java.lang.NullPointerException在Android中向ListView获取数据

时间：2014-04-16 06:56:23

标签： android listview nullpointerexception listadapter

Hie Friends

我有一个ListView，它显示来自JSON解析器的图像数据，因为我使用自定义基本适配器。

但我得到了以下异常。

FATAL EXCEPTION: main
java.lang.NullPointerException
    at com.example.ecard.ECard_main$AsycLove.onPostExecute(ECard_main.java:193)
    at com.example.ecard.ECard_main$AsycLove.onPostExecute(ECard_main.java:1)
    at android.os.AsyncTask.finish(AsyncTask.java:602)
    at android.os.AsyncTask.access$600(AsyncTask.java:156)
    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:4424)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:511)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
    at dalvik.system.NativeStart.main(Native Method)

我的代码是：

package com.example.ecard;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
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.JSONArray;
import org.json.JSONObject;

import com.loopj.android.image.SmartImageView;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.util.Log;
import android.view.View;
import android.view.Window;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class ECard_main extends Activity 
{
    String catagories;
    String anim_id,album_id,anim_name,anim_thumb,anim_url;

    TextView title;
    SmartImageView image;
    ListView hlv;
    ArrayList<HashMap<String, String>> albumList;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ecard_main);

        Intent i=getIntent();
        catagories=i.getExtras().getString("Catagories");


        title=(TextView)findViewById(R.id.tv_main_title);
        image=(SmartImageView)findViewById(R.id.IV_image);
        title.setText(catagories);

        //hlv = getListView();
        hlv = (ListView) findViewById(android.R.id.list);

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

        new AsycLove().execute();

    }

    class AsycLove extends AsyncTask<String, String, String>     
    {
        ProgressDialog progressDialog;      

        @Override
        protected void onPreExecute() 
        {
            super.onPreExecute();            
            progressDialog = new ProgressDialog(ECard_main.this);
            progressDialog.setTitle("Loading");
            progressDialog.setMessage("Please wait");
            progressDialog.setCancelable(false);
            progressDialog.setIndeterminate(true);
            progressDialog.show();
        }

        @Override
        protected String doInBackground(String... aurl)        
        {           
            try 
            {
                HttpPost postMethod = new HttpPost("http://demo1.idevtechnolabs.com/smartecard/love.php");              
                BufferedReader bufferedReader = null;

                HttpClient client = new DefaultHttpClient();
                HttpResponse response = null;

                response = client.execute(postMethod);
                final int statusCode = response.getStatusLine().getStatusCode();

                Log.v("Album ::","Response:::--->"+response.toString());
                Log.v("Album ::","Status Code:::--->"+statusCode);

                bufferedReader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
                StringBuffer stringBuffer = new StringBuffer("");
                String line = "";
                String LineSeparator = System.getProperty("line.separator");
                while ((line = bufferedReader.readLine()) != null) 
                {
                    stringBuffer.append(line + LineSeparator); 
                }
                bufferedReader.close(); 

                //-------------CONVERT DATA TO JSON---------------------------------

                try 
                {
                    String myjsonstring = stringBuffer.toString();

                    JSONArray jsonArray = new JSONArray(myjsonstring);

                    JSONObject jsonObj = null;

                    albumList.clear();

                    jsonObj = jsonArray.getJSONObject(0);   


                    for(int i=0; i<jsonArray.length();i++)
                    {
                            jsonObj = jsonArray.getJSONObject(i);                           

                            anim_id = jsonObj.getString("animation_id");      
                            album_id = jsonObj.getString("album_id");
                            anim_name = jsonObj.getString("animation_name");      
                            anim_thumb= jsonObj.getString("animation_thumb");
                            anim_url = jsonObj.getString("animation_url");    

                            anim_url=anim_url.replaceAll("\"","");


                            Log.v("Anim URL","Anim URL::"+anim_url);
                            Log.v("Anim Name","Anim Name::"+anim_name);

                            HashMap<String, String> tmp_album = new HashMap<String, String>();
                            tmp_album.put("anim_id", anim_id);
                            tmp_album.put("anim_thumb", anim_thumb);
                            albumList.add(tmp_album);   

                    }

                } 
                catch (Exception e) 
                {
                    Log.v("Home ::","Call JSON Exception in get Album in List--->"+e.toString());
                    e.printStackTrace();
                }
            } 
            catch (IOException e) 
            {
                Log.v("Exception: Get get Album in List","Name-"+e.toString());
                e.printStackTrace();
            }

            return "0";
        }

        @Override
        protected void onPostExecute(String code) 
        {   

            Toast.makeText(getApplicationContext(), "Image URL Call Successfully", Toast.LENGTH_LONG).show();
                Log.v("Album","Album List::"+albumList);
            ECard_main_Custom_Adapter adapter =new ECard_main_Custom_Adapter(getApplicationContext(),albumList);
            hlv.setAdapter(adapter);                

            progressDialog.dismiss();
            progressDialog = null;

        }
    }

}

我的适配器是：

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

import com.loopj.android.image.SmartImageView;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

public class ECard_main_Custom_Adapter extends BaseAdapter
{
    private Context context;
    ArrayList<HashMap<String, String>> listAlbum;

    ViewHolder vholder;
    Drawable image; 

    public ECard_main_Custom_Adapter(Context context, ArrayList<HashMap<String, String>> albumList) 
    {

        this.context = context;
        this.listAlbum=albumList;
    }

    @Override
    public int getCount() 
    {
        Log.v("1","1");
        return listAlbum.size();
    }

    @Override
    public Object getItem(int position) 
    {
        Log.v("1","2");
        return position;
    }

    @Override
    public long getItemId(int position) 
    {
        Log.v("1","3");
        return 0;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) 
    {
        Log.v("1","1");
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);   
        View vi=convertView;


        vi = inflater.inflate(R.layout.ecard_main_adapter, null);

        vholder = new ViewHolder();
        vholder.img_album=(SmartImageView)vi.findViewById(R.id.IV_image);
        vi.setTag(vholder);

        try
        {
            String anim_id=listAlbum.get(position).get("anim_id");
            String url=listAlbum.get(position).get("anim_thumb");

            Log.v("Anim ID and Anim URL","Id:"+anim_id+" URL:"+url);

            vholder.img_album.setImageUrl(url);
        }
        catch (Exception e) 
        {
            // TODO: handle exception
            Log.v("Error Ecard","Error is:::"+e);
        }
        return vi;
    } 

    static class ViewHolder 
    {
        SmartImageView img_album;
    }
}

请告诉我错在哪里。

感谢任何帮助。

提前致谢。

1 个答案:

答案 0 :(得分：8)

首先纠正这个

 hlv = (ListView) findViewById(android.R.id.list);

到

 hlv = (ListView) findViewById(R.id.list);

可能会导致错误。并确保您的ecard_main.xml布局包含ListView，其ID为list

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