在Android / java中调用类的私有对象的方法

Question

I have the following class:

public class Foo {
    private View myButton;
    ...
}

I'd like to call foo.myButton.performClick(). But I can't modify the Foo class since it is a library. How can I do it?

I'm trying with

Field mField= Foo.class.getDeclaredField("myButton");

but I don't know how to get the View reference from the Field

Thanks

Answer 1

With

Field mField = Foo.class.getDeclaredField("myButton")

you will get the reference of the specification of the field. Data included there is the accessors, the type of the value it holds, etc.. If you want to get the reference of the view you need to do the following:

View viewReference = (View)mField.get(fooInstance);

To access private fields (with reflection like mentioned below), you need to make sure the field is accessible:

mField.setAccessible(true);

I would recommend to restore the flag once you got the reference. Depending on the scenario you are facing, probably there is a better solution.

Good Luck

Answer 2

There's no way to use/get private fields or methods. That's java rule. You can't inherit a private field/method. Private methods/fields are restricted within the class they are defined.

Answer 3

There must be a better answer than breaking into the instance to get at its private information. The information is almost certainly private for a reason .

However, you can do it, using get like this (after your code getting mField ):

mField.setAccessible(true);
View button = (View)mField.get(theFooInstance);

(You need the setAccessible call because by default private fields are not accessible.)

Answer 4

You may need to set the accesible to true on that field before actually getting it:

Field field = Foo.getClass().getDeclaredField("myButton"));
      field.setAccessible(true);
View button = (View) field.get(fooInstance);

Answer 5

i think you could try to do it via java reflection. smth similar to:

Foo obj = new Foo();

Method method = obj.getClass().getDeclaredMethod( methodName );
method.setAccessible(true);

Object result = method.invoke(obj);