android - ProgressDialog、RunOnUiThread 和 ListAdapter 的问题

Question

好吧，我已经编写了这个 Android 程序，它有 3 个选项卡(餐食、饮料和甜点)，每个选项卡都有一个 fragment 在自己的 Activity 中。我现在遇到的问题是从 mysql 数据库检索列表并显示此列表我已经运行并执行了一个自定义代码，该代码在单个列表中显示从 mysql 数据库检索到的项目列表，效果很好。现在将此代码引入我的程序会出现 3 个错误
1)

pDialog = new ProgressDialog(MealsFragment.this); which says        
ProgressDialog(android.context,Context) in progressDialog cannot be applied to          
com.example.tab.tablayout.MealsFragment

2) runOnUiThread(new Runnable() 表示“无法解析 runonuithread 方法”

3)都是关于列表适配器的。

初始代码使用OnCreate，但我的 fragment 使用oncreateView。我不知道这是否是问题所在。

这是 MealsFragment.java 的代码

package com.example.tabs.tablayout;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;

/**
 * Created by GIGABYTE on 5/21/2014.
 */
public class MealsFragment extends ListFragment {

    // Progress Dialog
    private ProgressDialog pDialog;

    // Creating JSON Parser object
    JSONParser jParser = new JSONParser();

    ArrayList<HashMap<String, String>> mealsList;

    // url to get all products list
    private static String url_all_meals = "http://10.180.79.73/dbase_connect/get_all_meals.php";

    // JSON Node names
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_MEALS = "meals";
    private static final String TAG_MID = "mid";
    private static final String TAG_NAME = "name";

    // products JSONArray
    JSONArray meals = null;

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

        View rootView = inflater.inflate(R.layout.fragment_meals, container, false);



        // Hashmap for ListView
        mealsList = new ArrayList<HashMap<String, String>>();

        // Loading meals in Background Thread
        new LoadAllMeals().execute();


        // Get listview
        ListView lv = getListView();

        return rootView;
    }


    /**
         * Background Async Task to Load all product by making HTTP Request
         * */
       class LoadAllMeals extends AsyncTask<String, String, String> {

            /**
             * Before starting background thread Show Progress Dialog
             * */

            protected void onPreExecute() {
                super.onPreExecute();
                pDialog = new ProgressDialog(MealsFragment.this);
                pDialog.setMessage("Loading Meals. Please wait...");
                pDialog.setIndeterminate(false);
                pDialog.setCancelable(false);
                pDialog.show();
            }

            /**
             * getting All Meals from url
             * */
            protected String doInBackground(String... args) {
                // Building Parameters
                List<NameValuePair> params = new ArrayList<NameValuePair>();
                // getting JSON string from URL
                JSONObject json = jParser.makeHttpRequest(url_all_meals, "GET", params);

                // Check your log cat for JSON response
                Log.d("All Meals: ", json.toString());

                try {
                    // Checking for SUCCESS TAG
                    int success = json.getInt(TAG_SUCCESS);

                    if (success == 1) {
                        // Meals found
                        // Getting Array of Meals
                        meals = json.getJSONArray(TAG_MEALS);

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

                            // Storing each json item in variable
                            String id = c.getString(TAG_MID);
                            String name = c.getString(TAG_NAME);

                            // creating new HashMap
                            HashMap<String, String> map = new HashMap<String, String>();

                            // adding each child node to HashMap key => value
                            map.put(TAG_MID, id);
                            map.put(TAG_NAME, name);

                            // adding HashList to ArrayList
                            mealsList.add(map);
                        }
                    } /*else {
                        // no products found
                        // Launch Add New product Activity
                        Intent i = new Intent(getApplicationContext(),
                                NewProductActivity.class);
                        // Closing all previous activities
                        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        startActivity(i);
                    }
                    */
                } catch (JSONException e) {
                    e.printStackTrace();
                }

                return null;
            }

            /**
             * After completing background task Dismiss the progress dialog
             * **/
            protected void onPostExecute(String file_url) {
                // dismiss the dialog after getting all meals
                pDialog.dismiss();
                // updating UI from Background Thread
                runOnUiThread(new Runnable() {
                    public void run() {
                        /**
                         * Updating parsed JSON data into ListView
                         * */
                        ListAdapter adapter = new SimpleAdapter(
                                MealsFragment.this, mealsList,
                                R.layout.meals_list_item, new String[] {TAG_MID,
                                TAG_NAME},
                                new int[] { R.id.mid, R.id.name });
                        // updating listview
                        setListAdapter(adapter);


                    }
                });

            }


}
}

Answer 1

1) ProgressDialog 构造函数的第一个参数必须是上下文。使用

new ProgressDialog(getActivity());

2) 您可以使用getActivity().runOnUiThread(...)。然而，在这种情况下这不是必需的。 AsyncTask.onPostExecute() 方法已在 UI 线程中运行。只需将 Runnable 代码移至 onPostExecute() 方法的主体中即可。

3) 与1相同，第一个参数必须是上下文。使用new SimpleAdapter(getActivity(), ...)。