Efeito Fade-in e Fade-out na transição de telas ou fragments

MainActivity.java

//Em Activity
Intent i = new Intent(MainActivity.this, Destino.java);
startActivity(i);
overridePendingTransition(R.anim.fadein, R.anim.fadeout);

// Em fragments (provavelmente já possúi um código parecido com este)
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.setCustomAnimations(R.anim.fadein, R.anim.fadeout); //animação aqui
transaction.commit();

res_anim_fadein.xml

<?xml version="1.0" encoding="utf-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
   android:interpolator="@android:anim/accelerate_interpolator"
   android:fromAlpha="0.0" android:toAlpha="1.0" android:duration="500" />

res_anim_fadeout.xml

<?xml version="1.0" encoding="utf-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
   android:interpolator="@android:anim/accelerate_interpolator"
   android:fromAlpha="1.0" android:toAlpha="0.0" android:duration="500" />