Injecting Views - PerfectCarl/androidannotations GitHub Wiki

Since AndroidAnnotations 1.0

@ViewById

The @ViewById annotation indicates that an activity field should be bound with the corresponding View component from the layout. It is the same as calling the findViewById() method. The view id can be set in the annotation parameter, ie @ViewById(R.id.myTextView). If the view id is not set, the name of the field will be used. The field must not be private.

Usage example:

@EActivity
public class MyActivity extends Activity {

  // Injects R.id.myEditText
  @ViewById
  EditText myEditText;

  @ViewById(R.id.myTextView)
  TextView textView;
}

@AfterViews

The @AfterViews annotation indicates that a method should be called after the views binding has happened.

When onCreate() is called, @ViewById fields are not set yet. Therefore, you can use @AfterViews on methods to write code that depends on views.

Usage example:

@EActivity(R.layout.main)
public class MyActivity extends Activity {

    @ViewById
    TextView myTextView;

    @AfterViews
    void updateTextWithDate() {
        myTextView.setText("Date: " + new Date());
    }
[...]

You can annotate multiple methods with @AfterViews. Don't forget that you should not use any view field in onCreate():

@EActivity(R.layout.main)
public class MyActivity extends Activity {

    @ViewById
    TextView myTextView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // DON'T DO THIS !! It will throw a NullPointerException, myTextView is not set yet.
        // myTextView.setText("Date: " + new Date());
    }
[...]

Recall that injection is always made as soon as possible. Therefore, it's safe to use any field annotated, e.g., with @Extra or @InstanceState in @AfterViews methods as these tags don't require any view to be set (as @AfterViews do). Therefore you can safely assume that such fields will be already initialized with their intended values in methods annotated with @AfterViews:

@EActivity(R.layout.main)
public class MyActivity extends Activity {

    @ViewById
    TextView myTextView;

    @InstanceState
    Integer textPosition;

    @AfterViews
    void updateTextPosition() {
        myTextView.setSelection(textPosition); //Sets the cursor position of myTextView
    }
[...] // The remaining code must keep textPosition updated.