Question

I have this code:


        public class MainActivity extends Activity {
            // Declare Variables
            JSONObject jsonobject;
            JSONArray jsonarray;
            ListView listview;
            ListViewAdapter adapter;
            ProgressDialog mProgressDialog;
            ArrayList<HashMap<String, String>> arraylist;
            static String NAME = "rank";
            static String TYPE = "country";
            static String FLAG = "flag";

            @Override
            public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                // Get the view from listview_main.xml
                setContentView(R.layout.activity_main);
                // Execute DownloadJSON AsyncTask
                new DownloadJSON().execute();
            }

            // DownloadJSON AsyncTask
            private class DownloadJSON extends AsyncTask<Void, Void, Void> {

                @Override
                protected void onPreExecute() {
                    super.onPreExecute();
                    // Create a progressdialog
                    mProgressDialog = new ProgressDialog(MainActivity.this);
                    // Set progressdialog title
                    mProgressDialog.setTitle("Android JSON Parse Tutorial");
                    // Set progressdialog message
                    mProgressDialog.setMessage("Loading...");
                    mProgressDialog.setIndeterminate(false);
                    // Show progressdialog
                    mProgressDialog.show();
                }
                @Override
                protected Void doInBackground(Void... params) {
                    // Create an array
                    arraylist = new ArrayList<HashMap<String, String>>();
                    // Retrieve JSON Objects from the given URL address
                    jsonobject = JSONParser
                            .getJSONfromURL("http://54.218.73.244:7002/");

                    try {
                        // Locate the array name in JSON
                        jsonarray = jsonobject.getJSONArray("restaurants");

                        for (int i = 0; i < jsonarray.length(); i++) {
                            HashMap<String, String> map = new HashMap<String, String>();
                            jsonobject = jsonarray.getJSONObject(i);
                            // Retrive JSON Objects
                           map.put(MainActivity.NAME, jsonobject.getString("restaurantNAME"));
        map.put(MainActivity.TYPE, jsonobject.getString("restaurantTYPE"));
        //map.put(MainActivity.FLAG, jsonobject.getString("restaurantIMAGE"));
                            // Set the JSON Objects into the array
                            arraylist.add(map);
                        }
                    } catch (JSONException e) {
                        Log.e("Error", e.getMessage());
                        e.printStackTrace();
                    }
                    return null;
                }

                @Override
                protected void onPostExecute(Void args) {
                    // Locate the listview in listview_main.xml
                    listview = (ListView) findViewById(R.id.listview);
                    // Pass the results into ListViewAdapter.java
                    adapter = new ListViewAdapter(MainActivity.this, arraylist);
                    // Set the adapter to the ListView
                    listview.setAdapter(adapter);
                    // Close the progressdialog
                    mProgressDialog.dismiss();
                }
            }
        }

ListViewAdapter.java：

public abstract class ListViewAdapter extends BaseAdapter {

    // Declare Variables
    Context context;
    LayoutInflater inflater;
    ArrayList<HashMap<String, String>> data;
    //ImageLoader imageLoader;
    HashMap<String, String> resultp = new HashMap<String, String>();

    public ListViewAdapter(Context context,
            ArrayList<HashMap<String, String>> arraylist) {
        this.context = context;
        data = arraylist;
      //  imageLoader = new ImageLoader(context);
    }

    @Override
    public int getCount() {
        return data.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    public View getView(final int position, View convertView, ViewGroup parent) {
        // Declare Variables
        TextView rank;
        TextView country;
        //ImageView flag;

        inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View itemView = inflater.inflate(R.layout.listview_item, parent, false);
        // Get the position
        resultp = data.get(position);

        // Locate the TextViews in listview_item.xml
        rank = (TextView) itemView.findViewById(R.id.rank);
        country = (TextView) itemView.findViewById(R.id.country);

        // Locate the ImageView in listview_item.xml
        //flag = (ImageView) itemView.findViewById(R.id.flag);

        // Capture position and set results to the TextViews
        rank.setText(resultp.get(MainActivity.NAME));
        country.setText(resultp.get(MainActivity.TYPE));
        // Capture position and set results to the ImageView
        // Passes flag images URL into ImageLoader.class
      //  imageLoader.DisplayImage(resultp.get(MainActivity.FLAG), flag);
        // Capture ListView item click
        itemView.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // Get the position
                resultp = data.get(position);
                Intent intent = new Intent(context, SingleItemView.class);
                // Pass all data rank
                intent.putExtra("name", resultp.get(MainActivity.NAME));
                // Pass all data country
                intent.putExtra("type", resultp.get(MainActivity.TYPE));
                // Pass all data flag
               // intent.putExtra("flag", resultp.get(MainActivity.FLAG));
                // Start SingleItemView Class
                context.startActivity(intent);

            }
        });
        return itemView;
    }
}

And it gives an Error:

    Cannot instantiate the type ListAdapter

Why am i getting this error? A little help would be appreciated.

Answer 1

我相信您应该在活动的onCreate（）中初始化列表视图。也许你可以试试。

Answer 2

你的listadapter是一个抽象类，这就是为什么你得到错误使该类公开

ListViewAdapter未初始化

2 个答案: