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/<packagename>/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/<packagename>/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/<packagename>/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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