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[操作系统]IOS 开发之文件管理


一、iOS中的沙盒机制

  • 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:(NSData *)Data dataUsingEncoding: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 = CFPropertyListCreateFrom    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"];                                       

将字符串转成NSData类型                                                                                

NSString *text = @"abcdefg"; 

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/NewTestament.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([fmfileExistsAtPath]){                                                                                                                   

if([fmremoveItemAtPath:copyPath]) {                                                                                                                   NSLog(@"removesuccess");

} }

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 = [dirEnumnextObject]} !=nil{                                                                                                                  NSLog(@"%@",path);

}