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遍历Symbian某目录下的所有文件
http://www.21tx.com 2009年11月25日 天极网

  遍历Symbian某目录下的所有文件应该是Symbian中常用到的功能模块,比如你想写一个类似“程序管理器”的程序,那么首先的任务就是要先知道某目录下到底有那些文件,然后再筛选出你所需要的文件。

  遍历Symbian某目录下的所有文件有两种方法

  ① 我们首先学习点预备知识

  查看SDK HELP中的GetDir()方法,你会看到如下的内容:

  GetDir()

  TInt GetDir(const TDesC& aName,TUint anEntryAttMask,TUint anEntrySortKey, CDir*& anEntryList) const;

  Description

  Gets a filtered list of a directory's contents. The bitmask determines which file and directory entry types should be listed. The sort key determines the order in which they are listed.

  注释:

  得到一个目录下内容的过滤列表。

  anEntryAttMask决定哪个文件和目录应该被列出。

  anEntrySortKey决定这些内容按照什么顺序列出。

  Notes:

  If sorting by UID (ESortByUid is OR'ed with the entry sort key), then UID information will be included in the listing whether or not KEntryAttAllowUid is specified in anEntryAttMask.(如果按照UID排序,即anEntrySortKey参数的值定义为ESortByUid。那么UID信息将被包含在列表中不管anEntryAttMask参数是否定义了KEntryAttAllowUid)

  The function sets anEntryList to NULL, then allocates memory for it before appending entries to the list. Therefore, anEntryList should have no memory allocated to it before this function is called, otherwise this memory will become orphaned.(这个函数把anEntryList参数设置为NULL,然后在添加文件项到列表之前为anEntryList分配内存空间。因此,该函数调用之前anEntryList应该没有分配内存,否则这部分内存会变成垃圾而被遗弃)

  The caller of this function is responsible for deleting anEntryList after the function has returned.(此函数的调用者有责任删除anEntryList在函数返回)

  Parameters

  const TDesC& aNameName of the directory for which a listing is required. Wildcards may be used to specify particular files.

  TUint anEntryAttMaskBitmask indicating the attributes of interest. Only files and directories whose attributes match those specified here can be included in the listing. For more information see KEntryAttMatchMask and the other directory entry details. Also see KEntryAttNormal and the other file or directory attributes.

  TUint anEntrySortKeyFlag indicating the order in which the entries are to be sorted. This flag is defined in TEntryKey.

  CDir*& anEntryListOn return contains a list of directory and file entries.

  Return value

  TIntKErrNone if successful, otherwise another of the system-wide error codes.

  这是RFs类中的一个方法,从上面的SDK HELP内容我们可以看出:如果我们想获取某个目录下的所有内容,那么只需获取相应目录的CDir指针即可。

  那么我们再看看CDir这个类的SDK HELP:

  Class CDir

  CDir

  Support

  Supported from 5.0

  Description

  Array of directory entries that has been read into memory from the file system — abstract base class. It can be read and sorted by user programs, but cannot be created by them.

  This class is not intended for user derivation.

  注释:一个数组,这个数组的内容是从文件系统扫描到的目录,目录被缓存到内存中。它可以被我们的程序读取和排序,但是不能创建。

  Derivation

  o CBase - Base class for all classes to be instantiated on the heap

  § CDir - Array of directory entries that has been read into memory from the file system — abstract base class

  Members

  Defined in CDir:

  Count(), NewL(), Sort(), operator[](), ~CDir()

  Inherited from CBase:

  operator new()

  可见,这个类派生自CBase,并且继承了CBase的new()运算符。它里面只有5个方法,去处析构函数,实际上只有4个有用的方法。并且它里面重新定义了[]操作符,因为CDir本身是一个目录的数组。它还可以排序、可以计算数量,这些都是数组的基本特性。NewL()只不过也是一个重载的运算符而已。

  再看看operator[]()的定义:

  operator[]()

  const TEntry& operator[](TInt anIndex) const;

  Description

  Returns an entry from the array.

  Parameters

  TInt anIndexIndex of the desired entry within the array.

  Return value

  TEntry&A directory entry.

  可以看出,通过[]操作符,CDir指针返回给我们的是一个目录的封装类TEntry。

  我们可以再跟踪一下TEntry这个类的SDK HELP:

  Class TEntry

  TEntry

  Support

  Supported from 5.0

  Description

  Encapsulates an entry in a directory, which can be another (nested) directory, a file or a volume label. Each directory entry has a name which is relative to its owning directory and a type, which is indicated by its unique identifier (UID).

