iOS开发-文件管理

• iOS应用程序只能对自己创建的文件系统读取文件，这个独立、封闭、安全的空间，叫做沙盒。它一般存放着程序包文件（可执行文件）、图片、音频、视频、plist文件、sqlite数据库以及其他文件。

• 每个应用程序都有自己的独立的存储空间（沙盒）

• 一般来说应用程序之间是不可以互相访问

模拟器沙盒的位置

/User/userName/Library/Application Support/iPhone Simulator

当我们创建应用程序时，在每个沙盒中含有三个文件，分别是Document、Library和temp。

• Document：一般需要持久的数据都放在此目录中，可以在当中添加子文件夹，iTunes备份和恢复的时候，会包括此目录。

• Library：设置程序的默认设置和其他状态信息

• temp：创建临时文件的目录，当iOS设备重启时，文件会被自动清除

获取沙盒目录

• 获取程序的根目录（home）目录

NSString *homePath = NSHomeDirectory()

• 获取Document目录

NSArray  *paths = NSSearchPathDorDirectoriesInDomains(NSDocumentDicrectory,, NSUserDomainMark, YES);   NSString *docPath = [paths lastObject];

• 获取Library目录

NSArray *paths = NSSearchPathForDirectoriseInDomains(NSLibraryDirectory, NSUserDomainMask, YES);  NSString *docPath = [paths lastObject];   

• 获取Library中的Cache

NSArray *paths = NSSearchPathForDirectoriseInDomains(NSCachesDirectory, NSUserDomainMask, YES);   NSString *docPath = [paths lastObject];

• 获取temp路径

NSString *temp = NSTemporaryDirectory( );

二、NSString类路径的处理方法

文件路径的处理

NSString *path = @"/Uesrs/apple/testfile.txt"

• 常用方法如下

获得组成此路径的各个组成部分，结果：（"/","User","apple","testfile.txt"）

- (NSArray *)pathComponents;

提取路径的最后一个组成部分，结果：testfile.txt

- (NSString *)lastPathComponent;

删除路径的最后一个组成部分，结果：/Users/apple

- (NSString *)stringByDeletingLastPathCpmponent;

将path添加到先邮路径的末尾，结果：/Users/apple/testfile.txt/app.txt

- (NSString *)stringByAppendingPathConmponent:(NSString *)str;

去路径最后部分的扩展名，结果：text

- (NSString *)pathExtension;

删除路径最后部分的扩展名，结果：/Users/apple/testfile

- (NSString *)stringByDeletingPathExtension;

路径最后部分追加扩展名，结果：/User/apple/testfile.txt.jpg

- (NSString *)stringByAppendingPathExtension:(NSString *)str;

三、NSData

• NSData是用来包装数据的

• NSData存储的是二进制数据，屏蔽了数据之间的差异，文本、音频、图像等数据都可用NSData来存储
  

NSData的用法

1.NSString与NSData互相转换

NSData－> NSString  NSString *aString = [[NSString alloc] initWithData:adataencoding:NSUTF8StringEncoding];

NSString－>NSData  NSString *aString = @"1234abcd";
NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding]; 

将data类型的数据,转成UTF8的数据

+(NSString *)dataToUTF8String:(NSData *)data
{
NSString *buf = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
return [buf autorelease];
}

将string转换为指定编码 
+(NSString *)changeDataToEncodinString:(NSData *)data encodin:(NSStringEncoding )encodin{
    NSString *buf = [[[NSString alloc] initWithData:data encoding:encodin] autorelease];
    return buf;
}

2. NSData 与 UIImage
NSData－>UIImage
UIImage *aimage = [UIImage imageWithData: imageData];
 
//例：从本地文件沙盒中取图片并转换为NSData
NSString *path = [[NSBundle mainBundle] bundlePath];
NSString *name = [NSString stringWithFormat:@"ceshi.png"];
NSString *finalPath = [path stringByAppendingPathComponent:name];
NSData *imageData = [NSData dataWithContentsOfFile: finalPath];
UIImage *aimage = [UIImage imageWithData: imageData];

3.NSData与NSArray  NSDictionary

+(NSString *)getLocalFilePath:(NSString *) fileName
{
return [NSString stringWithFormat:@"%@/%@%@", NSHomeDirectory(),@“Documents”,fileName];
}

包括将NSData写进Documents目录
从Documents目录读取数据
在进行网络数据通信的时候，经常会遇到NSData类型的数据。在该数据是dictionary结构的情况下，系统没有提供现成的转换成NSDictionary的方法，为此可以通过Category对NSDictionary进行扩展，以支持从NSData到NSDictionary的转换。声明和实现如下：
 
