overriding

问题 I would like to create a CustomButton which has a predefined onClick . In fact, my object would do the same job than CustomButton mButton = getViewById(..); mButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { show_something() } Is there a way to embed the Listener into the CustomButton object that inherits from Button ? What I would like is to create a CustomButton in my layout XML file, and not having to mention this button in my activity, which would

问题 When using some framework/api, sometimes it's pretty unclear if you must call base.Method if you override it, for example you can be pretty sure that you should call base.Maethod() when you are overriding event invocater, to propagate the event, in other situations it can be not so clear especially when there is no source code available, and no comments. I wounder how other programmers decide should they call base method or not in this situation, and if you are about to write some framework

问题 What i know is, the compiler writes a default no argument constructor in the byte code. But if we write it ourselves, that constructor is called automatically. Is this phenomena a constructor overriding? 回答1: What you describe isn't overriding. If you don't specify a default constructor, the compiler will create a default constructor. If it's a subclass, it will call the default parent constructor(super()), it will also initialize all instance variables to a default value determined by the

问题 I was reading 'Dive Into Python' and in the chapter on classes it gives this example: class FileInfo(UserDict): "store file metadata" def __init__(self, filename=None): UserDict.__init__(self) self["name"] = filename The author then says that if you want to override the __init__ method, you must explicitly call the parent __init__ with the correct parameters. What if that FileInfo class had more than one ancestor class? Do I have to explicitly call all of the ancestor classes' __init__

问题 To clarify- To my understanding, the methods below are all override of Object.equals . Are they overloading instead and I am not understanding this correctly? I'm running this code: public class AA { private int _val=0; public AA() { _val=5; } } public class BB extends AA { public BB() { .... } public boolean equals(BB ob) { return false; } public boolean equals(Object ob) { return true; } public boolean equals(AA ob) { return true; } public static void main(String args[]) { AA a2=new BB();

问题 using namespace std; #include <cstdio> #include <iostream> class One{ private: virtual void func(){ cout<<"bark!"<<endl; } }; class Two: public One{ public: void func(){ cout<<"two!"<<endl; } }; int main(){ One *o = new Two(); o->func(); } Why is there an error on o->func() ? I don't know the mechanism behind it... In my opinion, o->func() should call the func() in the derived class, which is public, so there wouldn't be problems, but it says: error: ‘virtual void One::func()’ is private 回答1:

问题 I'm trying to figure out how to override the dataGridHeader style defined in DataGrid.css! GWT core. The GWT style name is obfuscated with adler32 so I can't simply use .dataGridHeader in my css. In my case I wish a simple change of white-space:normal. I've seen may articles here about injecting css but they all appear to be class level rather than a sub style used within a component like DataGrid. How do I override a header style used within a component like DataGrid? 回答1: Just like with any

问题 I'm working on a web app that has a topBar similar to facebook's blue bar at the top. I have an unordered list within the div of that bar to list some items, like Inbox, Notifications, etc. The UL has a 1em margin as defined by the user agent stylesheet of my browser. This is a problem because it's pushing my topBar down 1em. How can I override this to make the border of the ul = 0? I've read that overriding user agent stylesheets is a bad idea so I'm curious to learn what is best to do.

问题 Let's take this simple Java code: public class Animal { public void eat() { System.out.println("Generic Animal Eating Generically"); } } public class Horse extends Animal { public void eat() { System.out.println("Horse eating hay "); } public void eat(String s) { System.out.println("Horse eating " + s); } } I'm trying to figure out which version of the three eat() methods will run. Now, when I type Animal a = new Animal(); a.eat(); The output is "Generic Animal Eating Generically", which is

问题 Given the following code (without virtual inheritance) : class A { public: virtual void f() = 0; }; class B : public A { public: virtual void f() {} }; class C : public A { public: virtual void f() {} }; class D : public B, public C { /* some code */ }; int main() { D d; return 0; } the code compile. On the other hand , here : class A { public: virtual void f() = 0; }; class B : virtual public A { virtual void f() {} }; class C : virtual public A { virtual void f() {} }; class D : public B,