如何从 Firebase 实时数据库中检索用户用户名以获取欢迎回复消息?

Question

我有一个安卓工作室项目，用户使用电子邮件地址和密码登录。用户的用户名在注册时会存储在Firebase的实时数据库中。 如何从数据库中检索用户名，以便在成功登录后显示欢迎返回(用户名(消息？

我已经附加了主屏幕java，这是我希望消息出现的地方。 我还附加了登录 java，用户可以在其中输入他们的电子邮件和密码。 用户在其中输入其详细信息和用户类的注册类。

提前感谢，我对代码很陌生，所以请原谅我的无知。

package com.example.securityapp;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import com.google.firebase.auth.FirebaseAuth;
public class home extends AppCompatActivity {
Button training;
Button signOut;
Button loginPage;
private FirebaseAuth mAuth;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
training = (Button) findViewById(R.id.training_button);
signOut = (Button) findViewById(R.id.sign_out);
mAuth = FirebaseAuth.getInstance();
FirebaseAuth mAuth;
}

public void signOutUser() {
mAuth.signOut();
Toast.makeText(home.this, "Sign out successful!", Toast.LENGTH_LONG).show();
Intent intent_signout = new Intent(home.this, login.class);
startActivity(intent_signout);
finish();
}
public void SignoutOnClick(View view) {
signOut.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
signOutUser();
}
});
}
public void TrainingOnClick(View view) {
training.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent_training = new Intent(home.this, training.class);
startActivity(intent_training);
finish();
}
});
}
public void loginOnClick (View view){
loginPage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent_login = new Intent(home.this, register.class);
startActivity(intent_login);
finish();
}
});
}
}

package com.example.securityapp;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
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;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
public class register extends AppCompatActivity {
private FirebaseAuth mAuth;
EditText emailReg, passwordReg, password2, roleReg, officeReg;
Button regButton;
DatabaseReference databaseUsers;
EditText usernameReg;
FirebaseDatabase database = FirebaseDatabase.getInstance();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
emailReg = (EditText) findViewById(R.id.regEmail);
usernameReg = (EditText) findViewById(R.id.regUsername);
passwordReg = (EditText) findViewById(R.id.regPassword);
regButton = (Button) findViewById(R.id.register_Button);
password2 = (EditText) findViewById(R.id.confirm_password);
roleReg = (EditText) findViewById(R.id.regRole);
officeReg = (EditText) findViewById(R.id.regOffice);
databaseUsers = database.getReference();
mAuth = FirebaseAuth.getInstance();
}
public void registerUser() {
final String email = emailReg.getText().toString();
final String password = passwordReg.getText().toString();
String pass2 = password2.getText().toString();
if(!pass2.equals(password))
{
Toast.makeText(register.this, "Passwords Do Not Match",
Toast.LENGTH_SHORT).show();
return;
}
//Code taken from https://firebase.google.com/docs/auth/android/start on 10/11/2019
mAuth.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
// Sign in success, update UI with the signed-in user's information
insertDataDB();
Intent intent_signup = new Intent(register.this, home.class);
startActivity(intent_signup);
finish();
FirebaseUser user = mAuth.getCurrentUser();
Toast.makeText(register.this, "Authentication Successful!",
Toast.LENGTH_SHORT).show();
} else {
// If sign in fails, display a message to the user.
Toast.makeText(register.this, "Authentication failed.",
Toast.LENGTH_SHORT).show();
}
// ...
}
});
}
public void registerOnClick(View view)
{
regButton.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
registerUser();
}
});
}
public void insertDataDB()
{
String username = usernameReg.getText().toString();
String job = roleReg.getText().toString();
String email = emailReg.getText().toString();
String office = officeReg.getText().toString();
String id = databaseUsers.push().getKey();
Users user1 = new Users(username, job, email, office);
databaseUsers.child(id).setValue(user1);
}
}

package com.example.securityapp;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
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
//implements View.OnClickListener
{
Button signUp;
Button login;
EditText etEmail;
EditText etPassword;
ProgressBar bar;
FirebaseAuth mAuth;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
signUp = (Button) findViewById(R.id.signUp_button);
login = (Button) findViewById(R.id.login_button);
etEmail = (EditText)findViewById(R.id.email_input);
etPassword = (EditText)findViewById(R.id.password_input);
bar = (ProgressBar) findViewById(R.id.progressBar);
bar.setVisibility(View.GONE);
mAuth = FirebaseAuth.getInstance();
}
@Override
public void onStart()
{
super.onStart();
// Check if user is signed in (non-null) and update UI accordingly.
FirebaseUser currentUser = mAuth.getCurrentUser();
}
//Code taken from https://firebase.google.com/docs/auth/android/password-auth on 06/11/2019
public void loginUser()
{
final String email = etEmail.getText().toString();
String password = etPassword.getText().toString();
if(email.isEmpty()&&password.isEmpty())
{
Toast.makeText(login.this, "Email and password cannot be empty.",
Toast.LENGTH_SHORT).show();
bar.setVisibility(View.GONE);
}else if(email.isEmpty())
{
Toast.makeText(login.this, "Email cannot be empty.",
Toast.LENGTH_SHORT).show();
bar.setVisibility(View.GONE);
}else if(password.isEmpty())
{
Toast.makeText(login.this, "Password cannot be empty.",
Toast.LENGTH_SHORT).show();
bar.setVisibility(View.GONE);
}else
mAuth.signInWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful())
{
//Log.d(TAG, "signInWithEmail:success");
// FirebaseUser user = mAuth.getCurrentUser();
bar.setVisibility(View.VISIBLE);
Intent intent_home = new Intent(login.this, home.class);
startActivity(intent_home);
finish();
Toast.makeText(login.this, "Login successful",
Toast.LENGTH_SHORT).show();
//updateUI(user);
} else {
// If sign in fails, display a message to the user.
//Log.w(TAG, "signInWithEmail:failure", task.getException());
Toast.makeText(login.this, "Incorrect Email or Password.",
Toast.LENGTH_SHORT).show();
bar.setVisibility(View.GONE);
//updateUI(null);
}
// ...
}
});
}

public void loginOnClick (View view)
{
login.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
bar.setVisibility(View.VISIBLE);
loginUser();
}
});
}
public void RegisterOnClick (View view)
{
signUp.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
Intent intent_reg = new Intent(login.this, register.class);
startActivity(intent_reg);
finish();
}
});
}
}

package com.example.securityapp;
public class Users {
String username;
String job;
String email;
String office;
public Users() {
}
public Users(String username, String job, String email, String office) {
this.username = username;
this.job = job;
this.email = email;
this.office = office;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getOffice() {
return office;
}
public void setOffice(String office) {
this.office = office;
}
}

Answer 1

试试这个...

FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
if (user != null) {
String name = user.getDisplayName();
String email = user.getEmail();
Uri photoUrl = user.getPhotoUrl();
// User is signed in
} else {
// No user is signed in
}

遵循 Firebase 文档

Answer 2

看看这个方法：

mAuth.signInWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
Log.d(TAG, "signInWithEmail:success");
FirebaseUser user = mAuth.getCurrentUser();
// Do something here...
} else {
// If sign in fails, display a message to the user..
}
}
});

登录时，输入方法"完成"，您可以使用

FirebaseUser user = mAuth.getCurrentUser((

为了获取您想要的有关用户的任何信息，例如电子邮件，姓名等。