Android Question Minimizes app and open again to show all views

I have a doubt in B4XPages. I have a screen named "Lab Billing". When the user enters this screen, some views are not visible until the user clicks the retrieve button. but the problem is, once all views are visible after clicking the retrieve button, the user minimizes the app and again opens the app, the some views that become visible after retrieved are not visible. I have written some codes in B4XPage_Appear which is why I have this error. How would you like to overcome this? I have attached my project.