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サーバーにリクエストしてリストを取得しようとしています。そのために、asynctask を使用して対処しています。コードは次のようになります。オンラインで非常に多くの実験を行った後でも、次のように logcat エラーが発生します。

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

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

import android.app.AlarmManager;
import android.app.ListActivity;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;

public class AndroidJSONParsingActivity extends ListActivity {

public static String url = "http://ensignweb.com/sandbox/app/comment11.php";

    // JSON Node names
    protected static final String TAG_PRODUCTS = "products";
    protected static final String TAG_CID = "cid";
    public static final String TAG_NAME = "name";

    // contacts JSONArray
    JSONArray products = null;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        new Message().execute(url);
        startService(new Intent(this, UpdateService.class));
        Intent intent = new Intent(this,UpdateService.class);
        PendingIntent pIntent = PendingIntent.getService(this, 0, intent, 0);
        AlarmManager alarm = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        alarm.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 30000, pIntent);


    }

@Override
    protected void onStart() {
        // TODO Auto-generated method stub
        super.onStart();

    }
    //Belongs to update service
    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
//      stopService(new Intent(this, UpdateService.class));
    }

    class Message extends AsyncTask<String, Integer, ArrayList<HashMap<String, String>> > {
        ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

                @Override
            protected ArrayList<HashMap<String, String>> doInBackground(String... params) {

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

                    // getting JSON string from URL
                    JSONObject json = jParser.getJSONFromUrl(params[0]);


                    try {
                        // Getting Array of Contacts
                        products = json.getJSONArray(TAG_PRODUCTS);

                        // looping through All Contacts
                        for(int i = products.length()-1; i >=0; i--){
                            JSONObject c = products.getJSONObject(i);

                            // Storing each json item in variable
                            String cid = c.getString(TAG_CID);
                            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_CID, cid);
                            map.put(TAG_NAME, name);

                            // adding HashList to ArrayList
                            mylist.add(map);
                            Log.d("value", mylist.toString());
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                    return mylist;
                }

            @Override
            protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
                ListAdapter adapter = new SimpleAdapter(AndroidJSONParsingActivity.this, result , R.layout.list_item,new String[] { TAG_NAME,}, new int[] {
                        R.id.name});
                AndroidJSONParsingActivity.this.setListAdapter(adapter);// If Activity extends ListActivity
                final ListView lv = getListView();
                lv.setTextFilterEnabled(true);

            }

    }
}

JSONParser.java

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

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
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 JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    public JSONObject getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();           

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        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();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

logcat はこのメッセージを表示します

    01-11 11:46:34.331: E/Buffer Error(483): Error converting result java.io.IOException: Attempted read on closed stream.
01-11 11:46:34.331: E/JSON Parser(483): Error parsing data org.json.JSONException: End of input at character 0 of 
01-11 11:46:34.331: W/dalvikvm(483): threadid=7: thread exiting with uncaught exception (group=0x4001d800)
01-11 11:46:34.342: E/AndroidRuntime(483): FATAL EXCEPTION: AsyncTask #1
01-11 11:46:34.342: E/AndroidRuntime(483): java.lang.RuntimeException: An error occured while executing doInBackground()
01-11 11:46:34.342: E/AndroidRuntime(483):  at android.os.AsyncTask$3.done(AsyncTask.java:200)
01-11 11:46:34.342: E/AndroidRuntime(483):  at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
01-11 11:46:34.342: E/AndroidRuntime(483):  at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
01-11 11:46:34.342: E/AndroidRuntime(483):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
01-11 11:46:34.342: E/AndroidRuntime(483):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
01-11 11:46:34.342: E/AndroidRuntime(483):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
01-11 11:46:34.342: E/AndroidRuntime(483):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
01-11 11:46:34.342: E/AndroidRuntime(483):  at java.lang.Thread.run(Thread.java:1096)
01-11 11:46:34.342: E/AndroidRuntime(483): Caused by: java.lang.NullPointerException
01-11 11:46:34.342: E/AndroidRuntime(483):  at com.androidhive.jsonparsing.AndroidJSONParsingActivity$Message.doInBackground(AndroidJSONParsingActivity.java:95)
01-11 11:46:34.342: E/AndroidRuntime(483):  at com.androidhive.jsonparsing.AndroidJSONParsingActivity$Message.doInBackground(AndroidJSONParsingActivity.java:1)
01-11 11:46:34.342: E/AndroidRuntime(483):  at android.os.AsyncTask$2.call(AsyncTask.java:185)
01-11 11:46:34.342: E/AndroidRuntime(483):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
01-11 11:46:34.342: E/AndroidRuntime(483):  ... 4 more

