android - 在 Android ListView 中显示来自 Json String 的数据

Question

我有一个如下所示的 JSON 字符串:

{"orders":[{"orderid":"561","order_date":"2016-05-04 09:23:18"},{"orderid":"560","order_date":"2016-05-04 08:56:33"}],"success":1}

我想在 Fragment Activity 的 ListView 中显示它。这是此 fragment 的代码:

public class PastOrders extends Fragment {

    private String jsonResult;
    private String url = "https://www.example.com/orders.php";
    private ListView listView;


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.past_orders, container, false);

        listView = (ListView) v.findViewById(R.id.listView1);

        accessWebService();

        return v;
    }

    // Async Task to access the web
    private class JsonReadTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... params) {
            HashMap<String,String> data = new HashMap<>();
            data.put("user_id",params[0]);
            data.put("status",params[1]);

            RegisterUserClass ruc = new RegisterUserClass();

            String result = ruc.sendPostRequest(url,data);

            jsonResult = result;

            return null;
        }

        private StringBuilder inputStreamToString(InputStream is) {
            String rLine = "";
            StringBuilder answer = new StringBuilder();
            BufferedReader rd = new BufferedReader(new InputStreamReader(is));

            try {
                while ((rLine = rd.readLine()) != null) {
                    answer.append(rLine);
                }
            }

            catch (IOException e) {
                // e.printStackTrace();
                Toast.makeText(getActivity().getApplicationContext(),
                        "Error..." + e.toString(), Toast.LENGTH_LONG).show();
            }
            return answer;
        }

        @Override
        protected void onPostExecute(String result) {
            ListDrwaer();
        }
    }// end async task

    public void accessWebService() {
        JsonReadTask task = new JsonReadTask();
        // passes values for the urls string array
        task.execute(new String[] { url });
    }

    // build hash set for list view
    public void ListDrwaer() {
        List<Map<String, String>> employeeList = new ArrayList<Map<String, String>>();

        try {
            JSONObject jsonResponse = new JSONObject(jsonResult);
            JSONArray jsonMainNode = jsonResponse.optJSONArray("orders");

            for (int i = 0; i < jsonMainNode.length(); i++) {
                JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
                String name = jsonChildNode.optString("orderid");
                String number = jsonChildNode.optString("order_date");
                String outPut = name + "-" + number;
                employeeList.add(createEmployee("orders", outPut));
            }
        } catch (JSONException e) {
            Toast.makeText(getActivity().getApplicationContext(), "Error" + e.toString(),
                    Toast.LENGTH_SHORT).show();
        }

        SimpleAdapter simpleAdapter = new SimpleAdapter(this, employeeList,
                android.R.layout.simple_list_item_1,
                new String[] { "orders" }, new int[] { android.R.id.text1 });
        listView.setAdapter(simpleAdapter);
    }

    private HashMap<String, String> createEmployee(String name, String number) {
        HashMap<String, String> employeeNameNo = new HashMap<String, String>();
        employeeNameNo.put(name, number);
        return employeeNameNo;
    }
}

我在以下几行中遇到错误:

SimpleAdapter simpleAdapter = new SimpleAdapter(this, employeeList,
                android.R.layout.simple_list_item_1,
                new String[] { "orders" }, new int[] { android.R.id.text1 });
        listView.setAdapter(simpleAdapter);

它说 SimpleAdapter 不能应用于我正在使用的这个类。

这是我遇到的错误:

Answer 1

尝试用 getActivity() 代替这个

SimpleAdapter simpleAdapter = new SimpleAdapter(getActivity(), employeeList,
                android.R.layout.simple_list_item_1,
                new String[] { "orders" }, new int[] { android.R.id.text1 });
        listView.setAdapter(simpleAdapter);

理解为什么这行不通也很重要。第一个参数需要是上下文。如果这是一个 Activity ，这可能会起作用，因为它指的是父对象，并且在 Activity 中它将为您提供上下文。但是在 fragment 内部你不能用它来获取上下文。您可以通过调用 getACtivity() 获取 fragment 内的上下文。在不同的情况下，您必须确保提供正确的上下文!!