leader讓我給他寫一個簡單的數據庫類demo

之前也沒有寫過相關的文檔，為了以后使用方便，總結一下：

public class DataBaseHelper extends SQLiteOpenHelper {	PRivate static final String DATABASE_NAME = "demo.db";// 數據庫名	private static final int DATABASE_VERSION = 1;// 數據版本號	private SQLiteDatabase mSqLiteDatabase;	private static final String TABLE_NAME = "table_name";// 表名	public static final String ID = "id";	public static final String NAME = "name";	public static final String AGE = "age";	public static final String GENDER = "gender";	public DataBaseHelper(Context context) {		super(context, DATABASE_NAME, null, DATABASE_VERSION);		mSqLiteDatabase = getWritableDatabase();	}	@Override	public SQLiteDatabase getWritableDatabase() {		// TODO Auto-generated method stub		if (mSqLiteDatabase == null) {			mSqLiteDatabase = super.getWritableDatabase();		}		return mSqLiteDatabase;	}	@Override	public void onCreate(SQLiteDatabase db) {		// TODO Auto-generated method stub		mSqLiteDatabase = db;		initDB();	}	  /**     * 創建數據庫表     */    private void initDB() {        mSqLiteDatabase.execSQL("CREATE TABLE " + TABLE_NAME + "(" +                ID + " INTEGER PRIMARY KEY," +                NAME + " VARCHAR," +                AGE + " INTEGER," +                GENDER + " VARCHAR" +                ");");    }	/**	 * 插入數據庫	 * 	 * @param list	 */	public void insert(List<PeopleInfo> list) {		if (list == null || list.size() < 1) {			return;		}		int length = list.size();		for (int i = 0; i < length; i++) {			insert(list.get(i));		}	}	/**	 * 插入數據庫	 * 	 * @param peopleInfo	 */	private void insert(PeopleInfo peopleInfo) {		// TODO Auto-generated method stub		ContentValues values = new ContentValues();		values.put(ID, peopleInfo.getID());		values.put(NAME, peopleInfo.getName());		values.put(AGE, peopleInfo.getAge());		values.put(GENDER, peopleInfo.getGender());		mSqLiteDatabase.insert(TABLE_NAME, null, values);	}	/**	 * 刪除數據庫表	 */	public void dropTable() {		String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;		mSqLiteDatabase.execSQL(sql);	}	/**	 * 刪除表中對應列	 * 	 * @param name	 */	public void deleteItem(int id) {		String sql = "DELETE FROM " + TABLE_NAME + " WHERE " + ID + "=" + id;		mSqLiteDatabase.execSQL(sql);	}	/**	 * 刪除表數據不刪除表	 */	public void deleteTable() {		String sql = "DELETE FROM " + TABLE_NAME;		mSqLiteDatabase.execSQL(sql);	}	/**	 * 更新數據庫表數據	 * 	 * @param peopleInfo	 */	public void update(PeopleInfo peopleInfo) {		ContentValues values = new ContentValues();		values.put(NAME, peopleInfo.getName());		values.put(AGE, peopleInfo.getAge());		values.put(GENDER, peopleInfo.getGender());		mSqLiteDatabase.update(TABLE_NAME, values, "id=?",				new String[] { String.valueOf(peopleInfo.getID()) });	}	private Cursor getAll() {		String sql = "SELECT * FROM " + TABLE_NAME;		return mSqLiteDatabase.rawQuery(sql, null);	}	/**	 * 獲取表中所有數據	 * 	 * @return	 */	public List<PeopleInfo> getDBAllData() {		List<PeopleInfo> list = new ArrayList<PeopleInfo>();		Cursor mCursor = getAll();		int idIndex = mCursor.getColumnIndexOrThrow(ID);		int nameIndex = mCursor.getColumnIndexOrThrow(NAME);		int ageIndex = mCursor.getColumnIndexOrThrow(AGE);		int genderIndex = mCursor.getColumnIndexOrThrow(GENDER);		while (mCursor.moveToNext()) {			PeopleInfo info = new PeopleInfo();			info.setID(mCursor.getInt(idIndex));			info.setName(mCursor.getString(nameIndex));			info.setAge(mCursor.getInt(ageIndex));			info.setGender(mCursor.getString(genderIndex));			list.add(info);		}		mCursor.close();		return list;	}	@Override	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {		// TODO Auto-generated method stub		mSqLiteDatabase = db;		if (oldVersion != newVersion) {			dropTable();		}		onCreate(db);	}}