Why Are My Inner Class AsyncTask's Data Changes Not Reflected in the Outer Class?

Inner Class Data Modification in AsyncTask

In this scenario, you have an inner class, Decompress, which extends AsyncTask and attempts to modify member variables of its enclosing class, Unzip. However, these changes appear to be lost when accessed from the outer class.

Data Updation

The problem stems from the fact that AsyncTask operates asynchronously, meaning it runs in a separate thread. While modifications to member variables will still persist in the class, they may not be reflected immediately in the enclosing class due to the thread separation. To ensure the outer class can access the updated values, a callback mechanism can be implemented.

Callback Interface

One solution is to create an interface with a method that will be called back when the inner class has completed its task and updated the values. In your example, you could define an interface like the following:

public interface InnerClassUpdateListener {
    void onInnerClassUpdate(String index, String unzipDest);
}

Implementation

In the Decompress class, implement the onInnerClassUpdate method within the AsyncTask. This method would be called when the inner class has finished its task and the values have been updated. In your doInBackground method, add the code:

if (unzip operation is successful) {
    result = true;
    index = url pointing to location of unzipped folder;
    unzipDest = something; //unzip destination is set here
    if (callback != null) {
        callback.onInnerClassUpdate(index, unzipDest);
    }
}

In the Unzip class, register as a listener to the callback. For example:

Decompress decompress = new Decompress(location, activity);
decompress.setCallback(new InnerClassUpdateListener(){
    @Override
    public void onInnerClassUpdate(String index, String unzipDest) {
        // Update your outer class variables here
    }
});

Thread Considerations

As you correctly noted, AsyncTask runs in a separate thread. This means that any values updated in this thread will remain within that thread until the task completes. However, once the task completes and the onPostExecute method is called, the updated values will be available to the enclosing class. By implementing a callback, you can ensure that the outer class can access the updated values when they become available.

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