Difference between OnClick() event and OnClickList

Question

I'm always using onclick() event in most of my projects. But, I read about OnClickListener(). Can anyone tell what's the difference between these two? And which one is best to use in Android application?.

Answer 1

There are a couple reasons why you might want to programmatically set an OnClickListener. The first is if you ever want to change the behavior of your button while your app is running. You can point your button at another method entirely, or just disable the button by setting an OnClickListener that doesn't do anything.

When you define a listener using the onClick attribute, the view looks for a method with that name only in its host activity. Programmatically setting an OnClickListener allows you to control a button's behavior from somewhere other than its host activity. This will become very relevant when we learn about Fragments, which are basically mini activities, allowing you to build reusable collections of views with their own lifecycle, which can then be assembled into activities. Fragments always need to use OnClickListeners to control their buttons, since they're not Activities, and won't be searched for listeners defined in onClick.

Answer 2

I am assuming by onClick that you use is the one that you defines in XML Layout. These two are alternative that serve same function but implemented differently.

1. The onClick with function binding in XML Layout is a binding between onClick and the function that it will call. The function have to have one argument (the View) in order for onClick to function.

2. An OnClickListener is an interface that any class could implement. Since it is an interface that any class could implement, this has more flexibility and more complex in its form. Few flexibilities that you could have with OnClickListener

   • You could easily swap one listener implementation with another if you need to.
   • An OnClickListener enable you to separate the action/behavior of the click event from the View that triggers the event. While for simple cases this is not such a big deal, for complex event handling, this could mean better readability and maintainability of the code
   • Since OnClickListener is an interface, the class that implements it has flexibilities in determining the instance variables and methods that it needs in order to handle the event. Again, this is not a big deal in simple cases, but for complex cases, we don't want to necessary mix up the variables/methods that related to event handling with the code of the View that triggers the event.

Answer 3

We use

    public void button_onClick_name(View v)
{
-------
}

to define a method out of the class. But To define a component Click event within a class, we use onclick listener.

Answer 4

OnClickListener is what waits for someone to actually click, onclick determines what happens when someone clicks

the listener is a class, the onclick is a method, this distinction is not very useful in simple cases, but if you want to be more complicated it becomes more necessary

Answer 5

OnClickListener is the interface you need to implement and can be set to a view in java code.

Lately android added a xml attribute to views called android:onclick, that can be used to handle clicks directly in the view's activity without need to implement any interface.

Both function the same way, just that one gets set through java code and the other through xml code.

Answer 6

There are a couple reasons why you might want to programmatically set an OnClickListener. The first is if you ever want to change the behavior of your button while your app is running. You can point your button at another method entirely, or just disable the button by setting an OnClickListener that doesn't do anything.

When you define a listener using the onClick attribute, the view looks for a method with that name only in its host activity. Programmatically setting an OnClickListener allows you to control a button's behavior from somewhere other than its host activity. This will become very relevant for Fragments, Fragments always need to use OnClickListeners to control their buttons, since they're not Activities, and won't be searched for listeners defined in onClick.