How to make a periodic code run off the UI thread in Android

Question

The following code is what I'm using currently, but there is an issue that the Toast is being shown, so it probably is in the UI thread isn't it? I do not want the run() function to run on the UI thread as I will probably add some heavy downloading there. However, I want to repeatedly execute this code (after every 9000ms) So what must I do, to either make this run off the UI thread, or a solution to my problem. Thank you.

    final Handler handler = new Handler();
    Thread feedthread = new Thread()
    {
        @Override
        public void run() {
            super.run();
            Toast.makeText(context, "UI", Toast.LENGTH_SHORT).show();
            handler.postDelayed(this, 9000);
        }
    };
    handler.postDelayed(feedthread, 9000);

Please do not suggest AsyncTask to me unless there is a way to repeat the code without using a while loop wasting resources or setting the thread to sleep. I would like answers to what I asked, and I do not want to run the code on the UI thread.

You can use AsyncTask instead of Thread, it has callbacks for this UI stuff. — ElDuderino, Dec 05 '15 at 18:07
I want to run the runnable at a later time, and I want it to run asynchronously, hence I delayed the post of a new thread. If this is the wrong way, please help me on which is right. I would prefer not to use async tasks or setting the thread to sleep — A B, Dec 07 '15 at 05:35

score 0 · Answer 1 · answered Dec 05 '15 at 18:03

You need to call the runOnUiThread method to show the Toast

final Handler handler = new Handler();
Thread feedthread = new Thread()
{
    @Override
    public void run() {
        super.run();
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                Toast.makeText(context, "UI", Toast.LENGTH_SHORT).show();
            }
        });
        handler.postDelayed(this, 9000);
    }
};
handler.postDelayed(feedthread, 9000);

I DON'T want to show the toast, I don't want the code to run on the UI thread, and the toast was just to check if it does. — A B, Dec 05 '15 at 18:10

mikejonesguy · Answer 2 · 2015-12-05T18:21:03.340

You want to use the AsyncTask class. Here is an example to show how it works:

// Async Task Class
private class MyTask extends AsyncTask<String, String, String> {

    // (Optional) Runs on the UI thread before the background task starts
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // Do some UI stuff if needed
    }

    // Runs on a background thread
    @Override
    protected String doInBackground(String... param) {
        String url = param[0];
        // Do something with the param, like kick off a download
        // You can also use publishProgress() here if desired at regular intervals
        /*while (isDownloading) {
            publishProgress("" + progress);
        }*/
        return null;
    }

    // (Optional) Runs on the UI thread periodically during the background task via publishProgress()
    protected void onProgressUpdate(String... progress) {
        // Update UI to show progress
        /* prgDialog.setProgress(Integer.parseInt(progress[0])); */
    }

    // (Optional) Runs on the UI thread after the background task completes
    @Override
    protected void onPostExecute(String file_url) {
        // Do some UI stuff to show completion of the task (if needed)
    }
}

You can run your task like this:

String url = getInternetUrl();
new MyTask().execute(url);

score 0 · Answer 3 · edited May 23 '17 at 12:23

Java Thread

new Thread(new Runnable(){
    private boolean stopped = false;

    @Override
    public void run(){
        while(!stopped) {    
            // Do, do, do...
            try {
                Thread.Sleep(9000);
            } catch(Exception e){}
        }
    }
}).start();

Android Handler

Also you can use Android handler class to run a code periodically. This requires you to have a looper-prepared thread to attach the handler to. Basically, a looper-prepared thread is assign a queue and every message posted to this thread will be queued and processed one by one in a queue manner.

This approach has a difference with the former one and is that if your do a lot of work in that background thread so that takes some time, then subsequent queued messages will be processed quicker than the interval (in this case, 9 seconds). Because looper-enabled threads immediately process the next queued message, once they are done with the previous one.

Find More Info Here

Note: You shouldn't [and can't] use this approach as an alternative to Service. This newly created thread does need an underlying component (either Activity or Service) to keep it alive.

All I was advised is, to not use Thread.sleep and instead use postdelayed as thread sleep keeps the resources alive until it wakes up again, I don't know properly. But if there is a disadvantage to thread.sleep, please could you edit the code to have delayed post by a handler? — A B, Dec 07 '15 at 05:34

How to make a periodic code run off the UI thread in Android

3 Answers3

Java Thread

Android Handler