- (void)viewDidLoad {
    [super viewDidLoad];

    [NSTimer scheduledTimerWithTimeInterval:2
                                     target:self
                                   selector:@selector(updateDataMethod:)
                                   userInfo:nil
                                    repeats:YES];


}

-(void)updateDataMethod:(NSTimer*)timer {

    UIGraphicsBeginImageContextWithOptions(CGSizeMake(640, 960), YES, 0);
    [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGImageRef imageRef = viewImage.CGImage;
    CGRect rect =self.view.bounds;//这里可以设置想要截图的区域
    CGImageRef imageRefRect =CGImageCreateWithImageInRect(imageRef, rect);
    UIImage *sendImage = [[UIImage alloc] initWithCGImage:imageRefRect];
    NSData *imageViewData = UIImagePNGRepresentation(sendImage);

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *savedImagePath = [documentsDirectory stringByAppendingPathComponent:@"result.png"];
    NSLog(@"%@", savedImagePath);
    [imageViewData writeToFile:savedImagePath atomically:YES];
    CGImageRelease(imageRefRect);
}