完成效果：

用iTunes向app匯入視訊後，不用手動重新整理，編寫的工具類會實時監聽複製狀態，複製完成後會自動重新整理UI.

大坑：因為檔案共享是共享的Document資料夾下所有資源，所以你需要把非共享的檔案，如：資料庫檔案、快取檔案等，存放到除Document資料夾以外的地方，如：Preferences或Caches資料夾下，否則app會被拒！！！

1.在Info.plist新增欄位:

“Application supports iTunes file sharing” 值設定為“YES”;
新增之後手機連線iTunes才能在檔案共享中找到自己的應用

2.單例工具類FileWatcher

的啟動與登出

啟動內容包括：
* 獲取app中已經用iTunes匯入的視訊
* 開啟對Document資料夾的監聽
* 相關屬性的初始化

@interface FileWatcher ()
@property (nonatomic, strong)  dispatch_source_t source;
@property (nonatomic, strong) NSMutableArray *videoNameArr;
@property (nonatomic, assign) BOOL isConvenientFinished; //一次遍歷完成標識
@property (nonatomic
 
, assign) BOOL isFinishedCopy; //複製完成標識
@end

- (void)startManager {
    self.dataSource = [[NSMutableArray alloc] init];
    self.videoNameArr = [[NSMutableArray alloc] init];
    self.isFinishedCopy = YES;  
    self.isConvenientFinished = YES;
    [self getiTunesVideo];
    [self startMonitorFile];
}

- (void
 
)stopManager {
    dispatch_cancel(self.source);
}

3.Document資料夾監聽方法

- (void)startMonitorFile {  //監聽Document資料夾的變化

    NSURL *directoryURL = [NSURL URLWithString:[SandBoxHelper docPath]]; //新增需要監聽的目錄    
    int const fd =
    open([[directoryURL path] fileSystemRepresentation], O_EVTONLY);
    if (fd < 0) {     
        NSLog(@"Unable to open the path = %@", [directoryURL path]);
        return;
    }    
    dispatch_source_t source =
    dispatch_source_create(DISPATCH_SOURCE_TYPE_VNODE, fd,
                           DISPATCH_VNODE_WRITE,
                           DISPATCH_TARGET_QUEUE_DEFAULT);
    dispatch_source_set_event_handler(source, ^() {
        unsigned long const type = dispatch_source_get_data(source);
        switch (type) {
            case DISPATCH_VNODE_WRITE: {
                NSLog(@"Document目錄內容發生變化!!!");
                if (self.isConvenientFinished) {
                    self.isConvenientFinished = NO;
                    [self directoryDidChange];
                }
                break;
            }
            default:
                break;
        }
    });

    dispatch_source_set_cancel_handler(source, ^{
        close(fd);        
    });    
    self.source = source;
    dispatch_resume(self.source);
}

