findViewById() returns null when I call it in onCreate()

Question

I'm having a problem with the findViewById on my first android app. I'm trying to call this function but always return null. My app have 2 activities. In the second activity (activity_display_message) I have this code: ``` @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_display_message); if (savedInstanceState == null) { getSupportFragmentManager().beginTransaction() .add(R.id.container, new PlaceholderFragment()) .commit(); } //Obtener el mensaje desde el intent en MainActivity Intent intent = getIntent(); String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE); //Buscar el textview en la vista TextView textView = (TextView) findViewById(R.id.texto); textView.setText(message); } ``` And this is the fragment_display_message.xml ``` <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" andr…

Accepted Answer

`Activity` `findViewById()` searches the activity's view hierarchy set with `setContentView()` for the given view id. The view you appear to be looking for is in a fragment and not in the activity hierarchy (yet). Fragment transactions are not immediate either so even if you add it to the container in the activity hierarchy, it is not attached there right away but only when the transaction is processed.

In theory it's possible to synchronously execute pending fragment transactions with `executePendingTransactions()`. However, it's better to just move the code that touches a fragment's views in its `onCreateView()`. Fragments and their hosting activities are supposed to be relatively independent of each other, so an activity accessing a fragment's internals should be avoided.

findViewById() returns null when I call it in onCreate()

Solution

Problem