Most of the time you need to create a Service to perform something in the background, and your visible Activity simply controls this Service. (I’m sure the Music player works in the same way, so the example in the docs seems a bit misleading.) If that’s the case, then your Activity can finish as usual … Read more
I always find things like this more easily understood with pictures: Again, taking joseph daigle’s code, public class Foo { public /*virtual*/ bool DoSomething() { return false; } } public class Bar : Foo { public /*override or new*/ bool DoSomething() { return true; } } If you then call the code like this: Foo … Read more
It’s definitely “supported”. It is your web page, you do whatever you want to with it. I already did this to track analytics events without modifying a library but by sneaking into events. Use the proxy pattern: (function(proxied) { window.alert = function() { // do something here return proxied.apply(this, arguments); }; })(window.alert); You can also … Read more
The override modifier may be used on virtual methods and must be used on abstract methods. This indicates for the compiler to use the last defined implementation of a method. Even if the method is called on a reference to the base class it will use the implementation overriding it. public class Base { public … Read more
When you make a variable of the same name in a subclass, that’s called hiding. The resulting subclass will now actually have both properties. You can access the one from the superclass with super.var or ((SuperClass)this).var. The variables don’t even have to be of the same type; they are just two variables sharing a name, … Read more
In Java, the equals() method that is inherited from Object is: public boolean equals(Object other); In other words, the parameter must be of type Object. This is called overriding; your method public boolean equals(Book other) does what is called overloading to the equals() method. The ArrayList uses overridden equals() methods to compare contents (e.g. for … Read more
The clearest way to express polymorphism is via an abstract base class (or interface) public abstract class Human{ … public abstract void goPee(); } This class is abstract because the goPee() method is not definable for Humans. It is only definable for the subclasses Male and Female. Also, Human is an abstract concept — You … Read more
The below only works if the iframe content is from the same parent domain. The following jquery script works for me. Tested on Chrome and IE8. The inner iframe references a page that is on the same domain as the parent page. In this particular case, I am hiding an element with a specific class … Read more
Overriding depends on having an instance of a class. The point of polymorphism is that you can subclass a class and the objects implementing those subclasses will have different behaviors for the same methods defined in the superclass (and overridden in the subclasses). A static method is not associated with any instance of a class … Read more
Calling virtual functions from a constructor or destructor is dangerous and should be avoided whenever possible. All C++ implementations should call the version of the function defined at the level of the hierarchy in the current constructor and no further. The C++ FAQ Lite covers this in section 23.7 in pretty good detail. I suggest … Read more