java - Android ProgressDialog 显示何时检索数据

Question

我创建了一个进程来执行从服务器读取json数据的过程。读取数据后，我希望在页面读取数据时出现 ProgressDialog，并在所有数据显示到 ListView 时消失。

我已经制作并放置了:

ProgressDialog progress = new ProgressDialog(this);
progress.setMessage("Wait while loading...");
progress.show();

但总是失败。

对于本例，所有数据已成功正确显示在 ListView 中，我只想使用 ProgressDialog 来帮助显示数据检索过程。

我的 Activity :

package com.joris.moviesmonitoring;

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

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import com.joris.moviesmonitoring.JSONParser;

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.View;
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;

public class MainActivity extends ListActivity {

        // url to make request
        private static String url = "http://api.mydomain.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_PHONE = "phone";
        private static final String TAG_PHONE_MOBILE = "mobile";

        // contacts JSONArray
        JSONArray contacts = null;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
            .permitAll().build();
            StrictMode.setThreadPolicy(policy);


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

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

            // getting JSON string from URL
            JSONObject json = jParser.getJSONFromUrl(url);


            try {
                // Getting Array of Contacts
                contacts = json.getJSONArray(TAG_CONTACTS);

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

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

                    // Phone number is agin JSON Object
                    JSONObject phone = c.getJSONObject(TAG_PHONE);
                    String mobile = phone.getString(TAG_PHONE_MOBILE);

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

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

                    // adding HashList to ArrayList
                    contactList.add(map);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }



            /**
             * Updating parsed JSON data into ListView
             * */
            ListAdapter adapter = new SimpleAdapter(this, contactList,
                    R.layout.list_item,
                    new String[] { 
                        TAG_NAME, 
                        TAG_EMAIL, 
                        TAG_PHONE_MOBILE,
                        TAG_PHONE_MOBILE
                    }, new int[] {
                            R.id.name, 
                            R.id.email, 
                            R.id.mobile,
                            R.id.desc
                    });

            setListAdapter(adapter);


            // selecting single ListView item
            ListView lv = getListView();

            // Launching new screen on Selecting Single ListItem
            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 new intent
                    Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
                    in.putExtra(TAG_NAME, name);
                    in.putExtra(TAG_EMAIL, cost);
                    in.putExtra(TAG_PHONE_MOBILE, description);
                    startActivity(in);

                }
            });



        }



}

我尝试过:progressDialog in AsyncTask但结果总是失败。我对java很陌生。

Answer 1

它可能没有出现，因为数据在对话框有时间创建之前就完成了，所以您在对话框出现之前就取消了对话框。要测试这一点，请在处理完成后不要取消对话框，然后放开它。如果出现对话框，那就是你的问题了