需求：點擊按鈕，彈出ActionSheet提示框，可選擇從相冊中選取圖片或者拍照，選擇成功后的照片顯示在按鈕上

1 按鈕的點擊事件

 func topPictureBtnClick(){
     self.choosePictureAlert()
 }

2 彈出提示框

 func choosePictureAlert(){
        var alert: UIAlertController!
        alert = UIAlertController(title: "\(alertTitle!)", message: "", preferredStyle: UIAlertControllerStyle.actionSheet)
        let cleanAction = UIAlertAction(title: "取消", style: UIAlertActionStyle.cancel,handler:nil)
        let photoAction = UIAlertAction(title: "拍照", style: UIAlertActionStyle.default){ (action:UIAlertAction)in
            self.openCamera()
        }
        let choseAction = UIAlertAction(title: "相冊", style: UIAlertActionStyle.default){ (action:UIAlertAction)in
            self.takePhoto()
        }
        alert.addAction(cleanAction)
        alert.addAction(photoAction)
        alert.addAction(choseAction)
        DispatchQueue.main.async {
            self.present(alert, animated: true, completion: nil)
        }
   } 

3 打開相機方法

    //打開相機
    func openCamera()
    {
        //判斷設置是否支持圖片庫
        if UIImagePickerController.isSourceTypeAvailable(.camera){
            //初始化圖片控制器
            let picker = UIImagePickerController()
            //設置代理
            picker.delegate = self
            //指定圖片控制器類型
            picker.sourceType = UIImagePickerControllerSourceType.camera
            //彈出控制器，顯示界面
            self.present(picker, animated: true, completion: {
                () -> Void in
            })
        }else{
            print("讀取相機錯誤")
        }
    }

4 打開相冊方法

    func takePhoto()
    {
        //判斷設置是否支持圖片庫
        if UIImagePickerController.isSourceTypeAvailable(.photoLibrary){
            //初始化圖片控制器
            let picker = UIImagePickerController()
            //設置代理
            picker.delegate = self
            //指定圖片控制器類型
            picker.sourceType = UIImagePickerControllerSourceType.photoLibrary
            //picker.mediaTypes = UIImagePickerController.availableMediaTypes(for: .photoLibrary)!
            picker.videoMaximumDuration = 10
            //彈出控制器，顯示界面
            self.present(picker, animated: true, completion: {
                () -> Void in
            })
        } else {
            print("讀取相冊錯誤")
        }
    }

6 選擇相冊成功的代理方法

   // 選擇圖片成功后代理
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
        print(info)
       // 得到 UIImage 類型的照片 
        btnImage = info[UIImagePickerControllerOriginalImage]as!UIImage
       // 照片顯示在按鈕上（當在代理方法中無法傳值的時候,設置全局變量，進行傳值）
        self.currentBtn.setBackgroundImage(btnImage, for: .normal)
        picker.dismiss(animated:true, completion:nil)
    }