android：ArrayAdapter 在 AsyncTask 中只执行一次

Question

I'm parsing a JSon file which has 5 football teams and each of them have played 4 games.
I created a Wrapper class OutputClass to store all the details of each team ie number of games played, won, drawn and lost.
Since there are 5 teams, I created a List of OutputClass . So after passing the value to onPostExecute , I invoke an adapter called FootballAdapter . This adapter is executed only one time.
Even if I change my position value to 2 or 3 in outputClassList.get(int position) , I get the same result in Toast as you can see in the image below.
I checked if the outputClassList is empty but its not. Objects is a list, that is passed from:

FootballAdapter adapter= new FootballAdapter(getApplicationContext(),R.layout.row,result);
        jsonList.setAdapter(adapter);

The above code is in onPostExecute method of AsyncTask .

public class JSONTask extends AsyncTask<String,String,List<OutputClass>> {

    @Override
    protected List<OutputClass> doInBackground(String... params) {
        HttpURLConnection connection=null;
        BufferedReader r=null;

        try {
            URL url=new URL(params[0]);

            connection=(HttpURLConnection)url.openConnection();
            connection.connect();
            InputStream stream= connection.getInputStream();
            r= new BufferedReader(new InputStreamReader((stream)));
            StringBuffer stringBuffer=new StringBuffer();
            String line="";
            while((line=r.readLine())!=null){
                stringBuffer.append(line);
            }

            String finalJSON=stringBuffer.toString();


            /// read and parse JSON file for desired output.....

            JSONObject parentObject= new JSONObject(finalJSON);

            // gets the name of all the objects namels alpha, bravo charlie etc etc
            JSONArray names=parentObject.names();

            // multiple objets for each team.....
            List<OutputClass> outputClassList =new ArrayList<>();

            String games[]=new String[4];
            int finalScore[]=new int[names.length()];
            int gd[]=new int[names.length()];
            int won[]=new int[names.length()];
            int draw[]=new int[names.length()];
            int lost[]=new int[names.length()];



            JSONObject[] mainObject=new JSONObject[names.length()];
            for(int i=0;i<names.length();i++){

                String teamName=names.getString(i);
                mainObject[i]=parentObject.getJSONObject(teamName);

                //outputClass[i].name=teamName;
                // Gets the game data for each game....

                games[0]=mainObject[i].getString("match_1");
                games[1]=mainObject[i].getString("match_2");
                games[2]=mainObject[i].getString("match_3");
                games[3]=mainObject[i].getString("match_4");

                // Calculates the final score and goal difference for each team.

                for(int j=0;j<4;j++) {
                    String score[] = games[j].split("-");
                    int score1 = Integer.parseInt(score[0]);
                    int score2 = Integer.parseInt(score[1]);

                    if (score1 > score2) {
                        finalScore[i] += 3;
                        won[i]++;
                    }
                    else if (score1 == score2) {
                        finalScore[i] += 1;
                        draw[i]++;
                    }else{
                        lost[i]++;
                    }
                    gd[i]+=score1-score2;

                }



                // Calculating the position based on final score and Goal Difference...

                OutputClass outputClass=new OutputClass();
                outputClass.goalDifference=gd[i];
                outputClass.draw=draw[i];
                outputClass.finalScore=finalScore[i];
                outputClass.lost=lost[i];
                outputClass.won=won[i];
                outputClass.played=4;
                outputClass.name=teamName;

                outputClassList.add(outputClass);


            }
            //Arrays.sort(outputClass,OutputClass.FinalScoreComparator);
            //Arrays.sort(outputClass,new OutputClass().FinalScoreComparator);
            Collections.sort(outputClassList,new OutputClass().FinalScoreComparator);

