Android : textview resets every time i come back to the app

Im new in android development and I have to do an application that checks for the app running in foreground, and it should update a textview with the name of the apps. For the moment Im using a string, cause i cant reference a non final variable from the runnable inner class.

I have placed my code into a Runnable class into the oncreate method of my main activity, dont know if it is the right place to put it since I want to run that once, and then let the thread do his job with an infinite loop.

One of the several problems I found is when I run my application, every time i come back to the app, the textview is empty, then the thread begins to fill it with my string, but when i left the app and come back again, is empty.

How can i keep the contents of the textview?

I put my code here, thanks for the help.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if (!bExecuted)
    {
        bExecuted = true;

        setContentView(R.layout.activity_main);

        final TextView myText = (TextView) this.findViewById(R.id.my_view);
        final ActivityManager am = (ActivityManager) this.getSystemService(ACTIVITY_SERVICE);
        final PackageManager pm = this.getPackageManager();

        Runnable myRunnable = new Runnable() {
             @Override
             public void run() {

                 String foregroundTaskAppName = "";
                 String foregroundTaskAppNameOld = "";

                 while (true) 
                 {
                     try
                     {
                         Thread.sleep(500);
                        // The first in the list of RunningTasks is always the foreground task.
                        RunningTaskInfo foregroundTaskInfo = am.getRunningTasks(1).get(0);

                        String foregroundTaskPackageName = foregroundTaskInfo .topActivity.getPackageName();

                        PackageInfo foregroundAppPackageInfo;

                        foregroundAppPackageInfo = pm.getPackageInfo(foregroundTaskPackageName, 0);

                        foregroundTaskAppNameOld = foregroundTaskAppName;
                        foregroundTaskAppName = foregroundAppPackageInfo.applicationInfo.loadLabel(pm).toString();

                        if (!foregroundTaskAppNameOld.equals(foregroundTaskAppName))
                        {
                            myText.post(new Runnable() { 
                                @Override
                                public void run() {
                                    String textOld = (String)myText.getText();
                                    myText.setText(textOld + "hol\n");
                                }
                            });
                        }

                    } catch (NameNotFoundException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                  }
             }
        };

        Thread myThread = new Thread(myRunnable);
        myThread.start();
    }
}