Android foundation [Super detailed android storage method analysis (SharedPreferences, SQLite database storage)]

目录

1.Android存储方式

        1.1Android共有5medium storage：

2.SharedPreferences（文件存储）

        2.1简介

        2.2写入

        2.3读取

3.SQLite数据库存储

        3.1简介

        3.2创建

1.Android存储方式

        1.1Android共有5medium storage：

                SharedPreferences

                内部存储（Internal Storage）

                外部存储（External Storage）

                SQLite数据库存储

                网络存储（现阶段主流）

今天我们主要讲解SharedPreferences（文件存储）和SQLite数据库存储.

2.SharedPreferences（文件存储）

        2.1简介

                文件,相当于properties文件,数据存储都是使用键值对来存储.

        2.2写入

                a.获取SharedPreferences（①：getSharedPrefernces,②：getPrefernces)

                ①和②The difference between the acquisition method is the former two parameters（Store file name and mode of operation（int mode））,The latter has only one parameter of operation mode.

                b.借助Editor,向SharedPreferenxce中写入数据.

                c.写入数据,Only raw basic data can be written（boolean,float,int,long,String）,Compound data cannot be written.

                d.提交数据.

                调用 SharedPreferences.Editor 的 commit() method to submit updates to SharedPreferences 中.

        String name="zs";
        String pwd="123";

        SharedPreferences sp= getSharedPreferences("logininfo",MODE_PRIVATE);

        SharedPreferences.Editor edit = sp.edit();

        edit.putString("name",name);
        edit.putString("pwd",pwd);

        edit.commit();

        2.3读取

                a.获取sharedPrefernces.

                b.获取数据.

        SharedPreferences sp1= getSharedPreferences("logininfo",MODE_PRIVATE);

        String sp_name = sp1.getString("name", "");
        String sp_pwd = sp1.getString("pwd", "");

3.SQLite数据库存储

        3.1简介

                特点：轻量,无需配置.

                缺点：本地化.

        3.2创建

                a.用Class,DBHelper 继承SQLiteOpenHelper.

public class DBHelper extends SQLiteOpenHelper {

}

                b.实现两个抽象方法 onCreate() onUpgrade() 创建一个带参的构造方法.

public class DBHelper extends SQLiteOpenHelper {

    public DBHelper(@Nullable Context context) {

    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
}

                c.在构造方法中 创建数据库.

public class DBHelper extends SQLiteOpenHelper {

    public DBHelper(@Nullable Context context) {
        super(context, "school.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
}

                d.在onCreate() 方法中,创建表和插入数据.

public class DBHelper extends SQLiteOpenHelper {

    public DBHelper(@Nullable Context context) {
        super(context, "school.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {

        sqLiteDatabase.execSQL("create table student(sid integer primary key,sname text,sex text)");

        sqLiteDatabase.execSQL("insert into student values(1,'zs','男')");

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
}