+ (NSDictionary *)dictionaryWithContentsOfData:(NSData *)data {     
    CFPropertyListRef list = CFPropertyListCreateFromXMLData(kCFAllocatorDefault, (CFDataRef)data, kCFPropertyListImmutable, NULL);
    if(list == nil) return nil; 
    if ([(id)list isKindOfClass:[NSDictionary class]]) { 
         return [(NSDictionary *)list autorelease]; 
        } 
    else { 
         CFRelease(list); 
         return nil; 
        } 
}

四、文件管理常用方法

NSFileManager

创建一个文件并写入数据 

 - (BOOL)createFileAtPath:(NSString *)path contents:(NSData *)data attributes:(NSDictionary *)attr;

从一个文件中读取数据     

- (NSData *)contentsAtPath:(NSString *)path;

scrPath路径上的文件移动到dstPath路径上，注意这里的路径是文件路径而不是目录 

 - (BOOL)moveItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **) error;

scrPath路径上的文件复制到dstPath路径上 

 - (BOOL)copyItemAtPath:(NSString *)scrPath toPath:(NSString *)dstPath error:(NSError **) error;

比较两个文件的内容是否一样  

- (BOOL)contentsEqualAtPath:(NSString *)path1 andPath:(NSString *)path2;

文件时候存在 

   - (BOOL)fileExistsAtPath:(NSString *)path;

移除文件 

 - (BOOL)removeItemAtPath:(NSString *)path error:(NSError **) error;

创建文件管理

NSFileManager *fileManager = [NSFileManager defaultManager];

 NSString *path = [NSHomeDirectory( )  stringByAppendingPathComponent:@"holyBible.txt"];    

NSString *text = @"abcdefg"; 

将字符串转成NSData类型 

 NSData *data = [text dataUsingEncoding: NSUTF8StringEncoding]; 

写入文件 

BOOL success = [fileManager createFileAtPath:path contents:data attributes:nil];

创建文件夹 

NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];    

NSString *contect = @"abcdefg";                                                                    

BOOL success = [fm createFileAtPath:filePath contents:[content dataUsingEncoding: NSUTF8StringEncoding] attributes:nil];

NSFileManager-读取内容                                                                                

NSData *fileData = [fileManager contentsAtPath:filePath];                                  

NSString *content = [[NSString alloc] initWithData:fileData dataUsingEncoding: NSUTF8StringEncoding];

NSData-读取内容                                                                                          

NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];    

NSData *data = [NSData dataWithContentOfFile:filePath];

NSString-读取内容                                                                                        

NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];    

NSString *content = [[NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];

移动、复制文件                                                                                             

移动文件（重命名）                                                                                         

NSString *toPath = [NSHomeDirectory( ) stringByAppendingPathComponent:@"hellogod/New Testament.txt"];                                                                             

 [fm createDirectoryAtPath:[toPath stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:nil];                                                 

  NSError *error;                                                                                            

BOOL isSuccess = [fm moveItemAtPath:filePath toPath:toPath error:&error];

复制文件（重命名）                                                                                        

NSString *copyPath = [NSHomeDirectory( ) stringByAppendingPathComponent:@"备份/Old Testament.txt"];                                                                                 

 [fm createDirectoryAtPath:[toPath stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:nil];                                                  

BOOL success = [fm copyItemAtPath:toPath toPath:toPath error:nil];

删除文件、获取文件大小

判断文件是否存在和删除文件                                                                             

  if([fm fileExistsAtPath])                                                                                    

 {                                                                                                                   

if ([fm removeItemAtPath:copyPath])                                                               

 {                                                                                                                  

NSLog(@"remove success");                                                                            

}                                                                                                                  

}

获取文件大小                                                                                                 

 NSFileManager *fileManager = [NSFileManager defaultManager];                        

 获得文件的属性字典                                                                                        

NSDictionary *attrDic = [fileManager attributesOfItemAtpath:sourcePath error:nil]; 

NSNumber *fileSize = [attrDic objectForKey:NSFileSize];   

获取目录文件信息                                                                                            

NSFileManager *fileManager = [NSFileManager defaultManager];                        

NSString *enuPath = [NSHomeDirectoty( ) stringByAppendingPathComponent:@"Test"];                                                                                                          

NSDictionaryEnumerator *dirEnum = [fileManager enumeratorAtPath:enuPath];    

NSString *path = nil;                                                                                     

while ((path = [dirEnum nextObject]} != nil)                                                        

{                                                                                                                 

NSLog(@"%@",path);                                                                                        

