Alex Mercer Alex Mercer - 4 months ago 27
Android Question

Start ObjectAnimator after fragment transaction

i have this method to scroll my textview from left to right:

public void scrollText() {
float startX = 0 - scrollTxt.getWidth();
float endX = scrollTxt.getWidth();
ObjectAnimator anim = ObjectAnimator.ofFloat(scrollTxt, View.X, startX, endX);
anim.setRepeatCount(ValueAnimator.INFINITE);
anim.setRepeatMode(ValueAnimator.RESTART);
anim.setDuration(9000);
anim.start();
}


this method and the textview are in a fragment. i add this fragment in my activity with this code:

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

drawer = (DrawerLayout) findViewById(R.id.activity_main_drawer);

MainFragment mainFragment = new MainFragment();
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.add(R.id.activity_main_frame, mainFragment);
ft.commit();

NavigationView navigationView = (NavigationView) findViewById(R.id.activity_main_nav);
navigationView.setNavigationItemSelectedListener(new MainNavigationListener(drawer));
}


i want to start animation when fragmnet added.
i put scrollText() method in fragmnet's onResume but it didn't work.

Answer

This happens because scrollTxt.getWidth()is zero in onResume() because your fragment view hierarchy hasn't been measured yet. As a solution, you can postpone the animation start to the next layout pass by calling scrollTxt.post().

Try this:

@Override
public void onResume() {
    super.onResume();
    scrollTxt.post(new Runnable() {
        @Override public void run() {
            scrollText();
        }
    });
}
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