-(void) screenShot{

  UIGraphicsBeginImageContext(self.bounds.size);   //self為需要截屏的UI控件 即通過改變此參數可以截取特定的UI控件 
  [self.layer renderInContext:UIGraphicsGetCurrentContext()];    
  UIImage *image= UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();    
  NSLog(@"image:%@",image); //至此已拿到image

  UIImageView *imaView = [[UIImageView alloc] initWithImage:image];   
  imaView.frame = CGRectMake(0, 700, 500, 500);    
  [self addSubview:imaView];    

  UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);//把圖片保存在本地
}
// 調用最后一行代碼的時候需要在plist中添加這行代碼：Privacy - Photo Library Usage Description