添加 Firebase 身份驗證后，在 Android Studio（登錄活動）中使用 SharedPreferences() 方法時出錯

Question

我的代碼一直有效，直到我將 Firebase 添加到它。 這是我的登錄頁面，SharedPreferences 不起作用。 當我點擊登錄按鈕時，密碼作為用戶名和密碼彈出 - 然后當我重新運行模擬器時 - 用戶名和密碼為 null。 請幫我找出錯誤：

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

import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
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;

public class Login extends AppCompatActivity {
    EditText username;
    EditText etPassword;
    Button loginBtn;
    Button registerBtn;
    private SharedPreferences mPreferences;
    private SharedPreferences.Editor mEditor;
    private static String TAG = "Michael's Tracking --> ";
    private FirebaseAuth mAuth;

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

        Log.d(TAG, "Start onCreate");

        username = findViewById(R.id.username);
        etPassword = findViewById(R.id.etPassword);
        loginBtn = findViewById(R.id.registerBtn);
        registerBtn = findViewById(R.id.toLoginBtn);

        mPreferences = PreferenceManager.getDefaultSharedPreferences(this);
        mEditor = mPreferences.edit();

        mAuth = FirebaseAuth.getInstance();

            super.onStart();
            // Check if user is signed in (non-null) and update UI accordingly.
            FirebaseUser currentUser = mAuth.getCurrentUser();
            if(currentUser != null){
                currentUser.reload();
            }

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

                String email = username.getText().toString();
                String pass = etPassword.getText().toString();

                String stName = email;
                mEditor.putString(getString(R.string.name), stName);
                mEditor.commit();

                String stPassword = pass;
                mEditor.putString(getString(R.string.password), stPassword);
                mEditor.commit();

                checkSharedPreferences();

                mAuth.signInWithEmailAndPassword(email, pass)
                        .addOnCompleteListener(Login.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
                                    Log.d(TAG, "signInWithEmail:success");
                                    FirebaseUser user = mAuth.getCurrentUser();
                                    startActivity(new Intent(Login.this, MainPage.class));
                                } else {
                                    // If sign in fails, display a message to the user.
                                    Log.w(TAG, "signInWithEmail:failure", task.getException());
                                    Toast.makeText(Login.this, "Authentication failed.",
                                            Toast.LENGTH_SHORT).show();
                                }
                            }
                        });
            }
        });

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

                Intent registerPage = new Intent(Login.this, Register.class);
                startActivity(registerPage);

            }
        });
    }

    private void checkSharedPreferences() {
        String stName, stPassword;
        stName = mPreferences.getString(getString(R.string.name), "");
        stPassword = mPreferences.getString(getString(R.string.password), "");
        username.setText(stName);
        etPassword.setText(stPassword);
    }

}```

Thank you very much!

Answer 1

checkSharedPreferences()方法不應在onClick內部調用，它用於恢復數據，因此應在開始時調用它，因此在onCreate引用View s（ findViewById ）和首選項（ mPreferences ， mEditor ）之后

Answer 2

成功登錄后使用共享首選項存儲用戶名和密碼。

      mAuth.signInWithEmailAndPassword(email, pass)
                        .addOnCompleteListener(Login.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
                                            Log.d(TAG, "signInWithEmail:success");
                                            FirebaseUser user = mAuth.getCurrentUser();
                                            mEditor.putString("Useranme", stName);

                                            mEditor.putString("Password", stPassword);
                                                    mEditor.commit();
                                            startActivity(new Intent(Login.this, MainPage.class));
                                        } else {
                                            // If sign in fails, display a message to the user.
                                            Log.w(TAG, "signInWithEmail:failure", task.getException());
                                            Toast.makeText(Login.this, "Authentication failed.",
                                                    Toast.LENGTH_SHORT).show();
                                        }
                                    }
                                });
            }
        });