//截屏
static int i=0;
-(IBAction)screenShot:(id)sender{
    
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(640, 960), YES, 0);
    [[self.window layer] renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGImageRef imageRef = viewImage.CGImage;
    CGRect rect =CGRectMake(166, 211, 426, 320);//這裡可以設置想要截圖的區域
    CGImageRef imageRefRect =CGImageCreateWithImageInRect(imageRef, rect);
    UIImage *sendImage = [[UIImage alloc] initWithCGImage:imageRefRect];
    UIImageWriteToSavedPhotosAlbum(sendImage, nil, nil, nil);//保存圖片到照片庫
    NSData *imageViewData = UIImagePNGRepresentation(sendImage);
    
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *pictureName= [NSString stringWithFormat:@"screenShow_%d.png",i];
    NSString *savedImagePath = [documentsDirectory stringByAppendingPathComponent:pictureName];
    NSLog(@"%@", savedImagePath);
    [imageViewData writeToFile:savedImagePath atomically:YES];//保存照片到沙盒目錄
    CGImageRelease(imageRefRect);
    i++;
}