Best way to get a variable in an Activity class from a class that is in a different package?

Question

I have class A which extends the Activity class. This class is in package aaa. I have class B which is in package aaa.extensions. What is the best way to access variables in class A?

Answer 1

如果您的类B是在类A中创建的，则通常可以通过将类A的实例传递给类B的构造函数来解决，因此类B的新实例可以在内部使用类A的实例。

Answer 2

Either I am not understanding well the question or it is really basic. What you need to do is provide access methods in your class A so any other class in whatever package it is could have access to that "variable" declared inside your class A by just giving an instance of A to any other class that wants/needs to access its internal state.

class A {
   private String name;  // internal private attribute (variable) for class A

   public String getName() {  // public access method for attribute "name"
       return name;
   }
}

class B {
   private A instanceOfA;   // internal private reference to class A

   public B(A instanceOfA) {   // public constructor of class B, which requires an instance of A as a parameter
        this.instanceOfA = instanceOf;
   }

   public void doNothing() {  // example method accessing A's attribute "name"
         System.out.println(instanceOfA.getName());
   }
}