用android写一个数据库帮助类
时间: 2023-05-31 14:03:54 浏览: 57
以下是一个简单的Android数据库帮助类的示例:
```
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "mydatabase.db";
private static final int DATABASE_VERSION = 1;
// Table name and column names
public static final String TABLE_NAME = "mytable";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_NAME = "name";
public static final String COLUMN_AGE = "age";
// SQL statement to create the table
private static final String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + " (" +
COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
COLUMN_NAME + " TEXT, " +
COLUMN_AGE + " INTEGER);";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// Create the table
db.execSQL(CREATE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Upgrade the database
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
}
```
这个帮助类创建了一个名为“mydatabase.db”的数据库,并在其中创建了一个名为“mytable”的表,该表包含三个列:_id,name和age。
要在应用程序中使用这个帮助类,可以创建一个新的DatabaseHelper实例并获取一个可写的SQLiteDatabase对象,如下所示:
```
DatabaseHelper helper = new DatabaseHelper(context);
SQLiteDatabase db = helper.getWritableDatabase();
```
现在您可以使用SQLiteDatabase对象执行SQL查询和更新。例如,以下代码将插入一行数据到“mytable”表中:
```
ContentValues values = new ContentValues();
values.put(DatabaseHelper.COLUMN_NAME, "John");
values.put(DatabaseHelper.COLUMN_AGE, 30);
db.insert(DatabaseHelper.TABLE_NAME, null, values);
```