执行时出现Android AsyncTask错误

Question

This is my class to get Json from an url :

public class Json extends AsyncTask<Void , Void, JSONObject > {

String theUrl;
public AsyncResponse delegate = null;
InputStream is = null;
String result = "";
JSONObject jsonObject = null;
StringBuilder stringBuilder;
URLConnection urlConnection;
BufferedReader reader;

public Json(String theUrl , AsyncResponse delegate) {
   this.theUrl = theUrl;
   this.delegate = delegate;
}


public interface AsyncResponse {
    void processFinish(JSONObject output);
}


@Override
protected JSONObject doInBackground(Void... params) {
    try {
        URL url = new URL(theUrl);
        urlConnection = url.openConnection();

    } catch(Exception e) {
        Log.d("Fff22", " " +e);
        return null;
    }
    // Read response to string
    try {
        reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }

        result = sb.toString();

    } catch(Exception e) {

        return null;
    }

    // Convert string to object
    try {
        jsonObject = new JSONObject(result);
    } catch(JSONException e) {
        return null;
    }

    return jsonObject;
}



@Override
protected void onPostExecute(JSONObject jsonObject) {
     delegate.processFinish(jsonObject);
}

@Override
protected void onProgressUpdate(Void... values) {
    super.onProgressUpdate(values);
}

@Override
protected void onCancelled(JSONObject jsonObject) {
    super.onCancelled(jsonObject);
}

@Override
protected void onCancelled() {
    super.onCancelled();
}


 }

And in my actiivty I call it like this :

 String s = "http://192.168.0.106/json/259616167dfea1870e4d0330caa0323b.json";

     Json fs = new Json(s, new Json.AsyncResponse(){
         @Override
         public void processFinish(JSONObject output) {
             Log.d("fwwwwwww ","   "+output);
         }
     }).execute();

But its be all on red color and show :

incompatible types

required Json class

found Anroid.os.asyncTask java.lang.void , java.lang.void , org.json.JSONObject

I have problem on asyncTask any help also I dont know if its good idea to get json file.

If there are another solution and its better please share it.

Answer 1

The return type of the AsyncTask.execute() method is always AsyncTask type, not your child class Json - that's why you get your error.

So it should be

AsyncTask<Void, Void, JSONObject> fs = new Json(s, new Json.AsyncResponse(){
...

Answer 2

I think you have two obvious problems, here:

1. delegate is accessed from several threads, without synchronization. That is incorrect.
2. you call delegate.processFinished in onPreExecute . I think you intend to call it in onPostExecute

As for the Incompatible Type error, it is hard to tell, because there is neither any class in your listing, called MyJson , nor is there a complete error message.

Answer 3

Look at this question and my answer I believe that it'll help you a lot. Since the AsyncTask is no longer used for http request.