Android SQLite数据库连接实现登录功能

Android SQLite数据库连接实现登录功能攻略

1. 创建数据库和表格

首先，我们需要创建一个SQLite数据库和一个用于存储用户信息的表格。可以在SQLiteOpenHelper类中实现这一步骤。

public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = \"UserDB\";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_NAME = \"User\";
    private static final String COLUMN_ID = \"id\";
    private static final String COLUMN_USERNAME = \"username\";
    private static final String COLUMN_PASSWORD = \"password\";

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTableQuery = \"CREATE TABLE \" + TABLE_NAME + \"(\"
                + COLUMN_ID + \" INTEGER PRIMARY KEY AUTOINCREMENT, \"
                + COLUMN_USERNAME + \" TEXT, \"
                + COLUMN_PASSWORD + \" TEXT)\";
        db.execSQL(createTableQuery);
    }

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

2. 注册用户

在注册用户时，我们需要将用户提供的用户名和密码插入到数据库表格中。

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public class MainActivity extends AppCompatActivity {
    private EditText usernameEditText;
    private EditText passwordEditText;
    private Button registerButton;

    private DatabaseHelper databaseHelper;

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

        usernameEditText = findViewById(R.id.usernameEditText);
        passwordEditText = findViewById(R.id.passwordEditText);
        registerButton = findViewById(R.id.registerButton);

        databaseHelper = new DatabaseHelper(this);

        registerButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String username = usernameEditText.getText().toString();
                String password = passwordEditText.getText().toString();

                SQLiteDatabase db = databaseHelper.getWritableDatabase();
                ContentValues values = new ContentValues();
                values.put(DatabaseHelper.COLUMN_USERNAME, username);
                values.put(DatabaseHelper.COLUMN_PASSWORD, password);
                db.insert(DatabaseHelper.TABLE_NAME, null, values);

                Toast.makeText(MainActivity.this, \"User registered successfully\", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

3. 用户登录

在用户登录时，我们需要查询数据库表格，检查提供的用户名和密码是否匹配。

public class LoginActivity extends AppCompatActivity {
    private EditText usernameEditText;
    private EditText passwordEditText;
    private Button loginButton;

    private DatabaseHelper databaseHelper;

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

        usernameEditText = findViewById(R.id.usernameEditText);
        passwordEditText = findViewById(R.id.passwordEditText);
        loginButton = findViewById(R.id.loginButton);

        databaseHelper = new DatabaseHelper(this);

        loginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String username = usernameEditText.getText().toString();
                String password = passwordEditText.getText().toString();

                SQLiteDatabase db = databaseHelper.getReadableDatabase();
                String[] projection = {DatabaseHelper.COLUMN_USERNAME, DatabaseHelper.COLUMN_PASSWORD};
                String selection = DatabaseHelper.COLUMN_USERNAME + \" = ? AND \" + DatabaseHelper.COLUMN_PASSWORD + \" = ?\";
                String[] selectionArgs = {username, password};
                Cursor cursor = db.query(DatabaseHelper.TABLE_NAME, projection, selection, selectionArgs, null, null, null);

                if (cursor.moveToFirst()) {
                    Toast.makeText(LoginActivity.this, \"Login successful\", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(LoginActivity.this, \"Invalid username or password\", Toast.LENGTH_SHORT).show();
                }

                cursor.close();
            }
        });
    }
}

以上是实现Android SQLite数据库连接并实现登录功能的完整攻略。在注册用户和用户登录的示例中，我们使用了DatabaseHelper类来创建数据库和表格，并使用SQLiteDatabase类执行数据库操作。

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