1.添加属性

@property (nonatomic, strong)  dispatch_source_t source;

2.开启监听

- (void)startManager {
    [self startMonitorFile];
}

- (void)startMonitorFile {  //监听Document文件夹的变化
    NSURL *directoryURL = [NSURL URLWithString:[SandBoxHelper docPath]]; //添加需要监听的目录
    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: {
                PVRLog(@"Document目录内容发生变化!!!");
                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);
}

3.在退出的时候,注销一下

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