package com.asc.db;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;/** * 数据库公共类，提供基本数据库操作*/public class DBManager {    // 默认数据库    private static final String DB_NAME = "asc.db";    // 数据库版本    private static final int DB_VERSION = 1;    // 执行open()打开数据库时，保存返回的数据库对象    private SQLiteDatabase mSQLiteDatabase = null;    // 由SQLiteOpenHelper继承过来    private DatabaseHelper mDatabaseHelper = null;    // 本地Context对象    private Context mContext = null;        private static DBManager dbConn= null;        // 查询游标对象    private Cursor cursor;    /**     * SQLiteOpenHelper内部类     */    private static class DatabaseHelper extends SQLiteOpenHelper {        DatabaseHelper(Context context) {            // 当调用getWritableDatabase()或 getReadableDatabase()方法时,创建一个数据库            super(context, DB_NAME, null, DB_VERSION);        }        @Override        public void onCreate(SQLiteDatabase db) {            db.execSQL("CREATE TABLE ad_record(id PRIMARY KEY NOT NULL, adUrl TEXT, apMac TEXT, createDate DATETIME);");        }        @Override        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {            db.execSQL("DROP TABLE IF EXISTS ad_record");            onCreate(db);        }    }    /**     * 构造函数     *      * @param mContext     */    private DBManager(Context mContext) {        super();        this.mContext = mContext;    }        public static DBManager getInstance(Context mContext){        if (null == dbConn) {            dbConn = new DBManager(mContext);        }        return dbConn;    }    /**     * 打开数据库     */    public void open() {        mDatabaseHelper = new DatabaseHelper(mContext);        mSQLiteDatabase = mDatabaseHelper.getWritableDatabase();    }    /**     * 关闭数据库     */    public void close() {        if (null != mDatabaseHelper) {            mDatabaseHelper.close();        }        if (null != cursor) {            cursor.close();        }    }    /**     * 插入数据     * @param tableName 表名     * @param nullColumn null     * @param contentValues 名值对     * @return 新插入数据的ID，错误返回-1     * @throws Exception     */    public long insert(String tableName, String nullColumn,            ContentValues contentValues) throws Exception {        try {            return mSQLiteDatabase.insert(tableName, nullColumn, contentValues);        } catch (Exception e) {            throw e;        }    }    /**     * 通过主键ID删除数据     * @param tableName 表名     * @param key 主键名     * @param id 主键值     * @return 受影响的记录数     * @throws Exception     */    public long delete(String tableName, String key, int id) throws Exception {        try {            return mSQLiteDatabase.delete(tableName, key + " = " + id, null);        } catch (Exception e) {            throw e;        }    }        /**     * 查找表的所有数据     * @param tableName 表名     * @param columns 如果返回所有列，则填null     * @return     * @throws Exception     */    public Cursor findAll(String tableName, String [] columns) throws Exception{        try {            cursor = mSQLiteDatabase.query(tableName, columns, null, null, null, null, null);            cursor.moveToFirst();            return cursor;        } catch (Exception e) {            throw e;        }    }        /**     * 根据主键查找数据     * @param tableName 表名     * @param key 主键名     * @param id  主键值     * @param columns 如果返回所有列，则填null     * @return Cursor游标     * @throws Exception      */    public Cursor findById(String tableName, String key, int id, String [] columns) throws Exception {        try {            return mSQLiteDatabase.query(tableName, columns, key + " = " + id, null, null, null, null);        } catch (Exception e) {            throw e;        }    }        /**     * 根据条件查询数据     * @param tableName 表名     * @param names 查询条件     * @param values 查询条件值     * @param columns 如果返回所有列，则填null     * @param orderColumn 排序的列     * @param limit 限制返回数     * @return Cursor游标     * @throws Exception     */    public Cursor find(String tableName, String [] names, String [] values, String [] columns, String orderColumn, String limit) throws Exception{        try {            StringBuffer selection = new StringBuffer();            for (int i = 0; i < names.length; i++) {                selection.append(names[i]);                selection.append(" = ?");                if (i != names.length - 1) {                    selection.append(",");                }            }            cursor = mSQLiteDatabase.query(true, tableName, columns, selection.toString(), values, null, null, orderColumn, limit);            cursor.moveToFirst();            return cursor;        } catch (Exception e) {            throw e;        }    }        /**     *      * @param tableName 表名     * @param names 查询条件     * @param values 查询条件值     * @param args 更新列-值对     * @return true或false     * @throws Exception     */    public boolean udpate(String tableName, String [] names, String [] values, ContentValues args) throws Exception{        try {            StringBuffer selection = new StringBuffer();            for (int i = 0; i < names.length; i++) {                selection.append(names[i]);                selection.append(" = ?");                if (i != names.length - 1) {                    selection.append(",");                }            }            return mSQLiteDatabase.update(tableName, args, selection.toString(), values) > 0;        } catch (Exception e) {            throw e;        }    }        /**     * 执行sql语句，包括创建表、删除、插入     *      * @param sql     */    public void executeSql(String sql) {        mSQLiteDatabase.execSQL(sql);    }}