当我们通过向下滑动更新列表视图时，如何防止在列表视图中显示重复值和重复值？

Question

我在我的应用程序中使用了列表视图。我使用滚动条来更新详细信息。我再次获得了完整的更新列表。它添加了 ny 列表中的所有数据。我想避免它，所以请建议我如何在更新后限制列表中的重复值......我的代码 sn-p 在这里......

public class MainActivity extends ListActivity implements  SwipeRefreshLayout.OnRefreshListener {

    private ProgressDialog pDialog;
    ListView mListView;
    SwipeRefreshLayout swipeLayout;
    Adapter mAdapter;

    // URL to get contacts JSON
    private static String url = "http://api.androidhive.info/contacts/";

    // JSON Node names
    private static final String TAG_CONTACTS = "contacts";
    private static final String TAG_ID = "id";
    private static final String TAG_NAME = "name";
    private static final String TAG_EMAIL = "email";
    private static final String TAG_ADDRESS = "address";
    private static final String TAG_GENDER = "gender";
    private static final String TAG_PHONE = "phone";
    private static final String TAG_PHONE_MOBILE = "mobile";
    private static final String TAG_PHONE_HOME = "home";
    private static final String TAG_PHONE_OFFICE = "office";

    // contacts JSONArray
    JSONArray contacts = null;

    // Hashmap for ListView
    ArrayList<HashMap<String, String>> contactList;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //  SwipeRefreshLayout mSwipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.activity_main_swipe_refresh_layout);

        swipeLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_container);
        swipeLayout.setOnRefreshListener(this);
        swipeLayout.setColorScheme(android.R.color.holo_blue_bright,
                android.R.color.holo_green_light,
                android.R.color.holo_orange_light,
                android.R.color.holo_red_light);


        contactList = new ArrayList<HashMap<String, String>>();

        ListView lv = getListView();

        // Listview on item click listener
        lv.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {
                // getting values from selected ListItem
                String name = ((TextView) view.findViewById(R.id.name))
                        .getText().toString();
                String cost = ((TextView) view.findViewById(R.id.email))
                        .getText().toString();
                String description = ((TextView) view.findViewById(R.id.mobile))
                        .getText().toString();

                // Starting single contact activity
                Intent in = new Intent(getApplicationContext(),
                        ak.class);
                in.putExtra(TAG_NAME, name);
                in.putExtra(TAG_EMAIL, cost);
                in.putExtra(TAG_PHONE_MOBILE, description);
                startActivity(in);

            }
        });

        // Calling async task to get json
       new GetContacts().execute();
    }

    /**
     * Async task class to get json by making HTTP call
     */
    private class GetContacts extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // Showing progress dialog
         //   pDialog = new ProgressDialog(MainActivity.this);
          //  pDialog.setMessage("Please wait...");
           // pDialog.setCancelable(false);
            //Dialog.show();

        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // Creating service handler class instance
            ServiceHandler sh = new ServiceHandler();

            // Making a request to url and getting response
            String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);

            Log.d("Response: ", "> " + jsonStr);

            if (jsonStr != null) {
                try {
                    JSONObject jsonObj = new JSONObject(jsonStr);

                    // Getting JSON Array node
                    contacts = jsonObj.getJSONArray(TAG_CONTACTS);

                    // looping through All Contacts
                    for (int i = 0; i < contacts.length(); i++) {
                        JSONObject c = contacts.getJSONObject(i);

                        String id = c.getString(TAG_ID);
                        String name = c.getString(TAG_NAME);
                        String email = c.getString(TAG_EMAIL);
                        String address = c.getString(TAG_ADDRESS);
                        String gender = c.getString(TAG_GENDER);

                        // Phone node is JSON Object
                        JSONObject phone = c.getJSONObject(TAG_PHONE);
                        String mobile = phone.getString(TAG_PHONE_MOBILE);
                        String home = phone.getString(TAG_PHONE_HOME);
                        String office = phone.getString(TAG_PHONE_OFFICE);

                        // tmp hashmap for single contact
                        HashMap<String, String> contact = new HashMap<String, String>();

                        // adding each child node to HashMap key => value
                        contact.put(TAG_ID, id);
                        contact.put(TAG_NAME, name);
                        contact.put(TAG_EMAIL, email);
                        contact.put(TAG_PHONE_MOBILE, mobile);

                        // adding contact to contact list
                        contactList.add(contact);
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            } else {
                Log.e("ServiceHandler", "Couldn't get any data from the url");
            }

            return null;
        }


        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            // Dismiss the progress dialog
           /* if (pDialog.isShowing())
                pDialog.dismiss();*/
            /**
             * Updating parsed JSON data into ListView
             * */
            ListAdapter adapter = new SimpleAdapter(
                    MainActivity.this, contactList,
                    R.layout.list_item, new String[]{TAG_NAME, TAG_EMAIL,
                    TAG_PHONE_MOBILE}, new int[]{R.id.name,
                    R.id.email, R.id.mobile});

            setListAdapter(adapter);


        }


    }



    @Override
    public void onRefresh() {
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                new GetContacts().execute();
                swipeLayout.setRefreshing(false);
            }
        }, 5000);

    }

Answer 1

您唯一需要做的就是像这样设置适配器，它不会复制数据。它只是在旧数据之下添加新数据。

           adapter = null;
                if (adapter == null) {

                        adapter = new CustomAdapter(this, arrayList);
                        listvie.setAdapter(adapter);

                    }
                    adapter.notifyDataSetChanged();

希望它会奏效。 谢谢。 :)

Answer 2

解决方法很简单。

1. 在使用空集合执行 AsyncTask 之前创建 ListAdapter
2. 使用创建的适配器为 ListView 设置适配器
3. 在AsyncTask中创建本地字段ArrayList<HashMap<String, String>> localList
4. 已解析的联系人放入 localList，而不是 contactList
5. 下载物品后，拨打contactList.clear();清除收藏
6. 添加下载联系人contactList.addAll(localList);
7. 致电adapter.notifyDataSetChanged();