前言

照片的选取在App中是相当普遍的场景，如用户修改头像、上传照片。一般给用户两种选择

1拍照
2从相册选取

在iOS中选择图片这个任务是通过UIImagePickerController来实现的，通过设置sourceType来决定是从相册选取还是拍照，当前的视图控制器需要实现UIImagePickerControllerDelegate协议的方法。

imagePickerController:didFinishPickingMediaWithInfo:
//用户选择了图片
imagePickerControllerDidCancel:
//用户取消选择

由于iOS系统的隐私保护机制，无论那种方式都必须先由用户授权否则我们没有权限，结果如下图

没有权限

1，我们希望这个体验进行优化，2，这个场景很多，我们希望将其模块化,以便复用和拆封ViewController。我们这里只讨论选择一张图片的情况，多选照片的类库代码，现成类库比较多。

实现

综合来说我们的流程如下：1.弹出视图供用户选择一种方式；2.确定App是否有相应的权限，如果没有，提示用户没有权限并尝试引导用户去设置里面进行授权；3.选择照片返回。注意:UIActionSheet和UIAlertView在iOS9中已经废弃，提倡使用UIAlertController。考虑后期的复用、维护与完善，我们将其进行封装先定义一个ImagePickerModelDelegate协议，用来和视图控制器进行交互。

@protocol ImagePickerModelDelegate
-(void)imagePickerDidFinishWithImage:(UIImage)image;
-(void)imagePickerDidCancel;
//弹出警告框的视图
-(UIView)viewControllerView;
@end

新建NSObject的子类ImagePickerModel，并实现UIImagePickerControllerDelegate和UIActionSheetDelegate协议。声明两个方法

+(id)sharedInstance;
-(void)startShowSelectTypeViewWithViewController:(id)viewController andIsEdit:(BOOL)edit;

.m文件方法的实现

+(id)sharedInstance
{
    if (!model)
   {     
       model = [[ImagePickerModel alloc]init];  
       if([[UIDevice currentDevice]systemVersion]floatValue] >= 8.0)
      {
          isiOS8 = YES;
      } 
   }
    return model;
}
-(void)startShowSelectTypeViewWithViewController:(id)viewController andIsEdit:(BOOL)edit
{
     isEdit = edit;
    _delegate = viewController;
    UIActionSheet *actSheet = [[UIActionSheet alloc]initWithTitle:nil delegate:self cancelButtonTitle:@"取消" destructiveButtonTitle:nil otherButtonTitles:@"相册",@"拍照", nil];
       [actSheet showInView:[_delegate viewControllerView]];
       [self takePicFromAlbum];
}
-(void)actionSheet:(UIActionSheet *)actionSheet
clickedButtonAtIndex:(NSInteger)buttonIndex
{
     switch (buttonIndex)
     {
          case 0:
          {
               [self takePicFromAlbum];
               break;
          }
          case 1:
          {
               [self takePicFromCamera];
               break;
          }
          default:
          break;
     }
}```

无论那种操作之前，都先判断下权限

//从相册选取

• (void)takePicFromAlbum
  {
  ALAuthorizationStatus author = [ALAssetsLibrary authorizationStatus];
  if (author == 1 || author == 2)
  {
  if(isiOS8)
  {
  UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:@"警告" message:@"没有相册访问权限，请在设置-隐私-相册中进行设置！" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"设置",nil];
  }
  else
  {
  UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:@"警告" message:@"没有相册访问权限，请在设置-隐私-相册中进行设置！" delegate:nil cancelButtonTitle:@"取消" otherButtonTitles:nil];
  }
  [alertView show];
  return;
  }
  UIImagePickerController pick = [[UIImagePickerController alloc] init];
  pick.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
  pick.delegate = self;
  pick.allowsEditing = isEdit;
  [(UIViewController)_delegate presentViewController:pick animated:YES completion:nil];
  }
  //从相机
• (void)takePicFromCamera
  {
  AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
  if (authStatus == AVAuthorizationStatusRestricted || authStatus ==AVAuthorizationStatusDenied)
  {
  if(isiOS8)
  {
  UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:@"警告" message:@"没有相机访问权限，请在设置-隐私-相机中进行设置！" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"设置",nil];
  }
  else
  {
  UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:@"警告" message:@"没有相机访问权限，请在设置-隐私-相机中进行设置！" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"设置",nil];
  }
  [alertView show];
  return;
  //无权限
  }
  if ([UIImagePickerController
  isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera])
  {
  UIImagePickerController pick = [[UIImagePickerController alloc] init];
  pick.sourceType = UIImagePickerControllerSourceTypeCamera;
  pick.delegate = self;
  pick.allowsEditing = isEdit;
  [(UIViewController)_delegate presentViewController:pick animated:YES completion:nil];
  }
  else
  {
  NSLog(@"没有相机权限！");
  }
  }

-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
//iOS8后允许打开系统设置
if (buttonIndex == 1)
{
[[UIApplication sharedApplication]openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
}
}

选择或者取消后的操作

pragma mark - UIImagePickerController

• (void)imagePickerController:(UIImagePickerController *)picker
  didFinishPickingMediaWithInfo:(NSDictionary *)info
  {
  UIImage *image = [info objectForKey:UIImagePickerControllerEditedImage];
  if (!image)
  {
  image = [info objectForKey:UIImagePickerControllerOriginalImage];
  }
  [_delegate imagePickerDidFinishWithImage:image];
  picker.delegate = nil;
  [picker dismissViewControllerAnimated:YES completion:nil];
  }
  -(void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
  {
  picker.delegate = nil;
  [picker dismissViewControllerAnimated:YES completion:nil];
  [_delegate imagePickerDidCancel];
  }