  注释:封装目录中的一项内容,内容可以是另一个(嵌套的)目录、一个文件或者是一个驱动器卷标。每个目录项都有一个名字和类型与它的所属目录相关联,也就是UID所显示出来的东西。

  An entry can be interrogated for the following properties:

  一项内容可以被提取以下的属性:

  · the kind of entry: stored in the entry UIDs, stored in iType(项的类型:储存在UIDs和iType中)

  · the entry attributes, stored in iAtt(项的属性:储存在iAtt中)

  · the size of entry(项的尺寸)

  · the time the entry was last modified(项上次被修改的时间)

  Members

  Defined in TEntry:

  IsArchive(), IsDir(), IsHidden(), IsReadOnly(), IsSystem(), IsTypeValid(), IsUidPresent(), MostDerivedUid(), iAtt, iModified, iName, iSize, iType, operator[]()

  See also:

  File or directory attributes

  通过以上SDK HELP的内容,我们就知道了大概的方向,从而尝试写出了以下的程序:

  void CCountEntryAppUi::ConstructL()

  {

  BaseConstructL();

  RFs iFs;

  User::LeaveIfError(iFs.Connect());

  _LIT(KDIR,"C:\\");

  CDir* dir;

  User::LeaveIfError(iFs.GetDir(KDIR,KEntryAttNormal|KEntryAttMatchMask,ESortByDate,dir));

  TInt tempInt = dir->Count();

  for(int i = 0;i < tempInt;i++)

  {

  TEntry& iEntry = (TEntry&)dir[i];

  TBufC<256> iFileName = iEntry.iName;

  }

  delete dir;

  dir = NULL;

  iAppContainer = new (ELeave) CCountEntryContainer;

  iAppContainer->SetMopParent( this );

  iAppContainer->ConstructL( ClientRect() );

  AddToStackL( iAppContainer );

  }

  通过设置断点进行观察,可以看到如下结果:

  遍历Symbian某目录下的所有文件

  而Symbian系统C盘下的文件内容如下:

  遍历Symbian某目录下的所有文件

  可见,此时程序所读取到的文件数目是正确的。

  ② 下面我们来看第二中获取Symbian某目录下所有文件的方法,其基本原理是类似的,只不过是调用了不同的接口而已。

  RFs iFs;

  User::LeaveIfError(iFs.Connect());

  _LIT(KDIR,"C:\\");

  RDir oDir;

  oDir.Open(iFs, KDIR, KEntryAttNormal);

  TEntryArray* oArray = new (ELeave) TEntryArray;

  oDir.Read(*oArray);

  TInt iCount = oArray->Count();

  for(TInt i = 0;i < iCount;i++)

  {

  TEntry temp = (*oArray)[i];

  TName iTemp = temp.iName;

  if(i == 2)

  CEikonEnv::Static()->InfoMsg(iTemp);

  }

  iFs.Close();

  和第一种方法不同的是,这里使用了RDir类作为目录项的存放数组。我们看看SDK HELP中这个类的帮助文档:

  RDir

  Support

  Supported from 5.0

  Description

  Reads the entries contained in a directory.

  读取一个目录中所包含的项,包括目录、文件以及驱动器卷标,这一点和上面的CDir类是一样的。

  You must first open the directory, specifying an attribute mask which is used by Read() calls to filter the entry types required. Then, use one of the Read() functions to read the filtered entries. When the operation is complete, the directory should be closed using Close(), defined in the base class RFsBase.

  你必须先打开目录,定义一个属性掩码用来过滤项类型。然后用Read()函数去读取过滤的项。当操作完成时,目录应该调用基类RFsBase中定义的Close()方法关闭。

  There are two types of Read(): one works with a single entry at a time, requiring programs to iterate through the entries explicitly. The other works with an entire TEntryArray, allowing multiple entries to be read in one call. As well as making application program logic somewhat simpler, this type uses fewer calls to the server, and is more efficient.

  有两种版本的Read()方法:一种是每次读取一个目录项,要求遍历所有目录项。另一种利用一个TEntryArray工作,它允许多个目录项一次读取完。为了让应用程序逻辑简单,这种类型和服务器的交互少,并且非常高效。

  Each type of Read() can be performed either synchronously or asynchronously.

  每种版本的Read()方法都可以表现为同步的或者异步的。

  It may be more convenient to use RFs::GetDir() than the Read() calls supported by this class. RFs::GetDir() has the advantage that it allows a directory's entries to be sorted in various ways. However, it does not provide asynchronous as well as synchronous variants and does not allow entries to be read individually.

  RFs::GetDir()比这个类所提供的方法更方便,而且RFs::GetDir()允许一个目录的项以不同的方式排序。尽管如此,RFs::GetDir()却不区分同步、异步的方式,并且不允许目录项逐个的读取。

  Derivation

  RSubSessionBase - Client-side handle to a sub-session

  RFsBase - Base class that provides a Close() function for file related clean-up

  RDir - Reads the entries contained in a directory

  Members

  Defined in RDir:

  Open(), Open(), Read(), Read(), Read(), Read()

  Inherited from RFsBase:

  Close()

  Inherited from RSubSessionBase:

  CloseSubSession(), CreateSubSession(), Send(), SendReceive(), SubSessionHandle(), operator=()

  看到这里,再和第一种方法进行比较,就应该很容易明白开头所给出的代码了,这段代码在VS2003+Carbide.vs+ S60_2nd_FP2_SC SDK中也编译通过.

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