Proper way to implement Android XML onClick attribute in Activity

Question

I have used the android:onClick attribute extensively in my XML layouts for my Android application.

Example:

<Button
    android:id="@+id/exampleButton"
    android:onClick="onButtonClick" />

Is it proper to create an Interface to enforce the implementation of those onClick methods in Activities that use that layout file?

public interface MyButtonInterface {
    public onButtonClick(View v);
}

Answer 1

Why do you want an interface? Is it to enforce at compile time that the activity class has the methods that are defined in the onClick attributes in the XML?

Personally I wouldn't bother.

• Who enforces the interface has the right methods?
• Who enforces the right interface is used on each activity?

Just accept that due to the flexible nature of the interaction between Android activities & layouts, it's not possible to enforce at compile time that the onClick function actually exists. As far as I know, anyway. Anyone prove me wrong?

Answer 2

<?xml version="1.0" encoding="utf-8"?> 
<!-- layout elements -->
<Button android:id="@+id/mybutton"
    android:layout_width="wrap_content"  
    android:layout_height="wrap_content"  
    android:text="Click me!"  
    android:onClick="myFancyMethod" />  
<!-- even more layout elements -->

The above code just shows the XML implementation. Now in the background Android does nothing else than the Java code calling your method on a click event.

Note that with the XML above, Android will look for the onClick method myFancyMethod() only in the currently active Activity's .java file. This is important to remember if you are using fragments, since even if you add the XML above using a fragment, Android will not look for the onClick method in the .java file of the fragment used to add the XML.

protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.dialog);
}

public void myFancyMethod(final View view) {
    System.out.println("clicked");
}