Android java method - Can a parameter be more than one type?

Question

I'm new to java/android and would really appreciate help with this. I would like my java method to be able to take in more than one type for the parameter. For example the variable myButton could be an ImageButton or just a Button. The code inside myFunction is valid for whether myButton is an ImageButton or a Button.

if (condition) {
    ImageButton myButton = (ImageButton) findViewById(R.id.myButtonID);
    myFunction(myButton);
} else {
    Button myButton = (Button) findViewById(R.id.myButtonID);
    myFunction(myButton);
}

public void myFunction(Button or ImageButton myButton) {
    ....identical code for myButton which could be an ImageButton or Button....
}

I could obviously write out 2 funcions for parameter type and call it when applicable but that seems like a waste and there must be a quicker way. How can I do this? Thanks for your help.

Answer 1

If both classes have a common interface that can be used inside your method, you can use it and catch both types.

Otherwise, you can use overloading or generic method.

Answer 2

Depends on what the method does to the passed in parameter.

Usually, you'd use polymorphism . Looking at the inheritance graphs,

ImageButton extends ImageView extends View extends Object

and

Button extends TextView extends View extends Object

The most specific common superclass is View . If the method can work on View s, then you should specify the parameter type to be a View :

public void myFunction(View view) {
    //...
}

If the method does different things to ImageButton s and Button s, then you can use method overloading . That is, two methods that have take different parameters:

public void myFunction(ImageButton imageButton) {
    //...
}

public void myFunction(Button button) {
    //...
}

In rare cases, a generics -based solution could also work. Note that the compiler will actually generate copies of the code for each different type passed in, so you should prefer polymorphism-based solution when you can:

public <ParamType extends View> void myFunction(ParamType param) {
    //...
}

Answer 3

You should use common super class of the Button and ImageButton which is for example View and then:

public void myFunction(View view) {
    if(view instanceof Button) {
        Button btn = (Button) view;
        // do something with Button instance
    }

    if(view instanceof ImageButton) {
        ImageButton iBtn = (ImageButton) view;
        // do something with Image Button instance
    }
}