首先需要导入AVFoundation库。
UIImagePickerController
调用摄像头拍照，摄像的时候需要用到UIImagePickerController。
使用方法：
//实例化一个对象
UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;//设置照片源类型
imagePicker.mediaTypes = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];//设置媒体种类
imagePicker.allowsEditing = NO; //允许编辑
imagePicker.cameraFlashMode = UIImagePickerControllerCameraFlashModeAuto;//闪光灯模式
imagePicker.cameraDevice = UIImagePickerControllerCameraDeviceRear;//摄像头前置还是后置
imagePicker.delegate = self;//设置代理
//通过模态视图推出页面
[self presentViewController:imagePicker animated:YES completion:nil];
sourceType 的三种类型分别是：
UIImagePickerControllerSourceTypeCamera 照相机
UIImagePickerControllerSourceTypePhotoLibrary 照片库 (用户不可删除)
UIImagePickerControllerSourceTypeSavedPhotosAlbum 通过摄像头保存的照片（用户可删除）
如果需要对拍摄的照片或视频进行保存，需要给设置代理，然后遵守两个协议<UIImagePickerControllerDelegate,UINavigationControllerDelegate> ，实现下面的代理方法：
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info;
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker;
通常情况下，在didFinish方法里面对照片或视频进行保存处理；在didCancel方法里dismissViewController。
获取视频缩略图
这里我用的filePath是本地视频的存储路径；网络视频URL同理。
/**
* 获取视频的缩略图方法
*
* @param filePath 视频的本地路径
*
* @return 视频截图
*/
- (UIImage *)getScreenShotImageFromVideoPath:(NSString *)filePath{
UIImage *shotImage;
//视频路径URL
NSURL *fileURL = [NSURL fileURLWithPath:filePath];
AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:fileURL options:nil];
AVAssetImageGenerator *gen = [[AVAssetImageGenerator alloc] initWithAsset:asset];
gen.appliesPreferredTrackTransform = YES;
CMTime time = CMTimeMakeWithSeconds(0.0, 600);
NSError *error = nil;
CMTime actualTime;
CGImageRef image = [gen copyCGImageAtTime:time actualTime:&actualTime error:&error];
shotImage = [[UIImage alloc] initWithCGImage:image];
CGImageRelease(image);
return shotImage;
}