log.d "json string" は次のように表示されます

01-11 12:43:29.891: D/json string(629): {"success":1,"products":[{"cid":"1","name":"bernard"},{"cid":"2","name":"Vijay"},{"cid":"3","name":"vikas_admin"},{"cid":"4","name":"vikas_admin"},{"cid":"5","name":"vikas_admin"},{"cid":"6","name":"vikas_admin"},{"cid":"7","name":"Vikas B L"},{"cid":"8","name":"chanakyavikas"},{"cid":"9","name":"vikram"},{"cid":"10","name":"Vidya"},{"cid":"11","name":"bernard"},{"cid":"12","name":"Thenewone"},{"cid":"13","name":"another"},{"cid":"14","name":"1245"},{"cid":"15","name":"kljdf.d,samfas"},{"cid":"16","name":"this"},{"cid":"17","name":"l;asdkfjalskjf"},{"cid":"18","name":"just got refreshed "},{"cid":"19","name":"not working"},{"cid":"20","name":"Checking"},{"cid":"21","name":"trying again"},{"cid":"22","name":"checking after few minutes"},{"cid":"23","name":"checking after many minutes"},{"cid":"24","name":"this one after 40 mintues"},{"cid":"25","name":"Let me try it once again. Even after this, it must run"},{"cid":"26","name":"Coming to track"},{"cid":"27","name":"let me check after 40 minutes"},{"cid":"28","name":"Ok. Let me give some time"},{"cid":"29","name":"let me check after lunch"},{"cid":"30","name":"checking after more than 2 hours"},{"cid":"31","name":"Now trying without icon. Lets see how it will gonna work"},{"cid":"32","name":"mic checking"},{"cid":"33","name":"check check check"},{"cid":"34","name":"check check again"},{"cid":"35","name":"Back to work"},{"cid":"36","name":"trying long long long time after"},{"cid":"37","name":"bye byeeeeeeeeeee"},{"cid":"38","name":"how is it going"},{"cid":"39","name":"Good morning Ensign"},{"cid":"40","name":"Trying AlarmManager"},{"cid":"41","name":"alarm! alarm! alarm!"},{"cid":"42","name":"Its been more than 30minutes"},{"cid":"43","name":"Let me see in the mobile about its working"},{"cid":"44","name":"How is it going"},{"cid":"45","name":"How is it going after many hours"},{"cid":"46","name":"huga huga huga"},{"cid":"47","name":"bye bye"},{"cid":"48","name":"It is now 7.47"},{"cid":"49","name":"Good morning Ensign"},{"cid":"50","name":"Once again good morning"},{"cid":"51","name":"Inside the office"},{"cid":"52","name":"Not working again"},{"cid":"53","name":"asdlkfjalsjfdl"},{"cid":"54","name":"Trying again and again"},{"cid":"55","name":"akl;sdjf;las"},{"cid":"56","name":"alarm! alarm! alarm!"},{"cid":"57","name":"adding boot complete"},{"cid":"58","name":"We are three now"},{"cid":"59","name":"check check again again"},{"cid":"60","name":"How is working now"},{"cid":"61","name":"Date is 10\/01\/2013"},{"cid":"62","name":"Now working fine"},{"cid":"63","name":"Had a good lunch"},{"cid":"64","name":"I'm with Mr. Johan "},{"cid":"65","name":"Let me check if booting works or not."},{"cid":"66","name":"checking after rebooting"},{"cid":"67","name":"Nop! rebooting not working"}]}
4

3 に答える 3

1

使用する

 dialog=ProgressDialog.show(AndroidJSONParsingActivity.this, 
                                      "Processing", "Please be patient");

それ以外の

dialog.show(getApplicationContext(), "Processing", "Please be patient");

から表示ProgressDialogするAsyncTask

于 2013-01-10T10:31:12.813 に答える
0

アラートを表示するメソッドでthisinsteadOfgetApplicationContextを使用するonPreExecute

于 2013-01-10T10:33:59.937 に答える
0

スタック トレースは、閉じられたストリームからデータを読み込もうとしていると示しています。これは、ストリームを閉じた後で Web からの応答を読み取ろうとしているように思えます。Web から Json を読み取るときは、これを再確認してください。

また、ヌルポインターを取得しています。これらを見つけるには、デバッガーでコードを 1 行ずつ調べる必要があります (for ループの場合は条件付きブレークポイントを使用します。そうしないとデバッグが困難になります)。一見すると、あなたを殺しているのは次の行だと思います

products = json.getJSONArray(TAG_PRODUCTS);

データがネットから返されなかった場合、json オブジェクトが null になるため、これを推測しています。

これが役立つことを願っています

于 2013-01-11T07:43:48.943 に答える