Android持久化存储总结

本文旨在复习总结Android持久化存储方法，只列出了主要代码以及少量批注，仅作为复习参考使用。

文件存储

所有文件默认放在/data/data//files/目录下

文件写入

    public void save(String inputText){        FileOutputStream out=null;        BufferedWriter writer=null;        try {            out=openFileOutput("data", Context.MODE_PRIVATE);            writer=new BufferedWriter(new OutputStreamWriter(out));            writer.write(inputText);        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }finally {            if(writer!=null){                try {                    writer.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }

读取文件

    public String load(){        FileInputStream in =null;        BufferedReader reader=null;        StringBuilder content=new StringBuilder();        try {            in=openFileInput("data");            reader=new BufferedReader(new InputStreamReader(in));            String line="";            while ((line=reader.readLine())!=null){                content.append(line);            }        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }finally {            if(reader!=null){                try {                    reader.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }        return content.toString();    }

SharePreferences方法

SharePreference文件默认放在/data/data//shared_prefs/目录下

SharedPreferences写入

SharedPreferences.Editor editor=getSharedPreferences("data",MODE_PRIVATE).edit();editor.putString("et_inputText","sharePreferences test");editor.commit();

SharedPreferences读取

SharedPreferences sp=getSharedPreferences("data",MODE_PRIVATE);String input=sp.getString("et_inputText","请输入用户名");//第二个参数是为空的默认信息

SQLite数据库存储

SQLite文件默认放在/data/data//databases/目录下

public class MyDataBaseHelper extends SQLiteOpenHelper{    private static final String CREATE_BOOK="create table Book("            +"id integer primary key autoincrement, "            +"author text, "            +"price real, "            +"pages integer, "            +"name text)";    private static final String CREATE_CATEGORY="create table Category("            +"id integer primary key autoincrement, "            +"category_name text, "            +"category_code integer)";    private Context mContext;    public MyDataBaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);        mContext=context;    }    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL(CREATE_BOOK);        db.execSQL(CREATE_CATEGORY);        Toast.makeText(mContext,"create succeed",Toast.LENGTH_SHORT).show();    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        db.execSQL("drop table if exists Book");        db.execSQL("drop table if exists Category");        onCreate(db);    }

创建数据库

 dbHelper=new MyDataBaseHelper(this,"BookStore.db",null,2);

插入数据

SQLiteDatabase db=dbHelper.getWritableDatabase();ContentValues values=new ContentValues();values.put("name","Effective Java");values.put("author","Joshua Bloch");values.put("pages",454);values.put("price",16.96);db.insert("Book",null,values);

更新数据

ContentValues values=new ContentValues();values.put("price",198.00);SQLiteDatabase db=dbHelper.getReadableDatabase();db.update("Book",values,"name=?",new String[]{"Android Programme"});

删除行

SQLiteDatabase db = dbHelper.getWritableDatabase();db.delete("Book", "pages > ?", new String[] { "500" });

ContentValues知识android提供的一个便于数据库操作的类，为数据库操作提供便利，也可以直接使用数据库语句进行操作

参考书目《第一行代码》

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