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   源码介绍

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//
//  ViewController.swift
//  Food
//
//  Created by Aida on 2016/12/14.
//  Copyright © 2016年 Aida. All rights reserved.
//

import UIKit

class ViewController: UIViewController ,UITextFieldDelegate,UIImagePickerControllerDelegate,UINavigationControllerDelegate{

    @IBOutlet weak var nameText: UITextField!
    
    @IBOutlet weak var photoImg: UIImageView!
    
    @IBOutlet weak var ratingControl: RatingControl!
    @IBOutlet weak var saveOutlet: UIBarButtonItem!
    
    var meal:Meal?
    override func viewDidLoad() {
        super.viewDidLoad()
        self.nameText.delegate = self
        
        //由于修改和新增都是这个页面
        //当新增时，meal对象为nil自动跳过以下代码段
        //当修改时，meal对象在前一个页面已赋值，将数据取出在页面显示
        if let mealToEdit = meal {
            navigationItem.title = mealToEdit.name
            nameText.text = mealToEdit.name
            photoImg.image = mealToEdit.photo
            ratingControl.rating = mealToEdit.rating
        }
        
        setSaveButtonStatus()
    }
    
    //在定义meal对象时1,菜名不能为空，2,rating值范围(0-5)
    //因此当菜名文本框为空时禁用保存按钮，由于我们的自定义控件符合第二个条件因此无需考虑
    func setSaveButtonStatus() {
        let name = nameText.text ?? ""
        saveOutlet.isEnabled = !name.isEmpty
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    // MARK: UITextFieldDelegate
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        nameText.resignFirstResponder()
        return true
    }
    
    //进入编辑状态禁用save按钮
    func textFieldDidBeginEditing(_ textField: UITextField) {
        // Disable the Save button while editing.
        saveOutlet.isEnabled = false
    }

    //文本有效输入结束后启用save按钮
    func textFieldDidEndEditing(_ textField: UITextField) {
        setSaveButtonStatus()
        navigationItem.title = nameText.text
        
    }

    //MARK: 手势识别方法
    @IBAction func selectPhoto(_ sender: UITapGestureRecognizer) {
        let imagePickerController = UIImagePickerController()
        
        imagePickerController.sourceType = .photoLibrary
        
        imagePickerController.delegate = self
        
        present(imagePickerController, animated: true, completion: nil)
    }
    
    //图片选择之前取消事件
    func imagePickerControllerDidCancel(_ picker: UIImagePickerController){
        
        dismiss(animated: true, completion: nil)
    }
    
    //选中图片事件
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]){
        
        let selectedImage = info[UIImagePickerControllerOriginalImage] as! UIImage
        
        // Set photoImageView to display the selected image.
        photoImg.image = selectedImage
        
        // Dismiss the picker.
        dismiss(animated: true, completion: nil)
    }

    //取消按钮事件
    @IBAction func cancelBtn(_ sender: UIBarButtonItem) {
        
        //由于在修改和新增两种状态的取消回到第一个页面的方式不同，故需要分开处理
        //新增是通过导航控制器NavigationController来到此页面,故可作为条件
        let isPresentingInAddMealMode = presentingViewController is UINavigationController
        
        if isPresentingInAddMealMode {
            
            dismiss(animated: true, completion: nil)
        }
        else {
            navigationController!.popViewController(animated: true)
        }

    }
    
    //MARK: 保存数据
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if sender as! UIBarButtonItem === saveOutlet {
            let name = nameText.text ?? ""
            let photo = photoImg.image
            let rating = ratingControl.rating
            
            meal = Meal(name:name,photo:photo,rating:rating)
        }
    }

}