Android-如何使用在内部类上声明的变量？

Question

I have this method:

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        AnimalWebService animalWebService = restAdapter.create(AnimalWebService.class);

        Callback<List<Animal>> callback = new Callback<List<Animal>>() {
            @Override
            public void success(List<Animal> animals, Response response) {
                if (animals == null) {
                    Context context = getApplicationContext();
                    CharSequence text = "No animals available!";
                    int duration = Toast.LENGTH_SHORT;

                    Toast toast = Toast.makeText(context, text, duration);
                    toast.show();
                }
                else {
                    ListAdapter theAdapter = new MyAdapter(getApplicationContext(), animals);
                }
            }
            @Override
            public void failure(RetrofitError retrofitError) {
                return;
            }
        };

        animalWebService.get(callback);
        theListView.setAdapter(theAdapter);
    }

In the end I have theListView.setAdapter(theAdapter); but theAdapter is not recognized here since it was declared in an inner class.

How would I solve this? What are the best practices for this case when programming in Android?

Answer 1

If you don't need a reference to theAdapter in other parts of the Activity class, I would just update it from the callback:

    Callback<List<Animal>> callback = new Callback<List<Animal>>() {
        @Override
        public void success(List<Animal> animals, Response response) {
            if (animals == null) {
            }
            else {
                ListAdapter theAdapter = new MyAdapter(getApplicationContext(), animals);
                theListView.setAdapter(theAdapter);
            }
        }
        @Override
        public void failure(RetrofitError retrofitError) {
            return;
        }
    };

This ensures that you are never calling setAdapter(null) on the list view, which is good. You should trigger events depending on the outcome of the callback: your call might fail (then failure is called), or it could be returning an empty list. In those cases we don't want the ListView to be attached to the adapter.