android检查sqlite数据库中是否存在某个元素

private boolean search_city(String str) {

CityDBHelper dbHelper = new CityDBHelper(MainActivity.this,
"city_db_2", null, 1);
SQLiteDatabase db = dbHelper.getWritableDatabase();

Cursor cursor = db.rawQuery(
"select * from   city_table  where   city=? ",
new String[] { str });
while (cursor.moveToNext()) {
db.close();
Log.i(" search_city_name_exist", str + "在数据库已存在,return true");
return true;// //有城市在数据库已存在，返回true
}
db.close();
Log.i(" search_city_name_exist", str + "在数据库不存在，return false");
return false;// //在数据库以前存在 false

}

经测试，是正确可靠的

<img src="https://img-blog.csdn.net/20151203000731879" alt="" />