如何在没有用户注册的情况下进入Firebase应用

Question

我希望用户无需注册即可使用该应用程序。但是，当用户想要进行某些活动时，应该注册该用户。

这是我的注册和登录活动：

public class RegisterActivity extends AppCompatActivity {

    EditText username, fullname, email, password;
    Button register;
    TextView login;

    FirebaseAuth auth;
    DatabaseReference reference;
    ProgressDialog progressDialog;

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

        username = findViewById(R.id.username);
        email = findViewById(R.id.email);
        fullname = findViewById(R.id.fullname);
        password = findViewById(R.id.password);
        register = findViewById(R.id.register);
        login = findViewById(R.id.login);

        auth = FirebaseAuth.getInstance();

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(RegisterActivity.this, LoginActivity.class));
            }
        });

        register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                progressDialog = new ProgressDialog(RegisterActivity.this);
                progressDialog.setMessage("wait");
                progressDialog.show();

                String str_username = username.getText().toString();
                String str_fullname = fullname.getText().toString();
                String str_email = email.getText().toString();
                String str_password = password.getText().toString();

                if (TextUtils.isEmpty(str_username) || TextUtils.isEmpty(str_fullname) || TextUtils.isEmpty(str_email) || TextUtils.isEmpty(str_password)){
                    Toast.makeText(RegisterActivity.this, "", Toast.LENGTH_SHORT).show();
                } else if(str_password.length() < 4){
                    Toast.makeText(RegisterActivity.this, "", Toast.LENGTH_SHORT).show();
                } else {
                    register(str_username, str_fullname, str_email, str_password);
                }
            }
        });
    }

    public void register(final String username, final String fullname, String email, String password){
        auth.createUserWithEmailAndPassword(email, password)
                .addOnCompleteListener(RegisterActivity.this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()){
                            FirebaseUser firebaseUser = auth.getCurrentUser();
                            String userID = firebaseUser.getUid();

                            reference = FirebaseDatabase.getInstance().getReference().child("Users").child(userID);
                            HashMap<String, Object> map = new HashMap<>();
                            map.put("id", userID);
                            map.put("username", username.toLowerCase());
                            map.put("fullname", fullname);
                            map.put("imageurl" );


                            reference.setValue(map).addOnCompleteListener(new OnCompleteListener<Void>() {
                                @Override
                                public void onComplete(@NonNull Task<Void> task) {
                                    if (task.isSuccessful()){
                                        progressDialog.dismiss();
                                        Intent intent = new Intent(RegisterActivity.this, MainActivity.class);
                                        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
                                        startActivity(intent);
                                    }
                                }
                            });
                        } else {
                            progressDialog.dismiss();
                            Toast.makeText(RegisterActivity.this, "", Toast.LENGTH_SHORT).show();
                        }
                    }
                });

        auth.signInWithEmailAndPassword(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

                            FirebaseUser user = auth.getCurrentUser();

                        } else {
                            // If sign in fails, display a message to the user.

                            Toast.makeText(RegisterActivity.this, "failed",
                                    Toast.LENGTH_SHORT).show();
                        }

                    }
                });
    }
}

public class LoginActivity extends AppCompatActivity {

    EditText email, password;
    Button login;
    TextView signup;

    FirebaseAuth auth;

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

        email = findViewById(R.id.email);
        password = findViewById(R.id.password);
        login = findViewById(R.id.login);
        signup = findViewById(R.id.signup);

        auth = FirebaseAuth.getInstance();

        signup.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(LoginActivity.this, RegisterActivity.class));
            }
        });

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                final ProgressDialog progressDialog = new ProgressDialog(LoginActivity.this);
                progressDialog.setMessage("wait");
                progressDialog.show();

                String str_email = email.getText().toString();
                String str_password = password.getText().toString();

                if (TextUtils.isEmpty(str_email) || TextUtils.isEmpty(str_password)){
                    Toast.makeText(LoginActivity.this, "", Toast.LENGTH_SHORT).show();
                } else {

                    auth.signInWithEmailAndPassword(str_email, str_password)
                            .addOnCompleteListener(LoginActivity.this, new OnCompleteListener<AuthResult>() {
                                @Override
                                public void onComplete(@NonNull Task<AuthResult> task) {
                                    if (task.isSuccessful()) {

                                        DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Users")
                                                .child(auth.getCurrentUser().getUid());

                                        reference.addValueEventListener(new ValueEventListener() {
                                            @Override
                                            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                                                progressDialog.dismiss();
                                                Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                                                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
                                                startActivity(intent);
                                                finish();
                                            }

                                            @Override
                                            public void onCancelled(@NonNull DatabaseError databaseError) {
                                                progressDialog.dismiss();
                                            }
                                        });
                                    } else {
                                        progressDialog.dismiss();
                                        Toast.makeText(LoginActivity.this, "failed.", Toast.LENGTH_SHORT).show();
                                    }
                                }
                            });
                }
            }
        });
    }
}