问题
I am trying to chain a few AsyncTask classes inside a single Activity, which will then show another Activity once they are all completed (successfully). Currently I am chaining them off each others' onPostExecute() method but I do not like this because it somewhat couples the implementations unnecessarily.
For example, I have my ImportVideoActivity which the users enters a YouTube URL to be downloaded. To do so, I have two AsyncTask classes:
YouTubeVideoInfoTask: Gets the video metadata info as well as enumerating through available video formats (quality and codecs).YouTubeVideoDownloadTask: Performs the video download given a URL from the video info metadata.
I want the ImportVideoActivity to first execute a YouTubeVideoInfoTask to enumerate the video qualities and pick the best one. After that, it should execute a YouTubeVideoDownloadTask and upon completion start the CropVideoActivity with the downloaded video.
How can I chain these two AsyncTask classes elegantly inside of the ImportVideoActivity? Is there some kind of listener/callback that allows me to monitor when these tasks complete and start the next one without using the AsyncTask.onPostExecute() method?
回答1:
Yes. Use a Callback Listener in your Activity. As soon as this is called, you can start the new AsyncTask from your Activity.
Example in my other answer: How to return an object from the asynctask to the main class in android
来源：https://stackoverflow.com/questions/24194651/asynctask-chaining-in-activity-callback