iOS的沙盒机制。应用仅仅能訪问自己应用文件夹下的文件。iOS不像android。没有SD 卡概念。不能直接訪问图像、视频等内容。

iOS应用产生的内容，如图像、文件、缓存内容等都必须存储在自己的沙盒内。默认情况下，每一个沙盒含有3个文件 夹：Documents, Library 和 tmp。

Library包括Caches、Preferences文件夹。 Documents：苹果建议将程序创建产生的文件以及应用浏览产生的文件数据保存在该文件夹下，iTunes备份和恢复的时候会包括此文件夹 Library：存储程序的默认设置或其他状态信息； Library/Caches：存放缓存文件，保存应用的持久化数据。用于应用升级或者应用关闭后的数据保存，不会被itunes同步，所以为了降低同步的时间，能够考虑将一些比較大的文件而又不须要备份的文件放到这个文件夹下。 tmp：提供一个即时创建暂时文件的地方，但不须要持久化。在应用关闭后，该文件夹下的数据将删除。也可能系统在程序不执行的时候清除。 a:获取应用沙盒根路径： -(void)dirHome{ NSString *dirHome=NSHomeDirectory(); NSLog(@"app_home: %@",dirHome); } b:获取Documents文件夹路径： -(NSString *)dirDoc{ //[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"]; NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSLog(@"app_home_doc: %@",documentsDirectory); return documentsDirectory; } c:获取Library文件夹路径： -(void)dirLib{ //[NSHomeDirectory() stringByAppendingPathComponent:@"Library"]; NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES); NSString *libraryDirectory = [paths objectAtIndex:0]; NSLog(@"app_home_lib: %@",libraryDirectory); } d:获取Cache文件夹路径： -(void)dirCache{ NSArray *cacPath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); NSString *cachePath = [cacPath objectAtIndex:0]; NSLog(@"app_home_lib_cache: %@",cachePath); } e:获取Tmp文件夹路径： -(void)dirTmp{ //[NSHomeDirectory() stringByAppendingPathComponent:@"tmp"]; NSString *tmpDirectory = NSTemporaryDirectory(); NSLog(@"app_home_tmp: %@",tmpDirectory); } f:创建文件夹： -(void *)createDir{ NSString *documentsPath =[self dirDoc]; NSFileManager *fileManager = [NSFileManager defaultManager]; NSString *testDirectory = [documentsPath stringByAppendingPathComponent:@"test"]; // 创建文件夹 BOOL res=[fileManager createDirectoryAtPath:testDirectory withIntermediateDirectories:YES attributes:nil error:nil]; if (res) { NSLog(@"文件夹创建成功"); }else NSLog(@"文件夹创建失败"); } g:创建文件 -(void *)createFile{ NSString *documentsPath =[self dirDoc]; NSString *testDirectory = [documentsPath stringByAppendingPathComponent:@"test"]; NSFileManager *fileManager = [NSFileManager defaultManager]; NSString *testPath = [testDirectory stringByAppendingPathComponent:@"test.txt"]; BOOL res=[fileManager createFileAtPath:testPath contents:nil attributes:nil]; if (res) { NSLog(@"文件创建成功: %@" ,testPath); }else NSLog(@"文件创建失败"); } h:写数据到文件： -(void)writeFile{ NSString *documentsPath =[self dirDoc]; NSString *testDirectory = [documentsPath stringByAppendingPathComponent:@"test"]; NSString *testPath = [testDirectory stringByAppendingPathComponent:@"test.txt"]; NSString *content=@"測试写入内容！"; BOOL res=[content writeToFile:testPath atomically:YES encoding:NSUTF8StringEncoding error:nil]; if (res) { NSLog(@"文件写入成功"); }else NSLog(@"文件写入失败"); } i:读文件数据： -(void)readFile{ NSString *documentsPath =[self dirDoc]; NSString *testDirectory = [documentsPath stringByAppendingPathComponent:@"test"]; NSString *testPath = [testDirectory stringByAppendingPathComponent:@"test.txt"]; // NSData *data = [NSData dataWithContentsOfFile:testPath]; // NSLog(@"文件读取成功: %@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]); NSString *content=[NSString stringWithContentsOfFile:testPath encoding:NSUTF8StringEncoding error:nil]; NSLog(@"文件读取成功: %@",content); } j:文件属性： -(void)fileAttriutes{ NSString *documentsPath =[self dirDoc]; NSString *testDirectory = [documentsPath stringByAppendingPathComponent:@"test"]; NSFileManager *fileManager = [NSFileManager defaultManager]; NSString *testPath = [testDirectory stringByAppendingPathComponent:@"test.txt"]; NSDictionary *fileAttributes = [fileManager attributesOfItemAtPath:testPath error:nil]; NSArray *keys; id key, value; keys = [fileAttributes allKeys]; int count = [keys count]; for (int i = 0; i < count; i++) { key = [keys objectAtIndex: i]; value = [fileAttributes objectForKey: key]; NSLog (@"Key: %@ for value: %@", key, value); } } k:删除文件： -(void)deleteFile{ NSString *documentsPath =[self dirDoc]; NSString *testDirectory = [documentsPath stringByAppendingPathComponent:@"test"]; NSFileManager *fileManager = [NSFileManager defaultManager]; NSString *testPath = [testDirectory stringByAppendingPathComponent:@"test.txt"]; BOOL res=[fileManager removeItemAtPath:testPath error:nil]; if (res) { NSLog(@"文件删除成功"); }else NSLog(@"文件删除失败"); NSLog(@"文件是否存在: %@",[fileManager isExecutableFileAtPath:testPath]?@"YES":@"NO"); }