}

五、Plist文件

String方式添加              

NSString *path = [NSHomeDirectory( )  stringByAppendingPathComponent:@"Array.plist"];                    

NSString *content = @"abcd";            

[contect writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:nil];

Array方式添加        

NSString *path = [NSHomeDirectory( )  stringByAppendingPathComponent:@"Array.plist"];     

[NSArray *array = [[NSArray alloc] initWithObjects:@"123", @"798"，@"000",nil];      

 [array writeToFile:path atomically:YES];

Dictionary方式添加          

NSString *path = [NSHomeDirectory( )  stringByAppendingPathComponent:@"Dic.plist"];                        

NSDictionary *dic = [NSDictionary alloc] initWithObjects:@"first",@"second",@"third"forKeys:@"123",@"456",@"798"];                                                                      

 [dic writeToFile:path atomically:YES];

• 数组、字典只能将BOOL、NSNumber、NSString、NSData、NSDate、NSArray、NSDictionary写入属性列表plist文件

六、读取文件类和常用方法

• NSFileHandle类主要对文件内容进行读取和写入操作

• NSFileManager类主要对文件的操作（删除、修改、移动、复制等等）

常用处理方法

+ (id)fileHandleForReadingAtPath:(NSString *)path  打开一个文件准备读取     

+ (id)fileHandleForWritingAtPath:(NSString *)path  打开一个文件准备写入   

+ (id)fileHandleForUpdatingAtPath:(NSString *)path  打开一个文件准备更新  

-  (NSData *)availableData; 从设备或通道返回可用的数据            

-  (NSData *)readDataToEndOfFile; 从当前的节点读取到文件的末尾               

-  (NSData *)readDataOfLength:(NSUInteger)length; 从当前节点开始读取指定的长度数据                           

-  (void)writeData:(NSData *)data; 写入数据         

-  (unsigned long long)offsetInFile;  获取当前文件的偏移量            

-  (void)seekToFileOffset:(unsigned long long)offset; 跳到指定文件的偏移量     

-  (unsigned long long)seekToEndOfFile; 跳到文件末尾        

-  (void)truncateFileAtOffset:(unsigned long long)offset; 将文件的长度设为offset字节

-  (void)closeFile;  关闭文件

向文件追加数据

NSString *homePath  = NSHomeDirectory( );        

NSString *sourcePath = [homePath stringByAppendingPathConmpone:@"testfile.text"];                                            

NSFileHandle *fielHandle = [NSFileHandle fileHandleForUpdatingAtPath:sourcePath];                                                        

[fileHandle seekToEndOfFile];  将节点跳到文件的末尾          

NSString *str = @"追加的数据"                   

NSData* stringData  = [str dataUsingEncoding:NSUTF8StringEncoding];          

[fileHandle writeData:stringData]; 追加写入数据       

[fileHandle closeFile];

定位数据                    

NSFileManager *fm = [NSFileManager defaultManager];              

NSString *content = @"abcdef";                      

[fm createFileAtPath:path contents:[content dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];                                                   

NSFileHandle *fileHandle = [NSFileHandle fileHandleForReadingAtPath:path];      

NSUInteger length = [fileHandle availabelData] length]; 获取数据长度       

[fileHandle seekToFileOffset;length/2]; 偏移量文件的一半           

NSData *data = [fileHandle readDataToEndOfFile];                

[fileHandle closeFile];

复制文件                           

NSFileHandle *infile, *outfile; 输入文件、输出文件          

NSData *buffer; 读取的缓冲数据                    

NSFileManager *fileManager = [NSFileManager defaultManager];   

NSString *homePath = NSHomeDirectory( );              

NSString *sourcePath = [homePath stringByAppendingPathComponent:@"testfile.txt"];  源文件路径                                          

NSString *outPath = [homePath stringByAppendingPathComponent:@"outfile.txt"]; 输出文件路径                               

BOOL sucess  = [fileManager createFileAtPath:outPath contents:nil attributes:nil];  

if (!success)          

{                                                      

return N0;                                                                                                   

}                 

infile = [NSFileHandle fileHandleForReadingAtPath:sourcePath]; 创建读取源路径文件

if (infile == nil)                          

{                                          

return NO;                      

}                           

outfile = [NSFileHandle fileHandleForReadingAtPath:outPath]; 创建病打开要输出的文件                                                                                                                

if (outfile == nil)                            

{                                                               

return NO;                                                    

}                                             

[outfile truncateFileAtOffset:0]; 将输出文件的长度设为0         

buffer = [infile readDataToEndOfFile];  读取数据           

[outfile writeData:buffer];  写入输入                        

[infile closeFile];        关闭写入、输入文件               

[outfile closeFile]；