如何从 sqlite Android 获取 id

Question

我在获取用户 ID 时遇到了问题。我可以获取姓名、电子邮件、created_at 列，但无法获取 ID。请帮忙

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

// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
    String CREATE_LOGIN_TABLE = "CREATE TABLE " + TABLE_USER + "("
            + KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT,"
            + KEY_EMAIL +  " TEXT,"
            + KEY_CREATED_AT + " TEXT" + ")";
    db.execSQL(CREATE_LOGIN_TABLE);

    Log.d(TAG, "Database tables created");
}

// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_USER);

    // Create tables again
    onCreate(db);
}

/**
 * Storing user details in database
 * */
public void addUser(String name, String email,  String created_at) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put(KEY_NAME, name); // Name
    values.put(KEY_EMAIL, email); // Email
    values.put(KEY_CREATED_AT, created_at); // Created At

    // Inserting Row
    long id = db.insert(TABLE_USER, null, values);
    db.close(); // Closing database connection

    Log.d(TAG, "New user inserted into sqlite: " + id);
}

/**
 * Getting user data from database
 * */
public HashMap<String, String> getUserDetails() {
    HashMap<String, String> user = new HashMap<String, String>();
    String selectQuery = "SELECT * FROM " + TABLE_USER;

    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);
    // Move to first row
    cursor.moveToFirst();
    if (cursor.getCount() > 0) {
        user.put("name", cursor.getString(1));
        user.put("email", cursor.getString(2));
        user.put("created_at", cursor.getString(3));
    }
    cursor.close();
    db.close();
    // return user
    Log.d(TAG, "Fetching user from Sqlite: " + user.toString());

    return user;
}

/**
 * Re crate database Delete all tables and create them again
 * */
public void deleteUsers() {
    SQLiteDatabase db = this.getWritableDatabase();
    // Delete All Rows
    db.delete(TABLE_USER, null, null);
    db.close();

    Log.d(TAG, "Deleted all user info from sqlite");
}`

获取结果：

D/SQLiteHandler: Fetching user from Sqlite: {name=admin, created_at=2020-05-06 22:04:39, email=admin@gmail.com}

Answer 1

Cursor 对象的列索引是基于 0 的，因此列 KEY_ID 的索引是 0 并且您没有将它添加到 HashMap.
更改为：

if (cursor.getCount() > 0) {
    user.put(KEY_ID, cursor.getString(0));
    user.put(KEY_NAME, cursor.getString(1));
    user.put(KEY_EMAIL, cursor.getString(2));
    user.put(KEY_CREATED_AT, cursor.getString(3));
}

最好在整个代码中使用 KEY_??? 常量。
也代替列索引 0,1,2... 使用方法 getColumnIndex():

if (cursor.getCount() > 0) {
    user.put(KEY_ID, cursor.getString(getColumnIndex(KEY_ID)));
    user.put(KEY_NAME, cursor.getString(getColumnIndex(KEY_NAME)));
    user.put(KEY_EMAIL, cursor.getString(getColumnIndex(KEY_EMAIL)));
    user.put(KEY_CREATED_AT, cursor.getString(getColumnIndex(KEY_CREATED_AT)));
}

如何从 sqlite Android 获取 id

How to get id from sqlite Android

sqlite

android

android-sqlite