iOS開發-文件管理

一、iOS中的沙盒機制

• iOS應用程序只能對自己創建的文件系統讀取文件，這個獨立、封閉、安全的空間，叫做沙盒。它一般存放著程序包文件（可執行文件）、圖片、音頻、視頻、plist文件、sqlite數據庫以及其他文件。

• 每個應用程序都有自己的獨立的存儲空間（沙盒）

• 一般來說應用程序之間是不可以互相訪問

模擬器沙盒的位置

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

當我們創建應用程序時，在每個沙盒中含有三個文件，分別是Document、Library和temp。

• Document：一般需要持久的數據都放在此目錄中，可以在當中添加子文件夾，iTunes備份和恢復的時候，會包括此目錄。

• Library：設置程序的默認設置和其他狀態信息

• temp：創建臨時文件的目錄，當iOS設備重啟時，文件會被自動清除

獲取沙盒目錄

• 獲取程序的根目錄（home）目錄

NSString *homePath = NSHomeDirectory()

• 獲取Document目錄

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

• 獲取Library目錄

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

• 獲取Library中的Cache

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

• 獲取temp路徑

NSString *temp = NSTemporaryDirectory( );

二、NSString類路徑的處理方法

文件路徑的處理

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

• 常用方法如下

獲得組成此路徑的各個組成部分，結果：（"/","User","apple","testfile.txt"）

- (NSArray *)pathComponents;

提取路徑的最后一個組成部分，結果：testfile.txt

- (NSString *)lastPathComponent;

刪除路徑的最后一個組成部分，結果：/Users/apple

- (NSString *)stringByDeletingLastPathCpmponent;

將path添加到先郵路徑的末尾，結果：/Users/apple/testfile.txt/app.txt

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

去路徑最后部分的擴展名，結果：text

- (NSString *)pathExtension;

刪除路徑最后部分的擴展名，結果：/Users/apple/testfile

- (NSString *)stringByDeletingPathExtension;

路徑最后部分追加擴展名，結果：/User/apple/testfile.txt.jpg

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

三、NSData

• NSData是用來包裝數據的

• NSData存儲的是二進制數據，屏蔽了數據之間的差異，文本、音頻、圖像等數據都可用NSData來存儲
  

NSData的用法

1.NSString與NSData互相轉換

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

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

將data類型的數據,轉成UTF8的數據

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

將string轉換為指定編碼 
+(NSString *)changeDataToEncodinString:(NSData *)data encodin:(NSStringEncoding )encodin{
    NSString *buf = [[[NSString alloc] initWithData:data encoding:encodin] autorelease];
    return buf;
}

2. NSData 與 UIImage
NSData－>UIImage
UIImage *ap_w_picpath = [UIImage p_w_picpathWithData: p_w_picpathData];
 
//例：從本地文件沙盒中取圖片并轉換為NSData
NSString *path = [[NSBundle mainBundle] bundlePath];
NSString *name = [NSString stringWithFormat:@"ceshi.png"];
NSString *finalPath = [path stringByAppendingPathComponent:name];
NSData *p_w_picpathData = [NSData dataWithContentsOfFile: finalPath];
UIImage *ap_w_picpath = [UIImage p_w_picpathWithData: p_w_picpathData];

3.NSData與NSArray  NSDictionary

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

包括將NSData寫進Documents目錄
從Documents目錄讀取數據
在進行網絡數據通信的時候，經常會遇到NSData類型的數據。在該數據是dictionary結構的情況下，系統沒有提供現成的轉換成NSDictionary的方法，為此可以通過Category對NSDictionary進行擴展，以支持從NSData到NSDictionary的轉換。聲明和實現如下：
 
+ (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

創建一個文件并寫入數據                                                                                    - (BOOL)createFileAtPath:(NSString *)path contents:(NSData *)data attributes:(NSDictionary *)attr;

從一個文件中讀取數據                                                                                       - (NSData *)contentsAtPath:(NSString *)path;

scrPath路徑上的文件移動到dstPath路徑上，注意這里的路徑是文件路徑而不是目錄          - (BOOL)moveItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **) error;

scrPath路徑上的文件復制到dstPath路徑上                                                            - (BOOL)copyItemAtPath:(NSString *)scrPath toPath:(NSString *)dstPath error:(NSError **) error;

比較兩個文件的內容是否一樣                                                                               - (BOOL)contentsEqualAtPath:(NSString *)path2 andPath:(NSString *)path3;

文件時候存在                                                                                                  - (BOOL)fileExistsAtPath:(NSString *)path;

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

創建文件管理

NSFileManager *fileManager = [NSFileManager defaultManager];                          NSString *path = [NSHomeDirectory( )  stringByAppendingPathComponent:@"holyBible.txt"];                                                                                                     NSString *text = @"abcdefg"; 

將字符串轉成NSData類型                                                                                 NSData *data = [text dataUsingEncoding: NSUTF8StringEncoding]; 

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

創建文件夾 

NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];     NSString *contect = @"abcdefg";                                                                     BOOL success = [fm createFileAtPath:filePath contents:[content dataUsingEncoding: NSUTF8StringEncoding] attributes:nil];

NSFileManager-讀取內容                                                                                 NSData *fileData = [fileManager contentsAtPath:filePath];                                   NSString *content = [[NSString alloc] initWithData:fileData dataUsingEncoding: NSUTF8StringEncoding];

NSData-讀取內容                                                                                          NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];     NSData *data = [NSData dataWithContentOfFile:filePath];

NSString-讀取內容                                                                                         NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];     NSString *content = [[NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];

移動、復制文件                                                                                             

移動文件（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];

復制文件（重命名）                                                                                         NSString *copyPath = [NSHomeDirectory( ) stringByAppendingPathComponent:@"備份/Old Testament.txt"];                                                                                  [fm createDirectoryAtPath:[toPath stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:nil];                                                   BOOL success = [fm copyItemAtPath:toPath toPath:toPath error:nil];

刪除文件、獲取文件大小

判斷文件是否存在和刪除文件                                                                               if([fm fileExistsAtPath])                                                                                     {                                                                                                                    if ([fm removeItemAtPath:copyPath])                                                                {                                                                                                                   NSLog(@"remove success");                                                                            }                                                                                                                  }

獲取文件大小                                                                                                  NSFileManager *fileManager = [NSFileManager defaultManager];                         獲得文件的屬性字典                                                                                         NSDictionary *attrDic = [fileManager attributesOfItemAtpath:sourcePath error:nil];  NSNumber *fileSize = [attrDic objectForKey:NSFileSize];   

獲取目錄文件信息                                                                                            NSFileManager *fileManager = [NSFileManager defaultManager];                         NSString *enuPath = [NSHomeDirectoty( ) stringByAppendingPathComponent:@"Test"];                                                                                                           NSDictionaryEnumerator *dirEnum = [fileManager enumeratorAtPath:enuPath];     NSString *path = nil;                                                                                      while ((path = [dirEnum nextObject]} != nil)                                                        {                                                                                                                  NSLog(@"%@",path);                                                                                        }