Android/Java: x in MainActivity cannot implement Y in Interface

Question

I'm new to Java and I can't seem to wrap my head around this one.

I am trying to fetch the contents of a web page (txt file) from a URL and add each line to an ArrayList.

I can spit the array out using Log.d in onPostExecute, but I would like to be able to return the ArrayList in MainActivity to then do some validation and pass the results onto another class for processing.

I have tried to follow this answer: How to get the result of OnPostExecute() to main activity because AsyncTask is a separate class?

I'm getting the following error:

Error:(25, 10) error: processFinish(ArrayList) in MainActivity cannot implement processFinish(ArrayList) in AsyncResponse attempting to assign weaker access privileges; was public

Any help would be greatly appreciated.

MainActivity:

package uk.co.mmotti.nothanks;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import java.util.ArrayList;

import uk.co.mmotti.nothanks.HostProcessing.fetchHosts;


public class MainActivity extends AppCompatActivity implements AsyncResponse {

    fetchHosts asyncFetchHosts = new fetchHosts();

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

        asyncFetchHosts.delegate = this;
        asyncFetchHosts.execute("https://exampletexturl.com/");
    }

    @Override

    /* THIS IS WHERE THE ERROR OCCURS ************************/
    void processFinish(ArrayList<String> output){
        //Here you will receive the result fired from async class
        //of onPostExecute(result) method.
    }

}

fetchHosts

package uk.co.mmotti.nothanks.HostProcessing;

import android.os.AsyncTask;
import android.util.Log;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;

import uk.co.mmotti.nothanks.AsyncResponse;

public class fetchHosts extends AsyncTask<String, Integer, ArrayList<String>> {

    public AsyncResponse delegate = null;

    @Override
    protected  ArrayList<String> doInBackground(String...hostUrl) {
        ArrayList<String> hosts = new ArrayList<>();

        try
        {
            // Set the URL to the host parameter
            URL url = new URL(hostUrl[0]);

            // Open a new stream to the url
            BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));

            // Clear any values that may already be in 'line'
            String readerLine = null;

            // Whilst there are still lines to output
            while((readerLine = in.readLine()) != null)
            {
                // Add host to array
                hosts.add(readerLine);
            }

            // Close stream when done
            in.close();
        }
        // On error exception
        catch (IOException e)
        {
            e.printStackTrace();
        }

        // Output to PostExecute
        return hosts;
    }

    protected void onPreExecute() {

    }

    protected void onProgressUpdate(Integer... values) {

    }

    @Override
    protected void onPostExecute(ArrayList<String> hosts) {
        //Log.d("MM: ", hosts.toString());
        delegate.processFinish(hosts);
    }
}

AsyncResponse (Separate class / interface)

package uk.co.mmotti.nothanks;

import java.util.ArrayList;


public interface AsyncResponse {
    void processFinish(ArrayList<String> output);
}

Thanks! How come it has to be public here but void in the AsyncResponse interface? — mmotti, Jan 22 '18 at 15:15

score 0 · Answer 1 · answered Jan 22 '18 at 15:04

0

just write public void processFinish(ArrayList<String> output){ instead of void processFinish(ArrayList<String> output){. The Method has to be public...

answered Jan 22 '18 at 15:04

Christoph Lembeck

54
2

score 0 · Answer 2 · answered Jan 22 '18 at 15:04

0

Change void processFinish(ArrayList<String> output) in your MainActivity class to public void processFinish(ArrayList<String> output)

answered Jan 22 '18 at 15:04

Chris Stillwell

10,266
10
67
77

Excellent - I can't mark as answer yet as it's too soon. What's the reason for it having to be public here when it's void in the interface? I still have much to learn. – mmotti Jan 22 '18 at 15:08
@mmotti read the duplicate post, and next time just google your error – Tim Jan 22 '18 at 15:16

Android/Java: x in MainActivity cannot implement Y in Interface

2 Answers2