781flyingdutchman
commented
1 year ago Hi, thanks for reaching out and great to hear the package meets your needs! If I understand it correctly, you want to download a list of files, and then check if all downloads succeeded. If you know the list of files you want to download, then I think the easiest way to do this is using downloadBatch: create a List of BackgroundDownloadTask objects, one for each file, in variable tasks, then download that list of files in a batch, like so:
FileDownloader.initialize(); // initialize only once
final result = await FileDownloader.downloadBatch(tasks);This method won't return until all tasks in the tasks list have been completed (either successfully, or failed). The return value (in result) is a DownloadBatch object that you can test - for example, you can use something like this:
if (result.numFailed > 0) {
print('${result.numFailed} tasks failed');
print(Failed tasks: '${result.failed.toList()}'); // in practice you would for example retry the .failed tasks
} else {
print('All tasks downloaded successfully');
}Alternatively, if you don't have the full list of tasks ready in advance, you can add each separately using enqueue, but you'll not have the convenience of the batch download - for example, you then need to listen to FileDownloader.updates to keep track of each task completion individually.
Either way, you may also want to manage what may happen when the app goes into the background/suspended, and then resumes. Status updates for tasks completed while in the background may not have been properly tracked by your app (this is a feature of the Android and iOS platforms, and is unavoidable), so when your app resumes you may want to check what tasks have completed or failed while the app was in the background.
There are many possible strategies here. A comprehensive one is to store your list of tasks in 'permanent' storage (e.g. in preferences, or in a simple database), so it survives app shutdowns and restarts. For convenience, you can call the .toJsonMap() method on a BackgroundDownloadTask to get a JSON representation that you can store as a String, and .fromJsonMap to create the object again.
Upon resume, you then check for existence of each file in that list, and if the file exists you remove the task from that list (because the download completed successfully while in the background, otherwise the file wouldn't be there). If your remaining list is empty, you are done. If not, you need to figure out if those remaining tasks are still running, or if they failed while in the background: query FileDownloader.allTaskIds to get a list of running download tasks, then iterate over that list and call Filedownloader.taskForId(taskId) to get the actual BackgroundDownloadTask object for each taskId, and compare that with your list of remaining downloads to make sure that all files you still need to download are indeed running. Those not running are the downloads that failed, and you can choose to enqueue those again, or handle failures differently.
A much simpler strategy is to store the timestamp of when you started your batch download in preferences, and upon resume IF not all files are downloaded AND substantial time has passed, THEN simply download the remaining files again. The right approach depends a lot on your application.
I hope this helps - let me know if you get it to work, and/or if you have suggestions to improve the package.
markst
Hi thanks for this awesome alternative package.🙏 I am thinking to switch from flutter downloader, as this package meets all of my requirements.
I have a question though which bits confuses me. Our app is complete offline app after file downloads and mostly used images and audio and very less video file.
In the app we have the list of task to be downloaded and hence it's exact length. I just want to Query if all the task has been downloaded (don't need progress for individual task) , but check for all file download completes.
So that later I can test the list of original download task and the completed Task have <= length of original list.l, that confirm that although some task failed but 90% of task are completed and I want to route to another page.
Thank-you and hope to get your response