Progress bar for AVAssetExportSession

问题

I've got an app that exports an AVMutableComposition into a .mov file, and I'd like for the user to see the status of the export with a progress bar the same way that you would if you sent a text message or uploaded a file.

I know how to create a progress bar when I know the duration of a task (such as playing an audio file), but since there's no set duration for the export I'm unsure how to proceed.

I've got an activity indicator currently but it doesn't provide the best user experience.

Does anyone have any pointers?

回答1:

I came up with an answer a while back so I'll post it in case it can help someone:

First, in the method in which you call AVAssetExportSession you've got to set up a timer to update your UIProgressView once you've initiated the export:

//`AVAssetExportSession` code here
    self.exportProgressBarTimer = [NSTimer scheduledTimerWithTimeInterval:.1 target:self selector:@selector(updateExportDisplay) userInfo:nil repeats:YES];
...

Then you need a method to update your display taking into account that the progress property on AVAssetExportSession goes from 0 - 1:

- (void)updateExportDisplay {
    self.exportProgressBar.progress = exportSession.progress;
    if (self.exportProgressBar.progress > .99) {
        [self.exportProgressBarTimer invalidate];
    }
}

回答2:

Same issue i have faced in iOS 8.0, i resolved it using dispatch quee

- (void)convertVideoToLowQuailtyWithInputURL:(NSURL*)inputURL outputURL:(NSURL*)outputURL handler:(void (^)(AVAssetExportSession*))handler{

[[NSFileManager defaultManager] removeItemAtURL:outputURL error:nil];
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:inputURL options:nil];

exportSession2 = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetLowQuality];
exportSession2.outputURL = outputURL;
exportSession2.outputFileType = AVFileTypeQuickTimeMovie;

[exportSession2 exportAsynchronouslyWithCompletionHandler:^(void)
 {
     handler(exportSession2);
 }];

 dispatch_async(dispatch_get_main_queue(), ^(void){

      self.exportProgressBarTimer = [NSTimer scheduledTimerWithTimeInterval:.1 target:self selector:@selector(updateExportDisplay) userInfo:nil repeats:YES];
 });

}

回答3:

Swift 3 example

Using Notification Center to send progress updates to listeners

//`AVAssetExportSession` code above
var exportProgressBarTimer = Timer() // initialize timer
if #available(iOS 10.0, *) {
    exportProgressBarTimer = Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { timer in
    // Get Progress
    let progress = Float((exportSession?.progress)!);
    if (progress < 0.99) {
       let dict:[String: Float] = ["progress": progress]
       NotificationCenter.default.post(name: Notification.Name("ProgressBarPercentage"), object: nil, userInfo: dict)
    }
  }
}

// on exportSession completed
exportSession?.exportAsynchronously(completionHandler: {
   exportProgressBarTimer.invalidate(); // remove/invalidate timer
   if exportSession?.status == AVAssetExportSessionStatus.completed { 
      // [....Some Completion Code Here]
   }
})

Then setup the notification center listener anywhere you'd like using

NotificationCenter.default.addObserver(self, selector: #selector(self.statusUpdate(_:)), name: NSNotification.Name(rawValue: "ProgressBarPercentage"), object: nil)

回答4:

Use below lines of code.

AVAssetExportSession *session = [AVAssetExportSession exportSessionWithAsset:composition presetName:AVAssetExportPresetMediumQuality];
self.exportSession = session;

// 出力先（テンポラリファイル）の設定。
NSString *filePath = NSTemporaryDirectory();
filePath = [filePath stringByAppendingPathComponent:@"out.mov"];
[[NSFileManager defaultManager] removeItemAtPath:filePath error:nil];
session.outputURL = [NSURL fileURLWithPath:filePath];

// 出力タイプの設定。
session.outputFileType = AVFileTypeQuickTimeMovie;

// 非同期エクスポートの開始。
[session exportAsynchronouslyWithCompletionHandler:^{
    if (session.status == AVAssetExportSessionStatusCompleted) {
        // フォトアルバムへの書き込み。
        ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
        [library writeVideoAtPathToSavedPhotosAlbum:session.outputURL completionBlock:^(NSURL *assetURL, NSError *error){
            if (error) {
                self.resultLabel.text = [NSString stringWithFormat:@"アセット書き込み失敗\n%@", error];
            } else {
                self.resultLabel.text = [NSString stringWithFormat:@"完了\n%@", assetURL];
            }
        }];
        [library autorelease];
    } else if (session.status == AVAssetExportSessionStatusCancelled) {
        self.resultLabel.text = @"エクスポート中断";
    } else {
        self.resultLabel.text = [NSString stringWithFormat:@"エクスポート失敗\n%@", session.error];
    }
}];


dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
    while (session.status == AVAssetExportSessionStatusExporting) {
        dispatch_sync(dispatch_get_main_queue(), ^{
            self.progressView.progress = session.progress;
        });
    }
});

Reference Link : https://github.com/keijiro/iOS4BookSampleCode/blob/master/3.3.SimpleExport/Classes/SimpleExportViewController.m

来源：https://stackoverflow.com/questions/11090760/progress-bar-for-avassetexportsession

标签

iphone

cocoa-touch

uiprogressview

avassetexportsession