Java: calling outer class method in anonymous inner class

Recently, I ran into a mysterious problem in an android project, which I described here. I somehow solved the problem, but still don't know the exact reason behind it.

Let's say I want to call a function foo() in the inner class. The question is, what's the difference between calling it directly like

foo();

or calling it with the outer class instance

OuterClass.this.foo();

Besides, i will appreciate if anyone can check my last question related to this, and give me a clue about why the error occurs. Many thanks.

PS: I read somewhere that the non-static inner class will always hold an instance of the outer class. So it will call outer function using that instance if I only use foo()?

Solution 1:

The latter is more explicit and will allow you to call the outer class method if one exists in the inner class with the same name.

class OuterClass {
    void foo() { System.out.println("Outer foo"); }

    View.OnClickListener mListener1 = new View.OnClickListener() {
        void foo() { System.out.println("Inner foo"); }

        @Override public void onClick(View view) {
            foo(); //Calls inner foo
            OuterClass.this.foo(); //Calls outer foo
        }
    }

    View.OnClickListener mListener2 = new View.OnClickListener() {
        @Override public void onClick(View view) {
            foo(); //Calls outer foo
            OuterClass.this.foo(); //Calls outer foo
        }
    }
}