Android：从单独的类文件中调用AsyncTask内部类

Question

I have a Class: TabsPagerFragmentActivity which hosts all of the tabs.

I then have a separate class: ShopsFragment which has an inner class which extends AsyncTask

I'm trying to call the .execute method on this inner class from the TabsPagerFragmentActivity however i'm getting a

 No enclosing instance of the type is accessible error.

Is there a way to call this inner class execute from the TabsPagerFragmentActivity? Basically i'm trying to change an image as soon as the user leaves this fragment.

Code:

public class AlternateImageView extends AsyncTask<String,Integer,Void>{

        @Override
        protected Void doInBackground(String... params) {

            return null;
        }

        @Override 
        protected void onProgressUpdate(Integer... progress) {

        }

        @Override
        protected void onPostExecute(Void v) {
                       //Do something 
                }
         }

Thanks

Answer 1

Something like this?

AlternateImageView alternateImageView = new TabsPagerFragmentActivity().new AlternateImageView();
alternateImageView.execute();

I would like to add that I'm not going to pass judgement on this as a good or bad idea.

Answer 2

This is how to declare your inner class:

public class AlternateImageView extends AsyncTask<String,Integer,Void>

To use this class from a different class file, you need to add the word static, as the following:

public static class AlternateImageView extends AsyncTask<String,Integer,Void>

Then you can use your class like this:

AlternateImageView task = new TabsPagerFragmentActivity.AlternateImageView();
task.execute();

Answer 3

Change

public class 

to

public static class

Answer 4

Declare your AsyncTask as a static class. A static inner class makes the class be treated on the same visibility of other classes at the top level of the package, but you get the organizational benefits of having it as an inner class. For example:

Class1
Class2
Class3
    >Inner1
Class4

To call Inner1 you would need to do new Class3().new Inner1() . If you make it static like this:

Class1
Class2
Class3
    >static Inner1
Class4

Then you can create it as you would any other class in the package like new Inner1()