Want to create a Generic AsyncTask

问题

In my project. For almost every Activity I have to make an AsyncTask .. And Almost the work is same for all of them. I want to create a generic AsyncTask and extends it. And i also want to send the methods in the constructor like this. Then Whenever I a class extends it . Just it have to create a method and it will do our work easily . and less coding .. It is time consuming .. Thanks for help in Advance..

One of my asyncTask is

private class GetData extends AsyncTask<String, Void, JSONObject> {

    @Override
    protected void onPreExecute() {
    super.onPreExecute();

    progressDialog = ProgressDialog.show(Calendar.this,
            "", "");

}

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

    String response;

    try {

        HttpClient httpclient = new DefaultHttpClient();

        HttpPost httppost = new HttpPost(url);

        HttpResponse responce = httpclient.execute(httppost);

        HttpEntity httpEntity = responce.getEntity();

        response = EntityUtils.toString(httpEntity);

        Log.d("response is", response);

        return new JSONObject(response);

    } catch (Exception ex) {

        ex.printStackTrace();

    }

    return null;
}

@Override
protected void onPostExecute(JSONObject result) 
{
    super.onPostExecute(result);

    progressDialog.dismiss();

    if(result != null)
    {
        try
        {
            JSONObject jobj = result.getJSONObject("result");

            String status = jobj.getString("status");

            if(status.equals("true"))
            {
                JSONArray array = jobj.getJSONArray("data");

                for(int x = 0; x < array.length(); x++)
                {
                    HashMap<String, String> map = new HashMap<String, String>();

                    map.put("name", array.getJSONObject(x).getString("name"));

                    map.put("date", array.getJSONObject(x).getString("date"));

                    map.put("description", array.getJSONObject(x).getString("description"));

                    list.add(map);
                }

                CalendarAdapter adapter = new CalendarAdapter(Calendar.this, list);

                list_of_calendar.setAdapter(adapter);
            }
        }
        catch (Exception e) 
        {
            e.printStackTrace();
        }
    }
    else
    {
        Toast.makeText(Calendar.this, "Network Problem", Toast.LENGTH_LONG).show();
    }
}

}

I just want to change the code in the post execute for each AsyncTask.. If I create a generic class and pass the Particular Method to it. It will be very helpful..

回答1:

let all your activities implements an interface say Ixxx, that has a method, activityOnPostExecute(String json), and pass the caller activity at the asyncTask constructor as type Ixxx, GenerucTask(Ixxx caller), and at postExecute() of the GenerucTask invoke caller.activityOnPostExecute(result); now at every activity override the method activityOnPostExecute().

EDIT: here is waht i mean

1- Create the interface that all activities should implement, with the onPoseExec() method:

public interface IAsyncHandler {
    public void onPostExec(String json);
}

2- Create the GenericAsyncTask class,

public class GenericAsyncTask extends AsyncTask<String, Integer, String> {
    IAsyncHandler handler = null;
    public GenericAsyncTask(IAsyncHandler h){
        handler = h;
    }
    @Override
    protected void onPreExecute() {

    }   
    @Override
    protected String doInBackground(String... params) {
        //whatever work goes here ...
        //return str as a result
        return str;
    }
    @Override
    protected void onPostExecute(String result) {
    //call the caller's class onPostExec(), it should be ovedrridden in the activity
        handler.onPostExec(result);
    }
}//CLASS

3- At your activity, override the method onPostExec()

@Override
public void onPostExec(String json) {
    // TODO Auto-generated method stub
}

4- At your activity onClick(), or somewhere execute the GenericAsyncTask

onClick(View v){
    GenericAsyncTask task = new GenericAsyncTask(this);
    task.execute("some", "params","...");
}

来源：https://stackoverflow.com/questions/23680546/want-to-create-a-generic-asynctask