Getting objects out of an inner class/listener

Question

I finally managed to get an object out of an AsyncTask (DogAsyncTask) with an interface/listener (DogListener):

public String fout(String url) {

    Dog d_in = new Dog("DogName");
    DogAsyncTask task = new DogAsyncTask(d_in);

    final String out = "";    <---Have tried but error for out becomes "The final local variable out cannot be assigned, since it is defined in an enclosing type"
    task.setDogListener(new DogListener()
    {
        @SuppressWarnings("unchecked")
        @Override
        public void DogSuccessfully(String data) {  <---The string I want to get
            Log.e("DogListened", data);
            out = data;
        }

        @Override
        public void DogFailed() {}
    });

    task.execute(url);
    return out;
}

My main activity calls this function (fout) and is supposed to get a String out of it. String data is already there and Log.e("DogListened", data); records it too. How can I return that outwards to my main activity? I have tried setting out = data and made out a final String on the outside but the "final local variable out cannot be assigned, since it is defined in an enclosing type" error comes up. How can I get around this?

Thanks

it was just a try since others have said declare as a final to get it out of the inner class — d.mc2, Jan 21 '12 at 10:49
well.. then I d suggest you declare it without the final keyword and declare it in the scope of your activity. Then you can access and change its value from within. — Orkun, Jan 21 '12 at 10:54
that's what I tried at first, however, it did not work out. Thanks a lot for your help though — d.mc2, Jan 21 '12 at 10:56

score 1 · Accepted Answer · edited May 23 '17 at 11:48

I guess you cannot access to out because it is out of the listener's scope. You can maybe pass your out as a reference parameter to the constructor of your DogListener.

final String out = "";    
task.setDogListener(new DogListener( **out** )
{
    @SuppressWarnings("unchecked")
    @Override
    public void DogSuccessfully(String data) {  
        Log.e("DogListened", data);
        out = data;
    }

    @Override
    public void DogFailed() {}
});

BUT honestly I donT know how to pass parameters as a reference in Java like in C#..

EDIT:

This can help you too: Can I pass parameters by reference in Java?

score 0 · Answer 2 · answered Jan 21 '12 at 10:44

Use a value holder, which basically is an object which stores some value in a field. The value holder can be assigned as final, but you can change the value. Follow the link for more info on this pattern: http://martinfowler.com/eaaCatalog/lazyLoad.html

However you can use your string as value holder: Just append to the empty string assigned to out. Or better use a StringBuffer object.

Getting objects out of an inner class/listener

2 Answers2