The Android findViewById() method explained with examples

The findViewById() method is a method of Android’s View and Activity classes.

The method is used to find an existing view in your XML layout by its android:id attribute.

For example, suppose you have a TextView in your XML layout with the following definition:

<TextView
    android:id="@+id/id_text_view"
    android:text="Hello World!"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

You can get the TextView above in your Activity class with the following code:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    TextView myTextView = findViewById(R.id.id_text_view);
}

The same can be done for any valid Android View object, such as a Button or a CheckBox view.

When you call the findViewById() method, the method is usually called from the AppCompatActivity class, which is a subclass of the Activity class.

The findViewById() method accepts only one parameter, which is the id of the view with int type reference:

@Override
public <T extends View> T findViewById(@IdRes int id) {
    return getDelegate().findViewById(id);
}

The Android framework generates an internal reference of the id you specified in the XML layout. The internal reference is of an int type.

You need to refer to this generated int value by calling R.id in your code.

Using findViewById in Kotlin

In Kotlin, you can use the syntax to use the findViewById() method is as follows:

val myTextView = findViewById<TextView>(R.id.id_text_view)

You need to specify the generic type of the view inside the angle brackets <> as shown above.

And that’s how you use the findViewById() method when developing an Android project. 👍