一.从相册里面选择图片到App中

1.选择单张

    1>.UIImagePickerController(自带选择界面的)
    2>.AssetsLibrary(选择界面需要开发者自己搭建)
    3>.Photos(选择界面需要开发者自己搭建)

2.多张图片选择(图片数量>2)

    1>.AssetsLibrary
    2>.Photos

二.利用相机拍一张照片到APP

   1>.UIImagePickerController
   2>.AVcaptureSeccion.可以定义拍照界面样式

选择单张照片

/// 选择照片
- (IBAction)selectPhoto:(UIButton *)sender {
    UIAlertController *alterConroller = [UIAlertController alertControllerWithTitle:@"请选择方式" message:nil preferredStyle:UIAlertControllerStyleActionSheet];
    UIAlertAction *cameraAction = [UIAlertAction actionWithTitle:@"照相机" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        [self openCamera];
    }];
    UIAlertAction *albumAction = [UIAlertAction actionWithTitle:@"相册" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        [self openAlbum];
    }];
    [alterConroller addAction:albumAction];
    [alterConroller addAction:cameraAction];
    [self presentViewController:alterConroller animated:YES completion:nil];
}
/// 打开照相机
- (void)openCamera{
    //UIImagePickerControllerSourceTypePhotoLibrary, 从所有相册选择
    //UIImagePickerControllerSourceTypeCamera, //拍一张照片
    //UIImagePickerControllerSourceTypeSavedPhotosAlbum//从moments选择一张照片
    //判断照相机能否使用
    if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) return;
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.sourceType = UIImagePickerControllerSourceTypeCamera;
    picker.delegate = self;
    [self presentViewController:picker animated:YES completion:nil];
}
/// 打开相册
- (void)openAlbum{
    //UIImagePickerControllerSourceTypePhotoLibrary, 从所有相册选择
    //UIImagePickerControllerSourceTypeCamera, //拍一张照片
    //UIImagePickerControllerSourceTypeSavedPhotosAlbum//从moments选择一张照片
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
    picker.delegate = self;
    [self presentViewController:picker animated:YES completion:nil];
}
#pragma mark - ******UIImagePickerControllerDelegate******
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info{
    [picker dismissViewControllerAnimated:YES completion:nil];
    self.imageView.image = info[UIImagePickerControllerOriginalImage];
    NSLog(@"%@",info);
}

• 注意事项

UIImagePickerController的代理有2个遵循2个代理<UINavigationControllerDelegate, UIImagePickerControllerDelegate>