Lint Leak Warning Calling Nested Static Asynctask

Issue

I am getting the following lint warning:

This AsyncTask class should be static or leaks might occur

Calling Class

private static Helper.GetRadar mTask;

private void setRadar(String area, String distance, String radar) {
    **/// LINT WARNING ON THE BELOW LINE**
     mTask = new Helper.GetRadar(activity, area, distance, radar) {
            @Override
            protected void onPostExecute(String result) {
                gotRadar(result);
            }
    };
}

Inner Static Async Task:

class Helper {    

....

    public static class GetRadar extends AsyncTask<String, Void, String> {
        private WeakReference<Context> mContext;

        GetRadar(Context context, String area, String distance, String radar) {
            mContext = new WeakReference<Context>(context);            
        }

        @Override
        protected String doInBackground(String... arg) {
        ....
        return result;
    }

    @Override
    protected void onPostExecute(String result) {
        /// Override
    }
}
}

Why am I getting this error when the class is already declared static?

Solution

You are extending the static class with an anonymous inner class, which will hold a reference to the calling activity, which is why you are getting that warning. You could create your own custom interface to call in onPostExecute, like this:

public static class GetRadar extends AsyncTask<String, Void, String> {
    private WeakReference<Context> mContext;
    private MyPostExecute mRunner;

    interface MyPostExecute {
        void run(String result);
    }

    GetRadar(Context context, String area, String distance, String radar, MyPostExecute runner) {
        mContext = new WeakReference<Context>(context);     
        mRunner = runner;            
    }

    @Override
    protected String doInBackground(String... arg) {
        ....
        return result;
    }

    @Override
    protected void onPostExecute(String result) {
        mRunner.run(result);
    }
}

Each class that wants to use the AsyncTask can define its own PostExecute implementation, like this:

private static MyRunner implements GetRadar.MyPostExecute {
    private WeakReference<Helper> mHelper;

    MyRunner(Helper h) {
        mHelper = new WeakReference<>(h);
    }

    @Override
    void run(String result)
    {
        Helper h = mHelper.get();
        if( h != null && !h.isFinishing() ) {
            h.gotRadar(result);
        }
    } 
}

Then for this case, you would call it with:

mTask = new Helper.GetRadar(activity, area, distance, radar, new MyRunner(this));

Answered By - Tyler V