小编Pet*_*ter的帖子

我用AVFoundation创建了一个类似于Snapchat的自定义相机.图片方面有效:拍照并显示图片.现在我正在尝试拍摄视频并显示视频.

我已经捕获了一个成功的视频文件,经过测试并与MPMoviePlayer配合使用,但无法在AVPlayer上播放.

- (void)takeVideoAction:(id)sender {
    NSString *outputPath = [NSTemporaryDirectory() stringByAppendingPathComponent:@"output.mp4"];

    NSFileManager *manager = [[NSFileManager alloc] init];
    if ([manager fileExistsAtPath:outputPath]){
        [manager removeItemAtPath:outputPath error:nil];
    }
   [movieFileOutput startRecordingToOutputFileURL:[NSURL fileURLWithPath:outputPath] recordingDelegate:self];
}

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray *)connections error:(NSError *)error{


            AVURLAsset *asset = [AVURLAsset URLAssetWithURL:outputFileURL options:nil];
            [asset loadValuesAsynchronouslyForKeys:@[@"tracks"] completionHandler:^{
            dispatch_async(dispatch_get_main_queue(), ^{
                 NSError *error = nil;
                 if([asset statusOfValueForKey:@"tracks" error:&error] == AVKeyValueStatusFailed){
                    NSLog(@"error: %@", [error description]);
                }
                else{
                    self.playerItem = [AVPlayerItem playerItemWithAsset:asset];
                    self.player = [AVPlayer playerWithPlayerItem:self.playerItem];
                    self.playerLayer = [AVPlayerLayer playerLayerWithPlayer:self.player];
                    self.playerLayer.frame = self.view.bounds;
                    [self.view.layer addSublayer:self.playerLayer]; …

我需要知道何时AVPlayer完全加载了视频资产,因此没有视频延迟/冻结.当我开始播放视频时,它播放一半然后冻结.如果我退出并再次打开,它将播放视频的其余部分,并将平滑地重复播放视频.首先我加载资产:

AVURLAsset *asset = [AVURLAsset URLAssetWithURL:url options:nil];
NSString *tracksKey = @"tracks";

[asset loadValuesAsynchronouslyForKeys:@[tracksKey] completionHandler:
 ^{

     // Completion handler block.
     dispatch_async(dispatch_get_main_queue(),
                    ^{
                        NSError *error;
                        AVKeyValueStatus status = [asset statusOfValueForKey:tracksKey error:&error];

                        if (status == AVKeyValueStatusLoaded) {
                               AVPlayerItem *item = [AVPlayerItem playerItemWithAsset:asset];
                               // Set Key-Observers
                        }
                      });
       }];

我在项目上设置了三个关键观察者,并为玩家设置项目

 [item addObserver:self forKeyPath:@"status"
                                      options:NSKeyValueObservingOptionNew context:&ItemStatusContext];

[item addObserver:self forKeyPath:@"playbackLikelyToKeepUp"
                                      options:NSKeyValueObservingOptionNew context:&playbackLikelyToKeepUp];

[item addObserver:self forKeyPath:@"playbackBufferFull"
                                      options:NSKeyValueObservingOptionNew context:&playbackBufferFull];

 self.player = [AVPlayer playerWithPlayerItem:item];

接下来,我检查播放器/项目是否准备好播放,以及playBackLikelyToKeepUp是否为真.

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

   if ((context == …

我有一个UICollectionView我正在加载多个图像.从我读过的内容来看,为了将正确的图像与每个单元格匹配,我需要子类化UIImageView并在那里获得图像.因为每次我collectionView reloadData,一些图像重复,它们都是乱序.但我不确定如何做到这一点,并没有找到任何教程.我正在使用Parse作为数据库.

 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
albumImageCell *cell = (albumImageCell *) [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

     if (cell == nil) {
         cell = [[albumImageCell alloc]init];
     }

     PFObject *temp = [_dataArray objectAtIndex:indexPath.row];
     PFFile *file = [temp objectForKey:@"imageThumbnail"];

     if (![cell.hasImage isEqualToString:@"YES"]) {
         dispatch_async(imageQueue, ^{
             NSData *data = [file getData];
                 if (data) {
                     UIImage *image = [UIImage imageWithData:data];

                     dispatch_async(dispatch_get_main_queue(), ^(void){
                         cell.imageView.image = image;
                         cell.hasImage = @"YES";
                     });

                 }
         });
     }

     return cell;
}

我有两个collectionViews.一个collectionViewController和标题中的另一个collectionView.当我向下滚动collectionViewController时,标题collectionView的collectionView单元格消失.标头中还有一个segControl,用于更改collectionViewController单元格,这也使标题collectionView单元格消失.当控制器出现所有单元格都存在时,但是当我滚动选择segControl时,标题集合视图单元格消失.collectionViewController工作正常,只是标题中的那个搞砸了.

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return 1;
}


- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
if (collectionView == self.collectionView) {
    return [self.dataArray count];
}
return [self.groupArray count];
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

if (collectionView != self.collectionView) {
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"socialCell" forIndexPath:indexPath];
    PFObject *group = [self.groupArray objectAtIndex:indexPath.row];
    UILabel *label = (UILabel *) [cell viewWithTag:55];
    label.text = [group objectForKey:@"Title"];
    return cell;
}

    userPostCell *postCell = (userPostCell *) [collectionView dequeueReusableCellWithReuseIdentifier:@"postCell" forIndexPath:indexPath];
    userPictureCell *pictureCell = (userPictureCell *) [collectionView dequeueReusableCellWithReuseIdentifier:@"pictureCell" forIndexPath:indexPath];
    userEventCell …