Swift学习笔记（4）使用UIImagePickerController实现从设备图片库和照相机获取图片

设备图片库和照相机是图像的两个重要来源，使用UIKit中提供的图像选择器UIImagePickerController可以轻易地实现从设备图片库和照相机获取图片。

目录

声明协议

UIViewController需声明实现如下两个协议

class viewController: UIViewController , UIImagePickerControllerDelegate , UINavigationControllerDelegate{
...
}

创建UIImagePickerController

定义一个UIImagePickerController

var imagePicker:UIImagePickerController!

创建一个UIButton，在其IBAction中添加代码

设备图片库：

if self.imagePicker == nil{
    self.imagePicker = UIImagePickerController()
}
self.imagePicker.delegate = self
//设置图片来源为设备图片库
self.imagePicker.sourceType = .PhotoLibrary
self.presentViewController(self.imagePicker, animated: true, completion: nil)

照相机：

if UIImagePickerController.isSourceTypeAvailable(.Camera){
   if self.imagePicker == nil{
       self.imagePicker = UIImagePickerController()
   }
   self.imagePicker.delegate = self
   //设置图片来源为相机
   self.imagePicker.sourceType = .Camera
   self.presentViewController(self.imagePicker, animated: true, completion: nil)
}
 else{
  //弹出警告框
  let errorAlert = UIAlertController(title: "相机不可用", message: "", preferredStyle: UIAlertControllerStyle.Alert)
  let cancelAction = UIAlertAction(title: "确定", style: UIAlertActionStyle.Cancel, handler: nil)
  errorAlert.addAction(cancelAction)
  self.presentViewController(errorAlert, animated: true, completion: nil)
 }

UIImagePickerControllerDelegate委托

取消图片获取：

func imagePickerControllerDidCancel(picker: UIImagePickerController) {
     self.imagePicker = nil
     self.dismissViewControllerAnimated(true, completion: nil)
}

完成图片获取：

func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
     //从info中取出获取的原始图片
     let image = info[UIImagePickerControllerOriginalImage] as! UIImage    
     self.imageView.image = image
     //设置图片显示模式
     self.imageView.contentMode = .ScaleAspectFill
     self.imagePicker.delegate = nil
     self.dismissViewControllerAnimated(true, completion: nil)
}

UINavigationControllerDelegate协议

以下两个协议可以根据需求来选择是否实现

- navigationController:willShowViewController:animated
- navigationController:didShowViewController:animated

图片编辑

如果要将原始图片进行编辑如缩放，裁剪等后再使用

则在创建UIImagePickerController时添加：

self.imagePicker.allowsEditing = true

然后将实现UIImagePickerControllerDelegate中的

let image = info[UIImagePickerControllerOriginalImage] as! UIImage 

改为

let image = info[UIImagePickerControllerEditedImage] as! UIImage

iOS 9 中的新错误

如果在iOS 9 Xcode 7.1 以上的版本运行可能会报以下错误

_BSMachError: (os/kern) invalid capability (20)
_BSMachError: (os/kern) invalid name (15)

解决方法：

打开Info.plist，将Localization native development region中的值由en改为United States