How to Update UI from UI thread or Background thread. runonuithread() method in android. Threads in Android . How to update Ui from background Thread.

1] In the worker thread use the runonUithread() method and pass it a runnable.

YOU CANNOT ACESS runonuithread() method OUTSIDE THE ACTIVITY/MAIN ACTIVITY ,to acess outside the Activity , you need a  reference of the mainActivity.

    class Worker implements Runnable{

        @Override
        public void run() {
            int i=0;
           while (i< 10){
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                Log.d("MyTag","Started : " + Thread.currentThread().getName()+ " Counter at : " + i);
                i++;
            }
           //This part runs of the Main thread and makes changes to the Ui
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Log.d("Keyy",Thread.currentThread().getName());
                    TextView textView = findViewById(R.id.textview_display);
                    textView.setText(" Hello World ! ");
                }
            });
        }
    }
}

(A shortcut to run on new thread using Java Thread class)

public void setTextAfter5Sec(View view) {


    // Using JAVA Thread class for threading
    new Thread(new Runnable() {
        @Override
        public void run() {

            // Creating a new worker thread
            try {
                Thread.sleep(5000);
                Log.d(TAG, "setTextAfter5Sec : "+Thread.currentThread());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            // Using runOnUiThread since we worker thread cannot touch Ui directly.
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    textview.setText("5 seconds completed !");
                    Log.d(TAG, "setTextAfter5Sec : "+Thread.currentThread());
                }
            });

        }
    }).start();

}

useful video : https://youtu.be/Tzf-sPm5eTo