Question

我使用自定义适配器将一些数据从JSON拉到我的ListView：

adapter = new ActorAdapter(this, R.layout.data_item, actorsList);

JSON包含5个项目。一切都很好，所有项目都显示，但是...因为我也使用位置服务，我需要更新ListView（距离等）。

这发生在这里：

       private void updateUI(Location loc) {
        double Act1=loc.getLatitude();
        double Act2=loc.getLongitude();

        ListView lv = findViewById(R.id.listView1);
        lv.setAdapter(adapter);
adapter.clear();adapter.notifyDataSetChanged();
        new GetContacts().execute();}

问题是，每次更新后，我的ListView都有相同的数据次数 - 重复。如您所见，我尝试使用adapter.clear();adapter.notifyDataSetChanged();

然而，这几乎没有问题，没有更多重复 - 但每次更新后，ListView总是只显示4个项而不是5个。

所以第一次ListView加载5个项目 - 好的，但是在接下来的每次更新后它只显示4个项目。这很奇怪，无法找到问题为什么......

附加我的GetContacts异步任务：

    class GetContacts extends AsyncTask<String, Void, Boolean> {
    ProgressDialog dialog;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        dialog = new ProgressDialog(Okoli.this);
        dialog.setMessage("Loading data");
        dialog.setTitle("Connecting");
        dialog.show();
        dialog.setCancelable(false);
    }

    @Override
    protected Boolean doInBackground(String... args) {
        HttpHandler sh = new HttpHandler();
        String url = "androidnews.json";
        String jsonStr = sh.makeServiceCall(url);Double myDistx;

        if (jsonStr != null) {
            try {JSONObject jsonObj = new JSONObject(jsonStr);
                JSONArray actors = jsonObj.getJSONArray("result");

                for (int i = 0; i < actors.length(); i++) {
                    JSONObject c = actors.getJSONObject(i);

                    Actors actor = new Actors();

                    double g1 = Double.parseDouble(c.getString("gps1"));
                    double g2 = Double.parseDouble(c.getString("gps2"));
                    double Act1=loc.getLatitude();
                    double Act2=loc.getLongitude();

                    myDistx = meterDistanceBetweenPoints(g1,g2,Act1,Act2);

                    actor.setNazov(c.getString("name"));
                    actor.setPerex(c.getString("perex"));
                    actor.setPlace(c.getString("place"));
                    actor.setGps1(c.getString("gps1"));
                    actor.setGps2(c.getString("gps2"));

                    actor.setDist(myDistx);

                    actorsList.add(actor);

                }

            }  catch (final JSONException e) {
              Okoli.this.runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(Okoli.this.getApplicationContext(),
                                "Data error: " + e.getMessage(),
                                Toast.LENGTH_LONG).show();
                    }
                }); }

            return true;

        } else {
             Okoli.this.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(Okoli.this.getApplicationContext(),
                            "Network error",
                            Toast.LENGTH_LONG).show();
                }
            });
            return false;
        }
    }

    protected void onPostExecute(Boolean result) {
        super.onPostExecute(result);
        dialog.dismiss();
        adapter.notifyDataSetChanged();
    }


}

以及我的适配器：

public class ActorAdapter extends ArrayAdapter<Actors> {
private Context context;
private ArrayList<Actors> actorList;
private LayoutInflater vi;
private int Resource;

ActorAdapter(Context context, int resource, ArrayList<Actors> objects) {
    super(context, resource, objects);
    this.context = context;
    vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    Resource = resource;
    actorList = objects; }

@NonNull
@Override
public View getView(final int position, View convertView, @NonNull final ViewGroup parent) {
    View v = convertView;
    ViewHolder holder;
    if (v == null) {
        holder = new ViewHolder();
        v = vi.inflate(Resource, null);
        holder.tvNazov = v.findViewById(R.id.tvNazov);
        holder.tvPlace = v.findViewById(R.id.tvPlace);
        holder.tvPerex = v.findViewById(R.id.tvPerex);
        holder.tvDist = v.findViewById(R.id.tvDist);
        v.setTag(holder);
    } else {
        holder = (ViewHolder) v.getTag();
    }

holder.tvNazov.setText(actorList.get(position).getNazov());
    holder.tvPlace.setText(actorList.get(position).getPlace());
    holder.tvPerex.setText(actorList.get(position).getPerex());

    String newDist = String.format("%.1f", actorList.get(position).getDist());
    holder.tvDist.setText(newDist);

    return v;
}

static class ViewHolder {

    TextView tvNazov;
    TextView tvPerex;
    TextView tvPlace;
    TextView tvDist;
    }
}

Answer 1

您的适配器将actorsList称为数据源，但此变量永远不会被清空。

更新适配器后，ListView显示更少的项目 - android

1 个答案: