Question

我正在研究一个机器人应用程序。它必须从基于 Json 的互联网上读到一些信息。我已经想通了。但是当我测试我的应用程序时, 应用程序会卡在它下载种子的部分。用户界面会被卡在几秒钟内。

我已虚构出我需要利用 AsyncTassk 类在和机器人上运行背景连接。我读了这么多关于这个主题的书, 几乎可以做这个理论的梦。现在,在实践上,这让我有点问题。

该应用程序现在有一堆课程, 但处理种子下载并将重数据放入列表的分类( 活动) 。该类名为 KVO - NWS 的荷兰语 :

package com.appsoweb.kvodeventer;

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

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

import com.appsoweb.kvodeventer.JSONfunctions;
import com.appsoweb.kvodeventer.KVONieuws;
import com.appsoweb.kvodeventer.R;

import android.app.ListActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;

public class KVONieuws extends ListActivity {
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.listplaceholder);

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

        JSONObject json = JSONfunctions.getJSONfromURL("http://crossalertdeventer.nl/api/news.json");

        try{

            JSONArray  earthquakes = json.getJSONArray("items");

            for(int i=0;i<earthquakes.length();i++){                        
                HashMap<String, String> map = new HashMap<String, String>();    
                JSONObject e = earthquakes.getJSONObject(i);

                map.put("id",  String.valueOf(i));
                map.put("name", "Titel:" + e.getString("title"));
                map.put("image", "Image: " +  e.getString("image"));
                mylist.add(map);            
            }       
        }catch(JSONException e)        {
             Log.e("log_tag", "Parsing error "+e.toString());
        }


        ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.singlelistitem, 
                        new String[] { "name", "image" }, 
                        new int[] { R.id.item_title, R.id.item_subtitle });

        setListAdapter(adapter);

        final ListView lv = getListView();
        lv.setTextFilterEnabled(true);  
        lv.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {              
                @SuppressWarnings("unchecked")
                HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position);                   
                Toast.makeText(KVONieuws.this, "ID  " + o.get("id") + "  was clicked.", Toast.LENGTH_SHORT).show(); 

            }
        });
    }
}

现在,我又创造了另一个班叫做JSONFORTS. JAVA在这里处理JSON部分的故事:

package com.appsoweb.kvodeventer;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONfunctions {

    public static JSONObject getJSONfromURL(String url){
        InputStream is = null;
        String result = "";
        JSONObject jArray = null;

        //http post
        try{
                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost(url);
                httppost.setHeader("User-Agent", "9fb01091b51527555d1d3fc87709918f");
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity entity = response.getEntity();
                is = entity.getContent();

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

      //convert response to string
        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 + "
");
                }
                is.close();
                result=sb.toString();
        }catch(Exception e){
                Log.e("log_tag", "Error converting result "+e.toString());
        }

        try{

            jArray = new JSONObject(result);            
        }catch(JSONException e){
                Log.e("log_tag", "Error parsing data "+e.toString());
        }

        return jArray;
    }
}

现在我用这个代码做了很多尝试使(重的部分)在背景上作为线条运行, 我理解它的理论, 我只是不能让它工作。我不知道为什么...

有没有人可以简单地调整我的代码或给指示器在哪里执行一个内部阶级也许可以扩展AsyncTashsk类, 并给出一个想法如何把什么代码在运行在背景方法和背出...

感谢任何能帮我的人!

Answer 1

调用 new MyRssReadTask (. execute (); 在 Create 方法上 ...

  class MyRssReadTask extends AsyncTask<Void, Void, JSONObject> {
        ProgressDialog waitingDialog;
        @Override
        protected void onPreExecute() {
            waitingDialog = new ProgressDialog(KVONieuws.this);
            waitingDialog.setMessage("Loading...");
            waitingDialog.show();
            super.onPreExecute();
        }

        @Override
        protected Void doInBackground(Void... unused) {

           JSONObject json = JSONfunctions.getJSONfromURL("http://crossalertdeventer.nl/api/news.json");

            return json;
        }

        @Override
        protected void onPostExecute(JSONObject objJson) {
            super.onPostExecute(result);
            if(waitingDialog.isshowing()){  
            waitingDialog.dismiss();}

           //do stuff here 
            JSONArray  earthquakes = objJson.getJSONArray("items");
        }
    }

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