Android数据存储的五种方式2

FileInputStream fis;
BufferedReader br;
File file = new File(getCacheDir(), "gjcData");
try {
  fis = new FileInputStream(file);
  br = new BufferedReader(new InputStreamReader(fis));
  String line = br.readLine();
  while(line!=null){
    line = br.readLine();
  }
} catch (Exception e) {
  e.printStackTrace();
} finally {
  br.close();
  fis.close();
}

<!-- 允许程序写入外部存储-->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

FileOutputStream fos;
BufferedWriter bw;
// 创建gjcData文件对象，由于不同手机SDcard目录不同，所以我们通过Environment.getExternalStorageDirectory()获取路径
File file = new File(Environment.getExternalStorageDirectory(), "gjcData");
if (!file.exists()){
  try {
    file.createNewFile();
  } catch (Exception e) {
    e.printStackTrace();
  }
}
try {
  fos =new FileOutputStream(file);
  bw = new BufferedWriter(new OutputStreamWriter(fos));
  bw.write("Hello world");
  bw.flush();
} catch (Exception e) {
  e.printStackTrace();
} finally {
  bw.close();
  fos.close();
}

FileInputStream fis;
BufferedReader br;
File file = new File(Environment.getExternalStorageDirectory(), "gjcData");
try {
  fis = new FileInputStream(file);
  br =  new BufferedReader(new InputStreamReader(fis));
  String line = br.readLine();
  while(line!=null){
    line = br.readLine();
  }
} catch (Exception e) {
  e.printStackTrace();
} finally {
  br.close();
  fis.close();
}

public class MySQLiteOpenHelper extends SQLiteOpenHelper {

     // 构造器,传入四个参数（Context上下文环境，String数据库名字，CursorFactory操作数据库的Cursor对象(通常为null)，int数据库版本号） 
    public MySQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }
    
    // 自定义的构造器
    public MySQLiteOpenHelper(Context context, String name) {
        this(context, name, null, 1);//传入Context和数据库的名称，调用上面的构造器
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        // 在创建数据库时，创建一个user数据表
        String sql = "create table if not exists user(id integer primary key  autoincrement, name varchar(20), password varchar(20))";
        sqLiteDatabase.execSQL(sql);
    }
    
    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
      //用于修改数据库版本（第一个参数是SQLiteDatabase对象，第二个参数是旧的版本号，第三个参数是新版本号。一般我们在这个方法里边删除数据库表，并建立新的数据库表）
    }
}