Android SQLite Database Data Retrieval Guide

1 year ago
Olivia Parker
2 minutes

To obtain Android database data, you can follow the steps below:

  1. Create a SQLite database and the corresponding tables. The SQLiteOpenHelper class can be used to assist in creating and managing the database.
  2. In your database class, create a method to retrieve data. This method should return a Cursor object containing the query results.
  3. In your activity or fragment, retrieve a Cursor object by calling the query method. You can use the ContentResolver class to obtain the Cursor.
  4. Use the Cursor object to iterate over the query results and extract the necessary data.

Here is a simple example code for retrieving data from a database:

// Step 1: 创建数据库类
public class MyDatabaseHelper extends SQLiteOpenHelper {
    // 构造方法
    public MyDatabaseHelper(Context context) {
        super(context, "mydatabase.db", null, 1);
    }

    // 创建表格
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE mytable (id INTEGER PRIMARY KEY, name TEXT)");
    }

    // 升级数据库
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // 升级逻辑
    }

    // Step 2: 创建查询方法
    public Cursor getData() {
        SQLiteDatabase db = this.getReadableDatabase();
        return db.query("mytable", null, null, null, null, null, null);
    }
}

// Step 3: 在活动或碎片中获取数据库数据
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 获取数据库数据
        MyDatabaseHelper dbHelper = new MyDatabaseHelper(this);
        Cursor cursor = dbHelper.getData();

        // 遍历查询结果
        if (cursor != null && cursor.moveToFirst()) {
            do {
                int id = cursor.getInt(cursor.getColumnIndex("id"));
                String name = cursor.getString(cursor.getColumnIndex("name"));
                // 对数据进行处理
            } while (cursor.moveToNext());
        }

        // 关闭Cursor和数据库连接
        if (cursor != null) {
            cursor.close();
        }
        dbHelper.close();
    }
}

Please note that this is just a simple example and real situations may be more complex. You may need to use parameters and filters to query data more accurately, and use appropriate methods to process and display the query results.

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