Android-Studio：如何从一个线程（另一个活动中的startet）更新聊天（ListView）

Question

Hey guys:) I'm currently working on an android project, where I want to realize a chat function. I know there are several tutorials which describe a chat app but I want to do it myself with my own Server. In my MainActivity I start a self written updater in a new thread (bc. of network-operations can only be done outside the UI thread), which permanently checks, if the chat-protocol, which is stored on my server (RaspberryPi), has new messages from other users. If there are new messages, the Updater downloads it and stores it in a string. This works fine! Now, when the updater receives a new message, I want to update the ListView in my Chat-Activity with the new message. This process should work at any time and update my ListView permanently (not with a refresh button or sth. like that). My question is: how do i realize this the smoothest way - a strategy, not necessarily code. One idea, which works but feels a bit random, is to write the received messages in a shared preferences-file and load it in the chat-acivity via an infinite loop in the chat activity. Is there a possibility to write the received messages directly in the ListView at any time from the thread with the updater which was startet in the MainActivity. If needed i could upload the current code but i want to do it directly and not with an infinite loop. Thanks for reading and maybe even for the help :)

Answer 1

You may want to save the received messages in SQLite database, and inside the activity, you can poll the database (suppose for every 5 seconds) and stop polling after the activity is destroyed.

Another way would be to use the static references of the views and update them from a different class. Even you are trying to update them from inside a background thread, you can update the UI using view.post()

SomeActivity.textView.post(new Runnable(){
    @Override
    public void run(){
       SomeActivity.textView.setText("sth");
    }
});