DBHelper.java

package edu.hebtu.movingcampus.db;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.provider.BaseColumns;

public class DBHelper extends SQLiteOpenHelper {

	private static final String DB_NAME = "movingcampus";
	private static final int DB_VERSION = 2;

	private SQLiteDatabase db;

	private static DBHelper mdbHelper;

	public static DBHelper getInstance(Context context) {
		if (mdbHelper == null) {
			mdbHelper = new DBHelper(context);
		}
		return mdbHelper;
	}

	private DBHelper(Context context) {
		super(context, DB_NAME, null, DB_VERSION);
	}

	private DBHelper(Context context, String name, CursorFactory factory,
			int version) {
		super(context, name, factory, version);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		this.db = db;
		operateTable(db, "");
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		if (oldVersion == newVersion) {
			return;
		}
		operateTable(db, "DROP TABLE IF EXISTS ");
		onCreate(db);
	}

	public void operateTable(SQLiteDatabase db, String actionString) {
		Class<DatabaseColumn>[] columnsClasses = DatabaseColumn.getSubClasses();
		DatabaseColumn columns = null;

		for (int i = 0; i < columnsClasses.length; i++) {
			try {
				columns = columnsClasses[i].newInstance();
				if ("".equals(actionString) || actionString == null) {
					db.execSQL(columns.getTableCreateor());
				} else {
					db.execSQL(actionString + columns.getTableName());
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

	}

	public long insert(String Table_Name, ContentValues values) {
		if (db == null)
			db = getWritableDatabase();
		return db.insert(Table_Name, null, values);
	}

	/**
	 * 
	 * @param Table_Name
	 * @param id
	 * @return 影响行数
	 */
	public int delete(String Table_Name, int id) {
		if (db == null)
			db = getWritableDatabase();
		return db.delete(Table_Name, BaseColumns._ID + "=?",
				new String[] { String.valueOf(id) });
	}

	/**
	 * @param Table_Name
	 * @param values
	 * @param WhereClause
	 * @param whereArgs
	 * @return 影响行数
	 */
	public int update(String Table_Name, ContentValues values,
			String WhereClause, String[] whereArgs) {
		if (db == null) {
			db = getWritableDatabase();
		}
		return db.update(Table_Name, values, WhereClause, whereArgs);
	}

	public Cursor query(String Table_Name, String[] columns, String whereStr,
			String[] whereArgs) {
		if (db == null) {
			db = getReadableDatabase();
		}
		return db.query(Table_Name, columns, whereStr, whereArgs, null, null,
				null);
	}

	public Cursor rawQuery(String sql, String[] args) {
		if (db == null) {
			db = getReadableDatabase();
		}
		Cursor c = db.rawQuery(sql, args);
		if (c.getCount() <= 0) {
			c.close();
			c = null;
		}
		return c;
	}

	public void ExecSQL(String sql) {
		if (db == null) {
			db = getWritableDatabase();
		}
		db.execSQL(sql);
	}

	public void closeDb() {
		if (db != null) {
			db.close();
			db = null;
		}
	}

}