如何将 MVVM 与 asyncTask 或任何其他东西一起使用？

Question

我想使用 AsyncTaskLoader 但它已被弃用，所以我知道我可以使用 ViewModel 和实时数据或可变数据代替 AsyncTaskLoader，但我不知道如何将它们与异步任务一起使用。

Answer 1

First off, I would recommend using JobScheduler/WorkManager as Google states here .

However, if you are still interested in using AsyncTask/AsyncTaskLoader , something like this might help. Since ViewModel holds a reference to a LiveData and the ViewModel updates the View (Activity or Fragment) , you can make a background network call(using AsyncTaskLoader) and update the liveData when onLoadFinished is called. This update of LiveData should trigger the observable and eventually the View ( Activity/Fragment )

Note: Make sure that the data you get back from the API call (For eg: <POJO.class> ) is of type MutableLiveData / LiveData .

Answer 2

LiveData with ViewModel is still latest, and you can use simple AsyncTask with Android Architecture Components (LiveData and ViewModel) in order to make AsyncTask lifecycle aware. Loader is not as efficient as this method of doing background task. Since you already know how to write AsyncTask, you only need it wrapped with LiveData and ViewModel: it works like a magic. For information on using AsyncTask with LiveData and ViewModel, you can look it up at https://medium.com/androiddevelopers/lifecycle-aware-data-loading-with-android-architecture-components-f95484159de4

Answer 3

Using AsyncTask with ViewModel defeats the purpose of using ViewModel.

ViewModel basic use case is:

public class MyViewModel extends ViewModel {
    private MutableLiveData<List<User>> users;
    public LiveData<List<User>> getUsers() {
        if (users == null) {
            users = new MutableLiveData<List<User>>();
            loadUsers();
        }
        return users;
    }

    private void loadUsers() {
        // Do an asynchronous operation to fetch users.
    }
}

In the loadUsers you are suppose to do the job - in background thread. You could use AsyncTask here but it makes no sense as you would not benefit from its doInBackground() and onPostExecute() methods.