记使用Android SQLite遇到的小问题

来源：互联网发布：2017七天网络成绩查询编辑：程序博客网时间：2024/05/01 10:55

引用请标明出处：http://blog.csdn.net/callon_h/article/details/51428341

之前一直是遇到activity需要保存数据就直接使用SQLite就好，但是有一天突然发现，我需要在其中一个Activity里访问另一个Activity建立的SQLiteDatabase，从而引出了该文。

查了很多资料，大多数都是说，使用单例模式建立继承SQLiteOpenHelper的类，然后使用静态方法（一般取名getInstance）来获得。自己亲自尝试了，发现总是不对，于是找了一种更简便更懒的方法（直接用文件位置引用数据库）：
SettingActivity.java

db = openOrCreateDatabase("callon_set_pump", Context.MODE_PRIVATE, null);        if(tabbleIsExist("table1")){            DatabaseHelper dbHelper = new DatabaseHelper(SettingActivity.this, "callon_set_pump");            SQLiteDatabase db = dbHelper.getReadableDatabase();            Cursor cursor = db.query("table1", new String[]{"id","name"}, "id=?", new String[]{"1"}, null, null, null);            while(cursor.moveToNext()){                String name = cursor.getString(cursor.getColumnIndex("name"));                //add your code here            }            cursor = db.query("table1", new String[]{"id","name"}, "id=?", new String[]{"2"}, null, null, null);            while(cursor.moveToNext()){                String name = cursor.getString(cursor.getColumnIndex("name"));                //add your code here            }            cursor = db.query("table1", new String[]{"id","name"}, "id=?", new String[]{"3"}, null, null, null);            while(cursor.moveToNext()){                String name = cursor.getString(cursor.getColumnIndex("name"));                //add your code here            }            cursor = db.query("table1", new String[]{"id","name"}, "id=?", new String[]{"4"}, null, null, null);            while(cursor.moveToNext()){                String name = cursor.getString(cursor.getColumnIndex("name"));                //add your code here            }            cursor = db.query("table1", new String[]{"id","name"}, "id=?", new String[]{"5"}, null, null, null);            while(cursor.moveToNext()){                String name = cursor.getString(cursor.getColumnIndex("name"));               //add your code here            }        }        else {            db.execSQL("CREATE TABLE table1(id int,name varchar(20))");            ContentValues values = new ContentValues();            values.put("id", 1);            values.put("name", "5000");            db.insert("table1", null, values);            values = new ContentValues();            values.put("id", 2);            values.put("name", "1000");            db.insert("table1", null, values);            values = new ContentValues();            values.put("id", 3);            values.put("name", "3");            db.insert("table1", null, values);            values = new ContentValues();            values.put("id", 4);            values.put("name", "3");            db.insert("table1", null, values);            values = new ContentValues();            values.put("id", 5);            values.put("name", "NONE");            db.insert("table1", null, values);            //add your code here        }

上述类建立了一个数据库callon_set_pump，在另一个类中使用的话，
PageActivity.java

db_set = SQLiteDatabase.openOrCreateDatabase("data/data/com.autopump.callon.nenu/databases/callon_set_pump",null);        Cursor cursor = db_set.query("table1", new String[]{"id","name"}, "id=?", new String[]{"1"}, null, null, null);        while(cursor.moveToNext()){            String name = cursor.getString(cursor.getColumnIndex("name"));            System.out.println("name is :"+ name);        }

关于tabbleIsExist方法，它是用来检测是否存在该数据库的，如果存在重复创建会出现异常的哦～

private boolean tabbleIsExist(String tableName){        boolean result = false;        if(tableName == null){            return false;        }        SQLiteDatabase db = null;        DatabaseHelper dbHelper = new DatabaseHelper(SettingActivity.this, "callon_set_pump");        Cursor cursor = null;        try {            db = dbHelper.getReadableDatabase();            String sql = "select count(*) as c from Sqlite_master  where type ='table' and name ='"+tableName.trim()+"' ";            cursor = db.rawQuery(sql, null);            if(cursor.moveToNext()){                int count = cursor.getInt(0);                if(count>0){                    result = true;                }            }        } catch (Exception e) {            // TODO: handle exception        }        return result;    }

总之能抓到耗子的就是好猫吧，虽然方法不像什么单例模式那样洋气，希望对大家有帮助。

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