How do I make a android AsyncTask loading spinner while doInBackgroung()

Question

I got an AsyncTask for URL connection. Now I want to have a loading spinner everytime I do the URL connection. I display the loading spinner in onPreExecute() and dismiss it in onPostExecute. I tested this with an endless while loop in doInBackgroung(). The big problem is the GUI is freezing and the loading spinner is not shown. In my opinion the reason is URLconnection.execute().get(). But I need the get() because the activity need the result to working with it.

My question is now: What is the best way to do this to achieve my wishes? (By the way it is not important to get a solution with an "AsyncTask solution" because there are maybe better solutions and AsyncTask will be deprecated with SDK version 30)

Thank you very much and stay healthy!

score 0 · Answer 1 · answered Aug 27 '20 at 18:11

As you said AsyncTask will be deprecated. So it is better to go for an alternative.

Since you mentioned you are not relying on AsyncTask, I will present to you another approach.

Let me introduce you to coroutines and convince you that they will solve your problem and "get the job done".

When I got to know about coroutines, this video was one of the first example that has demonstrated to me the potential of using coroutines in my app. At that point I was still using 100% Java, probably like you are right now.

The good part is: getting started with Kotlin is really easy! Not only you can call Kotlin functions from Java Code, you can also call Java functions from Kotlin code.

To "do something in background" in Kotlin, all you need to do is to launch a coroutine (on a background thread). Do you have a ViewModel to fetch your data? If it is an option to transfer this file to kotlin, then starting (and scoping) a coroutine becomes as simple as this. For fragments or activitities you could use other copes as well. However, using the global scope is usually discouraged.

Executing coroutines is as simple as that:

class MyViewModel: ViewModel() {
    fun loadDataInBackgroundAndShowSpinner {
        viewModelScope.launch {
            // Coroutine that will be canceled when the ViewModel is cleared.

           // start your spinning

           // do all the heave data work on a background thread
           doInBackground()

          // end your spinning here
        }
    }

    suspend fun doInBackground(inputURL: String) {
        withContext(Dispatchers.IO) {
            // Execute all your data fetching here
            ...
            // Assign your data to your viewModel variables, post it to a LiveData object, etc.
        }
    }
}

You do not need any loops in the main thread or anything. By using withContext on a background thread you can achieve main-safety. Within a launched coroutine, everything (by default) gets executed in order. Still you will not block the Main Thread. How did you achieve that? The key here is that your doInBackground function has the suspend keyword. Therefore your loadDataInBackgroundAndShowSpinner on the main thread will "suspend" your doInBackground function and the main thread is able to do whatever you want (i.e. nothing freezes). Then, once your doInBackground is finished, it will resume execution and you can just dismiss your spinner again on the main thread.

Kotlin coroutines make it so much easier to do something in the background and I really want to encourage you to give it a try! It will definitely solve your problem and I can not think of a more easy way. Google also tried to make it as easy as possible to get you started when coming from Java.

How do I make a android AsyncTask loading spinner while doInBackgroung()

1 Answers1