            Log.i(TAG,"Final Scre: "+outputClassList.get(0).finalScore+" won : "+outputClassList.get(0).won);
            Log.i(TAG,"Final Scre: "+outputClassList.get(1).finalScore+" won : "+outputClassList.get(1).won);
            Log.i(TAG,"Final Scre: "+outputClassList.get(2).finalScore+" won : "+outputClassList.get(2).won);
            Log.i(TAG,"Final Scre: "+outputClassList.get(3).finalScore+" won : "+outputClassList.get(3).won);
            //return stringBuffer.toString();
            return outputClassList;

        } catch (MalformedURLException e) {
            e.printStackTrace();
        }catch (IOException e){
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        } finally {
            if(connection != null)
                connection.disconnect();
            try {
                if(r!=null)
                    r.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return null;
    }


    @Override

    protected void onPostExecute(List<OutputClass> result){
        super.onPostExecute(result);

        FootballAdapter adapter= new FootballAdapter(getApplicationContext(),R.layout.row,result);
        jsonList.setAdapter(adapter);

        //to remove the button and text view after clicking them...
        imageButton.setVisibility(View.GONE);
        jsonData.setVisibility(View.GONE);
        //showing the list.....
        setContentView(jsonList);


    }


}

public class FootballAdapter extends ArrayAdapter<OutputClass>{

    private List<OutputClass> outputClassList;
    private int resource;
    private LayoutInflater inflater;

    public FootballAdapter(Context context, int resource, List<OutputClass> objects) {
        super(context, resource, objects);
        outputClassList = objects;
        this.resource=resource;
        inflater =(LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        if(convertView== null)
            convertView=inflater.inflate(R.layout.row,null);


        TextView rank;
        TextView played;
        TextView won;
        TextView lost;
        TextView draw;
        TextView gd;

        rank=(TextView)findViewById(R.id.rank);
        played=(TextView)findViewById(R.id.played);
        won=(TextView)findViewById(R.id.won);
        lost=(TextView)findViewById(R.id.lost);
        draw=(TextView)findViewById(R.id.draw);
        gd=(TextView)findViewById(R.id.gd);

        if(rank!=null)
            played.setText("Played: " + outputClassList.get(position).played);
        if(won!=null)
            won.setText("Won: " + outputClassList.get(position).won);
        if(lost!=null)
            lost.setText("Lost: " + outputClassList.get(position).lost);
        if(draw!=null)
            draw.setText("Draw: " + outputClassList.get(position).draw);
        if(gd!=null)
            gd.setText("Goal Diff: " + outputClassList.get(position).goalDifference);


        Toast toast=Toast.makeText(getApplicationContext(),"Played: "+outputClassList.get(4).played+"Won: "+outputClassList.get(4).won,Toast.LENGTH_LONG);
        toast.show();
        return convertView;
    }
}

This is the log file that i created ot check if the outputClassList is empty or not :

I/enpFootball: Final Scre: 8 won : 2
I/enpFootball: Final Scre: 7 won : 2
I/enpFootball: Final Scre: 7 won : 2
I/enpFootball: Final Scre: 5 won : 1

A snipped of ListView can be seen at the image below:

Answer 1

The problem is probably in the line

rank=(TextView)findViewById(R.id.rank);

ArrayAdapter does not have findViewById() (see ArrayAdapter Reference )

Since the above line is working, you probably have your FootballAdapter class defined as a nested class inside a context (eg Activity or Fragment) from which it is using the findViewById() method. In this case, you will be searching for the "first" widget with the specified id in the entire context. So, your adapter is infact executing for all the items in the list, but each time it is called, it overwrites the first widget (eg the first. R.id.rank, and the first R.id.played, etc.)

Try this instead

rank= (TextView) convertView.findViewById(R.id.rank);

This way you are referring to the TextView inside the List Item that the adapter is supposed to fill and not the first item in the entire context. (See View Reference )

Answer 2

尝试打印 postexecute() 的结果，看看你在 postupdate 中得到了什么，之后你就会知道问题到底是什么，如果你不能理解，那么再次发布一些关于你的响应和适配器的更多信息班级