Android 一個應用多個數據庫
阿新 • • 發佈:2018-12-17
最近在做一個 IM 的專案,需要儲存大量資料到本地資料庫。考慮到同一臺手機可能會被多個賬號登入使用,為了提升資料庫查詢的效率,以分庫的方式來儲存不同賬號的資料(使用使用者賬號來作為資料庫名稱)。
以儲存使用者資訊為例:
- 先貼出使用程式碼:
mUserDAO = new UserDAO(this, account); // 此處的 account 就是要操作的資料庫名稱
mUserDAO.insert(new User(account, userName));
- 以下為三個關鍵類
/** * 資料庫幫助類 * * @author zch * @since 2018-01-05 */ public class DBHelper extends SQLiteOpenHelper { private static final int DB_VERSION = 1; public static final String TABLE_NAME = "user"; public DBHelper(Context context, String dbName) { super(context, dbName, null, DB_VERSION); } @Override public void onCreate(SQLiteDatabase db) { String sql = "create table if not exists " + TABLE_NAME + " (account text primary key , userName text)"; db.execSQL(sql); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { String sql = "drop table if exists " + TABLE_NAME; db.execSQL(sql); onCreate(db); } }
/**
* 使用者實體類
*
* @author zch
* @since 2018-01-05
*/
public class User {
public String account; // 使用者賬號,假設唯一,用它作為資料庫名稱(dbName)
public String userName;
public User(String account, String userName) {
this.account = account;
this.userName = userName;
}
}
/** * 使用者資料表相關操作 * * @author zch * @since 2018-01-05 */ public class UserDAO { private DBHelper mDBHelper; public UserDAO(Context context, String dbName) { mDBHelper = new DBHelper(context, dbName); } /** * 插入一條資料 * * @param user * @return */ public boolean insert(User user) { SQLiteDatabase db = null; try { db = mDBHelper.getWritableDatabase(); db.beginTransaction(); ContentValues values = new ContentValues(); values.put("account", user.account); values.put("userName", user.userName); db.insertOrThrow(DBHelper.TABLE_NAME, null, values); db.setTransactionSuccessful(); return true; } catch (SQLException e) { e.printStackTrace(); } finally { if (null != db) { try { db.endTransaction(); db.close(); } catch (Exception e) { e.printStackTrace(); } } } return false; } /** * 刪除一條資料 * * @param user * @return */ public boolean delete(User user) { SQLiteDatabase db = null; try { db = mDBHelper.getWritableDatabase(); db.beginTransaction(); db.delete(DBHelper.TABLE_NAME, "account = ?", new String[]{user.account}); db.setTransactionSuccessful(); return true; } catch (Exception e) { e.printStackTrace(); } finally { if (null != db) { try { db.endTransaction(); db.close(); } catch (Exception e) { e.printStackTrace(); } } } return false; } /** * 獲取所有資料 * * @return */ public List<User> getUserList() { SQLiteDatabase db = null; Cursor cursor = null; try { db = mDBHelper.getReadableDatabase(); cursor = db.query(DBHelper.TABLE_NAME, new String[]{"account", "userName"}, null, null, null, null, null); if (cursor.getCount() > 0) { List<User> userList = new ArrayList<>(); while (cursor.moveToNext()) { User user = new User(cursor.getString(cursor.getColumnIndex("account")), cursor.getString(cursor.getColumnIndex("userName"))); userList.add(user); } return userList; } } catch (Exception e) { e.printStackTrace(); } finally { if (null != cursor) { try { cursor.close(); } catch (Exception e) { e.printStackTrace(); } } if (null != db) { try { db.close(); } catch (Exception e) { e.printStackTrace(); } } } return null; } }