I have a list of URI which contains multiple audio files. I am able to upload all the files to firebase storage and retrieve their URL successfully but the problem is that I want my app to wait until all files are uploaded and their URLs are retrieved and saved into a hashmap. My app is currently not waiting for the upload to finish. By doing some research, I found that I can use the async task to make my app wait until upload is finished. Now the problem is that i am not familier with asyn task and i don't know even a single thing about it. I don't know where to start. Can someone please help me to complete this task.