I'm making an Android app that makes use of AsyncTask to download some data. To make my code a bit more readable I re-created this code on a separate class ("ContentManager"). However, I don't know how to import it into my main activity.

Here's the code on my main activity, which doesn't work (error: "Cannot resolve symbol DownloadJson"):

```
public class MyApp extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_category_list);

        ContentManager contentManager = new ContentManager();
        ContentManager downloadJsonTask = new contentManager.DownloadJson();

        downloadJson.execute("http://.../api/...");

    }
}

```

And here's my AsyncTask code, that lives in a class file (ContentManager.java on the same package folder than the main activity):

```
public class ContentManager {

    // DownloadJson is a class that gets a JSON response given a url specified on the call
    public class DownloadJson extends AsyncTask<String,Void,String> {

        @Override
        protected String doInBackground(String... urls) {

            // Defined required variables
            String result = "";
            URL url;
            HttpURLConnection urlConnection = null;

            // Try to download content
            try {

                url = new URL(urls[0]);
                urlConnection = (HttpURLConnection)url.openConnection();

                InputStream in = urlConnection.getInputStream();
                InputStreamReader reader = new InputStreamReader(in);

                int data = reader.read();

                while (data != -1) {

                    char currentCharacter = (char)data;

                    result += currentCharacter;

                    data = reader.read();
                }
                return result;
            }
            catch(MalformedURLException e){
                e.printStackTrace();
            }catch(IOException e){
                e.printStackTrace();
            }
            return null;
        }
    }
}

```

How can I import an inner class from another file? Is this the correct way of doing it?