValue(User.class);
                    if (user.getPassword().equals(editPassword.getText().toString())) {

                        Intent homeIntent= new Intent(SignIn.this,Home.class);
                        Common.currentUser= user;
                        startActivity(homeIntent);
                        finish();
                    } else {
                        Toast.makeText(SignIn.this, "Wrong password!", Toast.LENGTH_SHORT).show();
                    }
                } else {
                    mDialog.dismiss();
                    Toast.makeText(SignIn.this, "User not exists!", Toast.LENGTH_SHORT).show();
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }
});
}
}

User类代码 #

package com.example.eatit_new.Model;

public class User {
    String name;
    String password;

    public User() {
    }

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}

public User(String name, String password) {
    this.name = name;
    this.password = password;
}
}

附加截图 #

报错截图 #

解决方案 #

一、解决「Invalid GmsCore APK」与Firebase空指针问题 #

Firebase依赖Google Play Services运行，该提示说明测试设备缺少相关服务：

1. 若使用模拟器：创建带Google Play服务的镜像（选择「Google APIs」或「Google Play」类型的系统镜像），不要使用纯Android原生镜像；
2. 若使用真机：确保设备安装了Google Play Store，且Google Play Services为最新版本；
3. 检查项目依赖：确认Module级build.gradle中添加了必要依赖，同步后重新运行：

   implementation 'com.google.firebase:firebase-database:20.3.0'
   implementation 'com.google.android.gms:play-services-base:18.2.0'
   

二、解决弹窗持续显示+NullPointerException问题 #

空指针大概率因user对象为空、输入框文本为空，或未处理数据库请求失败导致，按以下步骤修改：

1. 添加空值校验：在获取用户数据前校验输入合法性，获取后校验对象不为空：
   修改onDataChange方法：

   @Override
   public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
       String phone = editPhone.getText().toString().trim();
       String password = editPassword.getText().toString().trim();
   
       if (phone.isEmpty() || password.isEmpty()) {
           mDialog.dismiss();
           Toast.makeText(SignIn.this, "请输入手机号和密码", Toast.LENGTH_SHORT).show();
           return;
       }
   
       if (dataSnapshot.child(phone).exists()) {
           mDialog.dismiss();
           User user = dataSnapshot.child(phone).getValue(User.class);
           if (user != null) {
               if (user.getPassword().equals(password)) {
                   Intent homeIntent= new Intent(SignIn.this,Home.class);
                   Common.currentUser= user;
                   startActivity(homeIntent);
                   finish();
               } else {
                   Toast.makeText(SignIn.this, "密码错误！", Toast.LENGTH_SHORT).show();
               }
           } else {
               Toast.makeText(SignIn.this, "用户数据加载失败", Toast.LENGTH_SHORT).show();
           }
       } else {
           mDialog.dismiss();
           Toast.makeText(SignIn.this, "用户不存在！", Toast.LENGTH_SHORT).show();
       }
   }
   

2. 处理onCancelled回调：数据库请求失败时关闭弹窗并提示，避免弹窗一直显示：

   @Override
   public void onCancelled(@NonNull DatabaseError databaseError) {
       mDialog.dismiss();
       Toast.makeText(SignIn.this, "数据库请求失败：" + databaseError.getMessage(), Toast.LENGTH_SHORT).show();
   }
   

3. 改用单次数据监听：登录只需一次性获取数据，替换addValueEventListener为addListenerForSingleValueEvent，避免不必要的持续监听：

   table_user.addListenerForSingleValueEvent(new ValueEventListener() {
       // 内部方法同上修改
   });
   

内容的提问来源于stack exchange，提问作者Đoàn Thanh Thảo