帮我写个android的登陆注册页面，使用sqlite数据库

好的，下面是一个简单的 Android 登录注册页面的示例，使用 SQLite 数据库进行用户信息的保存和验证。

首先，在 Android Studio 中创建一个新项目，并添加以下依赖项到 app/build.gradle 文件中：

dependencies {
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'androidx.recyclerview:recyclerview:1.1.0'
    implementation 'androidx.cardview:cardview:1.0.0'
    implementation 'androidx.sqlite:sqlite:2.0.1'
}

接下来，在 res/layout 文件夹中创建两个布局文件：activity_login.xml 和 activity_register.xml。这些布局文件将包含登录和注册表单。

activity_login.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <EditText
        android:id="@+id/edit_email"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Email"/>

    <EditText
        android:id="@+id/edit_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Password"
        android:inputType="textPassword"/>

    <Button
        android:id="@+id/btn_login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Login"/>

    <TextView
        android:id="@+id/txt_register"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Don't have an account? Register here."/>

</LinearLayout>

activity_register.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <EditText
        android:id="@+id/edit_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Name"/>

    <EditText
        android:id="@+id/edit_email"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Email"/>

    <EditText
        android:id="@+id/edit_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Password"
        android:inputType="textPassword"/>

    <Button
        android:id="@+id/btn_register"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Register"/>

</LinearLayout>

接下来，创建一个名为 DatabaseHelper 的帮助程序类，该类将处理 SQLite 数据库的创建和版本控制：

public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "users.db";
    private static final int DATABASE_VERSION = 1;

    private static final String TABLE_USERS = "users";
    private static final String COLUMN_ID = "_id";
    private static final String COLUMN_NAME = "name";
    private static final String COLUMN_EMAIL = "email";
    private static final String COLUMN_PASSWORD = "password";

    private static final String CREATE_TABLE_USERS = "CREATE TABLE " +
            TABLE_USERS + "(" +
            COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
            COLUMN_NAME + " TEXT, " +
            COLUMN_EMAIL + " TEXT, " +
            COLUMN_PASSWORD + " TEXT" +
            ")";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE_USERS);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_USERS);
        onCreate(db);
    }

    public boolean registerUser(String name, String email, String password) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(COLUMN_NAME, name);
        values.put(COLUMN_EMAIL, email);
        values.put(COLUMN_PASSWORD, password);

        long result = db.insert(TABLE_USERS, null, values);
        return result != -1;
    }

    public boolean loginUser(String email, String password) {
        SQLiteDatabase db = this.getReadableDatabase();

        String selection = COLUMN_EMAIL + " = ? AND " + COLUMN_PASSWORD + " = ?";
        String[] selectionArgs = {email, password};

        Cursor cursor = db.query(
                TABLE_USERS,
                null,
                selection,
                selectionArgs,
                null,
                null,
                null
        );

        int count = cursor.getCount();

        cursor.close();

        return count > 0;
    }
}

在 LoginActivity 中，我们将使用 SQLite 数据库验证用户是否存在，并跳转到 MainActivity：

public class LoginActivity extends AppCompatActivity {
    private EditText mEmailEditText;
    private EditText mPasswordEditText;

    private DatabaseHelper mDatabaseHelper;

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

        mEmailEditText = findViewById(R.id.edit_email);
        mPasswordEditText = findViewById(R.id.edit_password);

        Button loginButton = findViewById(R.id.btn_login);
        loginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String email = mEmailEditText.getText().toString().trim();
                String password = mPasswordEditText.getText().toString().trim();

                if (email.isEmpty() || password.isEmpty()) {
                    Toast.makeText(LoginActivity.this, "Please enter email and password", Toast.LENGTH_SHORT).show();
                } else {
                    if (mDatabaseHelper.loginUser(email, password)) {
                        Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                        startActivity(intent);
                        finish();
                    } else {
                        Toast.makeText(LoginActivity.this, "Invalid email or password", Toast.LENGTH_SHORT).show();
                    }
                }
            }
        });

        TextView registerTextView = findViewById(R.id.txt_register);
        registerTextView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(LoginActivity.this, RegisterActivity.class);
                startActivity(intent);
            }
        });

        mDatabaseHelper = new DatabaseHelper(this);
    }
}

在 RegisterActivity 中，我们将使用 SQLite 数据库注册新用户：

public class RegisterActivity extends AppCompatActivity {
    private EditText mNameEditText;
    private EditText mEmailEditText;
    private EditText mPasswordEditText;

    private DatabaseHelper mDatabaseHelper;

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

        mNameEditText = findViewById(R.id.edit_name);
        mEmailEditText = findViewById(R.id.edit_email);
        mPasswordEditText = findViewById(R.id.edit_password);

        Button registerButton = findViewById(R.id.btn_register);
        registerButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = mNameEditText.getText().toString().trim();
                String email = mEmailEditText.getText().toString().trim();
                String password = mPasswordEditText.getText().toString().trim();

                if (name.isEmpty() || email.isEmpty() || password.isEmpty()) {
                    Toast.makeText(RegisterActivity.this, "Please enter name, email and password", Toast.LENGTH_SHORT).show();
                } else {
                    if (mDatabaseHelper.registerUser(name, email, password)) {
                        Toast.makeText(RegisterActivity.this, "Registration successful", Toast.LENGTH_SHORT).show();
                        finish();
                    } else {
                        Toast.makeText(RegisterActivity.this, "Registration failed", Toast.LENGTH_SHORT).show();
                    }
                }
            }
        });

        mDatabaseHelper = new DatabaseHelper(this);
    }
}

这样，我们就完成了一个简单的 Android 登录注册页面，使用 SQLite 数据库进行用户信息的保存和验证。