//先设定sourceType为相机，然后判断相机是否可用（ipod）没相机，不可用将sourceType设定为相片库
            UIImagePickerControllerSourceType sourceType = UIImagePickerControllerSourceTypeCamera;
                if (![UIImagePickerController isSourceTypeAvailable: UIImagePickerControllerSourceTypeCamera]) {
                    sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
                }
            //sourceType = UIImagePickerControllerSourceTypeCamera; //照相机
            //sourceType = UIImagePickerControllerSourceTypePhotoLibrary; //图片库
            //sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum; //保存的相片
            UIImagePickerController *picker = [[UIImagePickerController alloc] init];//初始化
            picker.delegate = self;
            picker.allowsEditing = YES;//设置可编辑
            picker.sourceType = sourceType;
            [self presentViewController:picker animated:YES completion:^{
                
            }];