Question

我已经解析了JSON解析收到的数据。现在我想使用arrayadapter在listview中显示已解析的数据。但应用程序崩溃。当我删除JP类的功能，即片段活动中的parseJSON和getJSON，应用程序运行但列表视图中没有任何内容.pls帮助代码： JP.class

package secondslash.secondslash;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.Base64;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;


/**
 * Created by alokit nigam on 12/5/2015.
 */
public class JP extends Activity {

    String JSON_STRING,json_string;
    public Bitmap bmp;

    CustomListViewAdapter customListViewAdapter;
    public void getJSON(){
        new BackgroundTask1().execute();
    }
    public void parseJSON(){
        try {
            JSONObject jsonObject=new JSONObject(json_string);
            JSONArray jsonArray=jsonObject.getJSONArray("server_response");
            int count=0;
            String articleId,topicId,headline,article,image;

            while(count<jsonArray.length()){

                JSONObject JO=jsonArray.getJSONObject(count);
                articleId=JO.getString("article_id");
                topicId=JO.getString("topic_id");
                headline=JO.getString("headline");
                article=JO.getString("article");
                image=JO.getString("image");
                byte[] qrimage = Base64.decode(image.getBytes(), count);
                bmp = BitmapFactory.decodeByteArray(qrimage, 0, qrimage.length);
                newsDetails nd=new newsDetails(articleId,topicId,headline,article,bmp);
                customListViewAdapter.add(nd);
                count++;

            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }



    class BackgroundTask1 extends AsyncTask<Void,Void,String>
    {
        String json_url;
        @Override
        protected void onPreExecute() {
            json_url="http://secondslash.site88.net/json_get_data.php";

        }

        @Override
        protected String doInBackground(Void... params) {

            try {
                URL url=new URL(json_url);
                HttpURLConnection httpURLConnection=(HttpURLConnection)url.openConnection();
                InputStream inputStream=httpURLConnection.getInputStream();
                BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(inputStream));
                StringBuilder stringBuilder=new StringBuilder();
                while ((JSON_STRING=bufferedReader.readLine())!=null){
                    stringBuilder.append(JSON_STRING+"\n");
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();

                return stringBuilder.toString().trim();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
        }

        @Override
        protected void onPostExecute(String result) {

            json_string=result;
        }
    }



}

CustomAdapter.java

package secondslash.secondslash;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

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

import secondslash.secondslash.mainActivity.topnewsFragment;

public class CustomListViewAdapter extends ArrayAdapter {

    List list=new ArrayList();

    public CustomListViewAdapter(Context context, int resource) {
        super(context, resource);
    }


    public void add(newsDetails object) {
        super.add(object);
        list.add(object);
    }

    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View row;
        row=convertView;
        ContactHolder contactHolder;
        if(row==null){
            LayoutInflater layoutInflater=(LayoutInflater)this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row=layoutInflater.inflate(R.layout.list_news,parent,false);
            contactHolder=new ContactHolder();
            contactHolder.title=(TextView)row.findViewById(R.id.title);
            contactHolder.desc=(TextView)row.findViewById(R.id.desc);
            contactHolder.icon=(ImageView)row.findViewById(R.id.icon);
            row.setTag(contactHolder);
        }
        else {
            contactHolder=(ContactHolder)row.getTag();
        }

        newsDetails contacts=(newsDetails)this.getItem(position);
        contactHolder.title.setText(contacts.getheadline());
        contactHolder.desc.setText(contacts.gettopicId());
        contactHolder.icon.setImageBitmap(contacts.getImage());

        return row;
    }

    static class ContactHolder{
        TextView title,desc;
        ImageView icon;
    }
}

newsDetails.java

package secondslash.secondslash;

import android.graphics.Bitmap;
import android.media.Image;
import android.widget.ImageView;

/**
 * Created by alokit nigam on 12/3/2015.
 */
public class newsDetails {
    private String articleId,topic_id,headline,article;
    Bitmap image;



        public newsDetails(String articleId,String topic_id,String headline,String article,Bitmap image){
            this.setarticleId(articleId);
            this.settopicId(topic_id);
            this.setheadline(headline);
            this.setArticle(article);
            this.setImage(image);
        }

        public String getarticleId() {
            return articleId;
        }

        public void setarticleId(String articleId) {
            this.articleId = articleId;
        }

        public String gettopicId() {
            return topic_id;
        }

        public void settopicId(String topic_id) {
            this.topic_id = topic_id;
        }

        public String getheadline() {
            return headline;
        }

        public void setheadline(String headline) {
            this.headline = headline;
        }
    public String getArticle() {
        return article;
    }

    public void setArticle(String article) {
        this.article = article;
    }
    public Bitmap getImage(){
        return image;
    }
    public void setImage(Bitmap image){
        this.image=image;
    }
    }

topnews.java

package secondslash.secondslash.mainActivity;

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Toast;

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

import secondslash.secondslash.Adapter;
import secondslash.secondslash.CustomListViewAdapter;
import secondslash.secondslash.JP;
import secondslash.secondslash.R;
import secondslash.secondslash.RowItem;
import secondslash.secondslash.feedsActivity;

/**
 * Created by alokit nigam on 7/29/2015.
 */
public class topnewsFragment extends Fragment {

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.topnews_layout, null);


        ListView list = (ListView) view.findViewById(R.id.list);
        CustomListViewAdapter cus = new CustomListViewAdapter(getContext(), R.layout.list_news);
        list.setAdapter(cus);
        JP jp = new JP();
        jp.getJSON();
        jp.parseJSON();


        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int pos,
                                    long arg3) {
                // TODO Auto-generated method stub
                Toast.makeText(getContext(), "You clicked on position : " + pos + " and id : " + arg3, Toast.LENGTH_LONG).show();

                Intent myIntent = new Intent(getContext(), feedsActivity.class);
                startActivity(myIntent);
            }

        });

        return view;

    }
}

Answer 1

解析必须在执行后的AsyncTask中完成。 AsyncTask（获取JSON数据）在后台线程中完成。同时，你的主线程继续你的getJson方法，你希望son_string对象从你的JSON请求中收到所有信息，但这可能还没有完成

使用arrayadapter在片段的列表视图中显示已解析的数据

1 个答案: