CODEWITHSUNDEEP
javaandroidinheritancebuttonlistener
Piero
Piero

Reputation: 199

add functionality to an onClickListener in a derived class

I've read many threads on how to create and handle Button clicks using onClickListener. However, I couldn't find anything that solved this problem.

I have a class myActivity and I would like to create a second class myExtendedActivity which extends myActivity by adding some extra functionality. The class myActivity contains a lot of code which, for maintainability reasons, I don't want to duplicate. myExtendedActivity should behave exactly as myActivity with some extra function.

In particular in the onCreate method in myActivity I have the following code that add an onClickListener to my_button. The extended activity should just append a call to myExtraMethod.

myButton = (Button)findViewById(R.id.my_button); 
myButton.setOnClickListener(new View.OnClickListener() 
{
    public void onClick(View v) 
    {
        [...]   //a lot of code here

        myExtraMethod();

    }
});

Note that myExtraMethod simply broadcasts an Intent and it is not affected by any other part of the code in the Listener.

What I would like to do is to extend the OnClickListener in myExtendedActivity so that it first executes exactly the code written for myActivity and than myExtraMethod defined in myExtendedActivity.

I don't want to modify myActivity which should be completely unaware if myExtendedActivity is included in the project or not.

Thank you very much

Upvotes: 0

Views: 985

Answers (3)

deekay
deekay

Reputation: 681

Completely without modifying myActivity is barely possible.

You could use something like this in MyActivity (Some variant of the Template method pattern):

onCreate() {
    myButton.setOnClickListener(new View.OnClickListener() 
    {
        public void onClick(View v) 
        {
           myMethod();
        }
    });

}

protected void myMethod() {
    [...]   //a lot of code here
}

And then in MyExtendedActivty:

@Override
protected void myMethod() {
    super.myMethod();
    myExtraMethod();
}

Upvotes: 2

Alex DiCarlo
Alex DiCarlo

Reputation: 4891

Without modifying myActivity, you can't because you're instantiating an anonymous class, and the subclass has no way to "hook in" to that anonymous class.

If you can modify myActivity, then you could make the anonymous class from myButton.setOnClickListener(...) a static class, and in your subclass extend the listener class calling super.onClick(v), followed by the functionality you expect.

Then add a method to get the correct listener 

myButton.setOnClickListener(createMyButtonsListener())

that you can then override in the subclass providing the extended version.

Alternatively, add a method that can be overriden in a subclass (i.e. myExtraMethod()). that is called within your anonymous class.

Upvotes: 0

agamov
agamov

Reputation: 4427

If I understood your question right, the solution might be something like this:

In your layout for button you define the onClickListener from xml:

<Button
        android:id="@+id/myButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="handleButtonClick"
    />

Then, in MyActivity you implement method:

public void handleClick(View view) {

}

And in MyExtendedActivity you override it:

public class MyExtendedActivity extends MyActivity {
    @Override
    public void handleClick(View view) {
        super.handleClick(view);
        //your code goes here

    }
}

Upvotes: 0

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