Load all fragments on app opening

call setOffscreenPageLimit with a number higher than half your fragments. This will force the viewpager to create and keep all of the fragments created as you have in your adapter.

@Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        viewPager = (ViewPager) findViewById(R.id.pager);
        // use a number higher than half your fragments.
        viewPager.setOffscreenPageLimit(4);
        FragmentManager fragmentManager=getSupportFragmentManager();
        viewPager.setAdapter(new MyAdapter(fragmentManager));     
}