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I just have a quick question and that is why can't I set the callback method directly in setOnClickListener() but instead I have to set a class that implements onClickListener? by saying something like setOnClickListener(new onClickListener(){}) In this case I have to set an anonymous class that implements onClickListener.

AnotherRandomUser
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    because you cannot pass methods as arguements in java – Breavyn Nov 16 '15 at 01:23
  • Thanks for answering, but I am new to java so can you be a little bit more specific to why that is? – AnotherRandomUser Nov 16 '15 at 01:26
  • http://stackoverflow.com/questions/4685563/how-to-pass-a-function-as-a-parameter-in-java – Breavyn Nov 16 '15 at 01:27
  • Hey thanks for the link it sorta help, but in the link it doesn't describe why I can't use a method as an arguments. So I still don't understand – AnotherRandomUser Nov 16 '15 at 01:43
  • Because java is strictly an OOP language, passing functions as parameter is not an OOP concept, hence it is not allowed in the language. – Breavyn Nov 16 '15 at 01:46
  • @ColinGillespie true for android java, not so much for desktop http://stackoverflow.com/a/31685857 – zapl Nov 16 '15 at 01:47
  • Oh so that is the reason why you have to use a class containing the method as an argument but when you pass in a class like that how can the method get invoked? Don't class acts like a blue print and I have to create instance of that class and invoke the method of that instance? – AnotherRandomUser Nov 16 '15 at 01:50
  • You aren't passing in a class, you are passing an object, which is an already instantiated class. You can then access its methods same as any other object. – Breavyn Nov 16 '15 at 01:53
  • Oh ok that makes sense but I am just passing in an object without invoking the method so how does android knows to access the method when a button let say is press? – AnotherRandomUser Nov 16 '15 at 01:54
  • No, every version of java allows this. The only difference is the new Java 8 allows a few new things such as lambdas. Android allows only Java 6 and Java 7 – Breavyn Nov 16 '15 at 01:56
  • Oh ok that makes sense but I am just passing in an object without invoking the method because I when declaring an onClickListener all I am doing is setOnClickListener(new View.OnClickListener(){ onClick(){system.out.print("test")}} so how does android knows to access the method when a button let say is press because all I am doing is declaring an instance of a class but not telling the class to use the method. – AnotherRandomUser Nov 16 '15 at 02:02
  • It knows that your object has implemented the `onClick` method so it simply calls it once it sees fit. IOW, It specified that you need to implement the onClick method since it defined that it needs a listener with that type. – zapl Nov 16 '15 at 02:03
  • Thanks for answering. I understand it now. – AnotherRandomUser Nov 16 '15 at 02:06

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