java - 在 fragment 中的回调中获取异步任务结果

Question

我刚刚开始使用 android，无法弄清楚如何在 fragment 中获取 http json 响应。在我的 Activity 中，我可以轻松地使用回调函数来做到这一点，但在 fragment 中似乎很难完成同样的任务。

任何帮助将非常感激。

//SaleFragment.java
public class SaleFragment extends Fragment{

public static final String ARG_CLIENT_NUMBER = "client_number";
private ListView salesListView;
private View rootView;

public SaleFragment() {
// Empty constructor required for fragment subclasses
}

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

       rootView = inflater.inflate(R.layout.fragment_sale, container, false);
            int i = getArguments().getInt(ARG_CLIENT_NUMBER);
            try{
                     SaleStackJSON sale_json = new SaleStackJSON();
                     sale_json.execute("http://test.url/getJson"); //url to retrieve json
                     // do processing on the result (I do not know how to retrieve them here after the request)

           }catch(Exception e){
                      //  resultView.setText(e.getMessage());
              }

        return rootView;
   }

我的 JSON 类如下:

// SaleStackJSON.java
public class SaleStackJSON   extends AsyncTask<String, Void, String>{

    InputStream is = null;
    String result = "";
    JSONArray jArray = null;
    String error_text="";
    JSONObject j = null;
    TextView resultView;

    @Override
    protected String doInBackground(String... urls) {

        // Download JSON data from URL
        try {
            HttpClient httpclient = new DefaultHttpClient();
            HttpGet httpget = new HttpGet(urls[0]);
            HttpResponse response = httpclient.execute(httpget);
            HttpEntity entity = response.getEntity();
            is = entity.getContent();

        } catch (Exception e) {
            Log.e("log_tag", "Error in http connection " + e.toString());
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            setResult(sb.toString());

            //     this.jArray = new JSONArray(result);
        } catch (Exception e) {
            Log.e("log_tag", "Error converting result " + e.toString());
        }


        return getResult();
    }


    public String getResult() {
        return result;
    }
    public void setResult(String result) {
        this.result = result;
    }
}

编辑 1:我使用以下代码来填充我的前端。 (显示结果)

        JSONArray jArray;
        ArrayList all_sales = new ArrayList();
        try {
            jArray = new JSONArray(result);
            int total_retail_outlets = jArray.length();
            //LinearLayout scrollable_sale_layout = (LinearLayout)findViewById(R.id.scrollable_sale_layout);
            for (int i = 0; i < total_retail_outlets; i++) {
                    JSONObject jObj = jArray.getJSONObject(i);

                    String customer_name = jObj.getString("name");
                    String created_at = jObj.getString("created_at");
                    String quantity = jObj.getString("quantity");
                    String billing_amount = jObj.getString("billing_amount");
                    String discount_percentage = jObj.getString("discount_percentage");
                    String discount = jObj.getString("discount");
                    String total = jObj.getString("total");
                    SalesItem salesData = new SalesItem();
                    salesData.setBilling_amount(billing_amount);
                    salesData.setCreated_at(created_at);
                    salesData.setCustomer_name(customer_name);
                    salesData.setDiscount(discount);
                    salesData.setDiscount_percentage(discount_percentage);
                    salesData.setQuantity(quantity);
                    salesData.setTotal(total);

                    all_sales.add(salesData);
                }

            salesListView.setAdapter(new CustomSaleListAdapter(getActivity(), all_sales));


        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

Answer 1

对于任何拼写错误，我们深表歉意；我的解决方案是:

首先，最好在 doInBackground 方法中处理您的响应，因为它可以使 UI 线程不那么繁忙，因此:

 public class SaleStackJSON   extends AsyncTask<String, Void,  ArrayList<SalesItem>>

并在 doInBackground 中执行如下操作:

@Override
protected String doInBackground(String... urls) {

    // Download JSON data from URL
    try {
        HttpClient httpclient = new DefaultHttpClient();
        HttpGet httpget = new HttpGet(urls[0]);
        HttpResponse response = httpclient.execute(httpget);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();

    } catch (Exception e) {
        Log.e("log_tag", "Error in http connection " + e.toString());
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();


        //     this.jArray = new JSONArray(result);
    } catch (Exception e) {
        Log.e("log_tag", "Error converting result " + e.toString());
    }

    ArrayList<SalesItem> all_sales = new ArrayList<SalesItem>();
    JSONArray jArray;
    try {
        jArray = new JSONArray(sb.toString());
        int total_retail_outlets = jArray.length();
        for (int i = 0; i < total_retail_outlets; i++) {
                JSONObject jObj = jArray.getJSONObject(i);

                String customer_name = jObj.getString("name");
                String created_at = jObj.getString("created_at");
                String quantity = jObj.getString("quantity");
                String billing_amount = jObj.getString("billing_amount");
                String discount_percentage = jObj.getString("discount_percentage");
                String discount = jObj.getString("discount");
                String total = jObj.getString("total");
                SalesItem salesData = new SalesItem();
                salesData.setBilling_amount(billing_amount);
                salesData.setCreated_at(created_at);
                salesData.setCustomer_name(customer_name);
                salesData.setDiscount(discount);
                salesData.setDiscount_percentage(discount_percentage);
                salesData.setQuantity(quantity);
                salesData.setTotal(total);

                all_sales.add(salesData);
            }
      } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();

    return all_sales;
}

现在让我们进行最后的更改:

 protected void onPostExecute( ArrayList<SalesItem> result) {

 salesListView.setAdapter(new CustomSaleListAdapter(getActivity(), result[0]));

}