4.將iTunes匯入的視訊顯示出來的核心方法

- (void)directoryDidChange {
    [self getiTunesVideo];
}

- (void)getiTunesVideo {    
    dispatch_async(fileWatcher_queue(), ^{
        //獲取沙盒裡所有檔案
        NSFileManager *fileManager = [NSFileManager defaultManager];
        //在這裡獲取應用程式Documents資料夾裡的檔案及資料夾列表
        NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentDir = [documentPaths objectAtIndex:0];
        NSError *error = nil;
        NSArray *fileList = [[NSArray alloc] init];
        //fileList便是包含有該資料夾下所有檔案的檔名及資料夾名的陣列
        fileList = [fileManager contentsOfDirectoryAtPath:documentDir error:&error];
        if (fileList.count > 0) {
            for (NSString *file in fileList) {
                //在這裡新增資源的過濾條件
                if ([file hasSuffix:@".mov"] ||[file hasSuffix:@".mp4"] || [file hasSuffix:@".m4v"]) {
                    NSString *videoPath = [documentDir stringByAppendingPathComponent:file];
                    NSArray *lyricArr = [videoPath componentsSeparatedByString:@"/"];
                   //此判斷的作用：避免同一資源的反覆新增，使資源只新增過一次後，只要不刪，就不會再重新獲取路徑、圖片等
                    if (![self.videoNameArr containsObject:[lyricArr lastObject]]) {
                        [self.videoNameArr addObject:[lyricArr lastObject]];
                        //===============================迴圈判斷是否複製完成==============================================
                        NSInteger lastSize = 0;
                        NSDictionary *fileAttrs = [[NSFileManager defaultManager] attributesOfItemAtPath:videoPath error:nil];
                        NSInteger fileSize = [[fileAttrs objectForKey:NSFileSize] intValue];
                        do {
                            lastSize = fileSize;
                            [NSThread sleepForTimeInterval:0.5];
                            self.isFinishedCopy = NO;
                            fileAttrs = [[NSFileManager defaultManager] attributesOfItemAtPath:videoPath error:nil];
                            fileSize = [[fileAttrs objectForKey:NSFileSize] intValue];
                            NSLog(@"%@檔案正在複製", [lyricArr lastObject]);
                        } while (lastSize != fileSize);
                        self.isFinishedCopy = YES;
                        NSLog(@"%@檔案複製完成", [lyricArr lastObject]);
                        VideoModel *model = [[VideoModel alloc] init];
                        model.videoPath = videoPath;
                        model.videoName = [lyricArr lastObject];
                        model.videoSize = [SandBoxHelper fileSizeForPath:videoPath];
                        model.videoImgPath = [self saveImg:[UIImage getThumbnailImage:videoPath] withVideoMid:[NSString stringWithFormat:@"%lld", model.videoSize]];
                        model.videoAsset = nil;
                        [self.dataSource addObject:model];
                        ///為防止一次同時拖入多個文件，使得資料載入不全，特做一次遞迴處理。
                        [self directoryDidChange];
                    }
                    [[NSNotificationCenter defaultCenter] postNotificationName:RefreshiTunesUINotification object:nil];
                }
            }
        }
        self.isConvenientFinished = YES;
    });
}

4.1.拿到匯入視訊的縮圖，並存到本地

+(UIImage *)getThumbnailImage:(NSString *)videoURL {    
    if (videoURL) {
        AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:videoURL] options:nil];       
        AVAssetImageGenerator *gen = [[AVAssetImageGenerator alloc] initWithAsset:asset];        
        // 設定縮圖的方向
        // 如果不設定，可能會在視訊旋轉90/180/270°時，獲取到的縮圖是被旋轉過的，而不是正向的
        gen.appliesPreferredTrackTransform = YES;    
        // 設定圖片的最大size(解析度)
        gen.maximumSize = CGSizeMake(300, 169);       
        CMTime time = CMTimeMakeWithSeconds(5.0, 600); //一秒鐘600幀，取第10幀。
        NSError *error = nil;
        CMTime actualTime; 
        CGImageRef image = [gen copyCGImageAtTime:time actualTime:&actualTime error:&error];    
        if (error) {
            UIImage *placeHoldImg = [UIImage imageNamed:@"posters_default_horizontal"];
            return placeHoldImg;
        }  
        UIImage *thumb = [[UIImage alloc] initWithCGImage:image];  
        CGImageRelease(image);   
        return thumb;      
    } else { 
         UIImage *placeHoldImg = [UIImage imageNamed:@"posters_default_horizontal"];
        return placeHoldImg;
    }
}

- (NSString *)saveImg:(UIImage *)image withVideoMid:(NSString *)videoMid{  
    if (!image) {
        image = [UIImage imageNamed:@"posters_default_horizontal"];
    }
    if (!videoMid) {
        videoMid = [NSString uuid];
    }
    //png格式
    NSData *imagedata=UIImagePNGRepresentation(image); 
    NSString *savedImagePath = [[SandBoxHelper iTunesVideoImagePath] stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", videoMid]];
    [imagedata writeToFile:savedImagePath atomically:YES];  
    return savedImagePath;    
}

5.刪除檔案

- (void)deleteiTunesVideo:(NSArray *)array {
    for (VideoModel *item in array) {
        [self.dataSource removeObject:item];
        [SandBoxHelper deleteFile:item.videoPath];
        [SandBoxHelper deleteFile:item.videoImgPath];
        [self.videoNameArr removeObject:item.videoName];
    }
}

以上為檔案共享的開發步驟，關於如何使用封裝好的工具類，請參考程式碼