最近有个需求:把屏幕内容录制下来保持到本地
这里ReplayKit不做介绍，想了解请看下面的链接
iOS端使用replaykit录制屏幕的技术细节
核心代码（最后附demo）
请求同意使用摄像头和麦克风权限，如果用户拒绝了，将无法进行录制。
不支持模拟器

{
    RPScreenRecorder *_recorder;
    NSURL *_movieUrl;
}

//    开始录制
  [_recorder startRecordingWithHandler:^(NSError * _Nullable error) {
        NSLog(@"视频录制开启产生问题=%@",error);
    }];

//    结束录制
    [_recorder stopRecordingWithHandler:^(RPPreviewViewController * _Nullable previewViewController, NSError * _Nullable error) {
        self->_movieUrl = [previewViewController valueForKey:@"movieURL"];
        [self export:[_movieUrl path] complete:^(ScreenRecError error, NSString *filePath) {
        [self writeVideoToAlbum:filePath];
    }];
    }];

//导出视频 mp4
- (void)export:(NSString *)filePathUrl complete:(void(^)(ScreenRecError error,NSString* filePath))complete {
    if (!filePathUrl) {
        NSLog(@"filePathUrl为空");
        return;
    }
    NSDate *date = [NSDate date];
    NSString *exportPath = [NSString stringWithFormat:@"%@%d.mp4",[self getCacheDir],(int)[date timeIntervalSince1970]*1000 ];
    NSURL *fileUrl = [NSURL fileURLWithPath:filePathUrl];
    AVAsset *fileAsset = [AVURLAsset assetWithURL:fileUrl];
    AVMutableComposition *mixComposition = [AVMutableComposition composition];
    if (!([fileAsset tracksWithMediaType:AVMediaTypeVideo].count>0 && [fileAsset tracksWithMediaType:AVMediaTypeAudio].count>0)) {
        complete(exportError,filePathUrl);
        return;
    }
    for (AVAssetTrack *track in fileAsset.tracks) {
        if ([track.mediaType isEqual:AVMediaTypeVideo]) {
            AVMutableCompositionTrack *compositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
            NSError *error;
            [compositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, fileAsset.duration) ofTrack:track atTime:kCMTimeZero error:&error];
        }
        else if([track.mediaType isEqual:AVMediaTypeAudio]){
            AVMutableCompositionTrack *compositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
            NSError *error;
            [compositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, fileAsset.duration) ofTrack:track atTime:kCMTimeZero error:&error];
        }
    }
    AVAssetExportSession *assetExport = [AVAssetExportSession exportSessionWithAsset:mixComposition presetName:AVAssetExportPreset1280x720];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    if ([fileManager fileExistsAtPath:exportPath]) {
        NSError *error = nil;
        [fileManager removeItemAtPath:exportPath error:&error];
        if (error) {
            NSLog(@"移除文件出错=%@",error);
        }
    }
    
    assetExport.outputFileType = AVFileTypeMPEG4;
    assetExport.outputURL = [NSURL fileURLWithPath:exportPath];
    assetExport.shouldOptimizeForNetworkUse = false;
    
    [assetExport exportAsynchronouslyWithCompletionHandler:^{
        if (assetExport.status == AVAssetExportSessionStatusCompleted) {
            NSLog(@"Record SaveTmpVideo Success");
            complete(nil,exportPath);
        }
        else {
            complete(exportError,filePathUrl);
        }
    }];
    
}

//保存图片到相册
- (void)writeVideoToAlbum:(NSString *)exportFilePath{
    
    UISaveVideoAtPathToSavedPhotosAlbum(exportFilePath, self, @selector(video:didFinishSavingWithError:contextInfo:), nil);
}

//保存视频完成之后的回调
- (void)video:(NSString *)videoPath didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo {
    if (error) {
        NSLog(@"保存视频失败%@", error.localizedDescription);
    }
    else {
        NSLog(@"保存视频成功"); 
    }
}

demo地址