Iam在后台通过图像解码从url加载Listview中的图像，但是出现以下错误。
package com.abc;
import java.io.InputStream;
import java.net.URL;
import java.sql.Array;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.R.integer;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.Drawable;
import android.media.Image;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class FoodView extends ListActivity
{
private ProgressDialog pDialog;
private String[] mStrings;
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList;
private static String url_all_products = "http://ambrogroup.com/app/index/file/food";
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "products";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
private static final String TAG_IMAGE = "img";
private static final String TAG_DESTINATION = "destination";
private static final String TAG_PRICE = "price";
JSONArray products = null;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.food_view);
// productsList = new ArrayList<HashMap<String, String>>(); // Hashmap for ListView
new LoadAllProducts().execute(); // Loading products in Background Thread by explicit function
ListView listview = getListView(); // Get listview
listview.setOnItemClickListener(new OnItemClickListener() { // on seleting single product // launching Edit Product Screen
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
//getting values from selected ListItem
String pid = ((TextView) view.findViewById(R.id.pid)).getText().toString();
String pname = ((TextView) view.findViewById(R.id.name)).getText().toString();
String pimg = ((TextView) view.findViewById(R.id.img)).getText().toString();
String pdestination = ((TextView) view.findViewById(R.id.destination)).getText().toString();
String pprice = ((TextView) view.findViewById(R.id.price)).getText().toString();
}
});
}
class LoadAllProducts extends AsyncTask<String, String, String>
{
ListView listView;
ArrayList<ItemList> listArray = new ArrayList<ItemList>();
CustomListViewAdapter customGridAdapter;
@Override
protected void onPreExecute()
{
super.onPreExecute();
pDialog = new ProgressDialog(FoodView.this);
pDialog.setMessage("Loading list. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);
// Check your log cat for JSON reponse
Log.d("Getting all the list : ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1)
{
products = json.getJSONArray(TAG_PRODUCTS);
for (int i = 0; i < products.length(); i++)
{
JSONObject c = products.getJSONObject(i);
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
String img = c.getString(TAG_IMAGE);
String destination = c.getString(TAG_DESTINATION);
String price = c.getString(TAG_PRICE);
mStrings[i] = img;
String urldisplay = mStrings[i];
Bitmap mIcon11 = null;
try {
InputStream in = new java.net.URL(urldisplay).openStream();
mIcon11 = BitmapFactory.decodeStream(in);
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
listArray.add(new ItemList(mIcon11,id,name,destination,price));
listView = (ListView) findViewById(R.id.list_item);
customGridAdapter = new CustomListViewAdapter(FoodView.this, R.layout.row_grid, listArray);
listView.setAdapter(customGridAdapter);
}
}
else
{
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
}
}
获得以下错误
04-23 05:15:15.839: E/AndroidRuntime(1398): FATAL EXCEPTION: AsyncTask #1
04-23 05:15:15.839: E/AndroidRuntime(1398): Process: com.ambrogroup, PID: 1398
04-23 05:15:15.839: E/AndroidRuntime(1398): java.lang.RuntimeException: An error occured while executing doInBackground()
04-23 05:15:15.839: E/AndroidRuntime(1398): at android.os.AsyncTask$3.done(AsyncTask.java:300)
04-23 05:15:15.839: E/AndroidRuntime(1398): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
04-23 05:15:15.839: E/AndroidRuntime(1398): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
04-23 05:15:15.839: E/AndroidRuntime(1398): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
04-23 05:15:15.839: E/AndroidRuntime(1398): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
04-23 05:15:15.839: E/AndroidRuntime(1398): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
04-23 05:15:15.839: E/AndroidRuntime(1398): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
04-23 05:15:15.839: E/AndroidRuntime(1398): at java.lang.Thread.run(Thread.java:841)
04-23 05:15:15.839: E/AndroidRuntime(1398): Caused by: java.lang.NullPointerException
04-23 05:15:15.839: E/AndroidRuntime(1398): at com.ambrogroup.FoodView$LoadAllProducts.doInBackground(FoodView.java:129)
04-23 05:15:15.839: E/AndroidRuntime(1398): at com.ambrogroup.FoodView$LoadAllProducts.doInBackground(FoodView.java:1)
04-23 05:15:15.839: E/AndroidRuntime(1398): at android.os.AsyncTask$2.call(AsyncTask.java:288)
04-23 05:15:15.839: E/AndroidRuntime(1398): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
04-23 05:15:15.839: E/AndroidRuntime(1398): ... 4 more
04-23 05:15:15.899: I/Choreographer(1398): Skipped 43 frames! The application may be doing too much work on its main thread.
04-23 05:15:16.339: I/Choreographer(1398): Skipped 196 frames! The application may be doing too much work on its main thread.
04-23 05:15:16.659: I/Choreographer(1398): Skipped 206 frames! The application may be doing too much work on its main thread.
04-23 05:15:17.009: I/Choreographer(1398): Skipped 222 frames! The application may be doing too much work on its main thread.
04-23 05:15:17.819: I/Choreographer(1398): Skipped 527 frames! The application may be doing too much work on its main thread.
04-23 05:15:18.139: I/Choreographer(1398): Skipped 124 frames! The application may be doing too much work on its main thread.
04-23 05:15:18.769: E/WindowManager(1398): android.view.WindowLeaked: Activity com.ambrogroup.FoodView has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{b50b0648 V.E..... R.....ID 0,0-304,96} that was originally added here
04-23 05:15:18.769: E/WindowManager(1398): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:348)
04-23 05:15:18.769: E/WindowManager(1398): at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:248)
04-23 05:15:18.769: E/WindowManager(1398): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
04-23 05:15:18.769: E/WindowManager(1398): at android.app.Dialog.show(Dialog.java:286)
04-23 05:15:18.769: E/WindowManager(1398): at com.ambrogroup.FoodView$LoadAllProducts.onPreExecute(FoodView.java:98)
04-23 05:15:18.769: E/WindowManager(1398): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
04-23 05:15:18.769: E/WindowManager(1398): at android.os.AsyncTask.execute(AsyncTask.java:535)
04-23 05:15:18.769: E/WindowManager(1398): at com.ambrogroup.FoodView.onCreate(FoodView.java:63)
04-23 05:15:18.769: E/WindowManager(1398): at android.app.Activity.performCreate(Activity.java:5231)
04-23 05:15:18.769: E/WindowManager(1398): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-23 05:15:18.769: E/WindowManager(1398): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-23 05:15:18.769: E/WindowManager(1398): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-23 05:15:18.769: E/WindowManager(1398): at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-23 05:15:18.769: E/WindowManager(1398): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-23 05:15:18.769: E/WindowManager(1398): at android.os.Handler.dispatchMessage(Handler.java:102)
04-23 05:15:18.769: E/WindowManager(1398): at android.os.Looper.loop(Looper.java:136)
04-23 05:15:18.769: E/WindowManager(1398): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-23 05:15:18.769: E/WindowManager(1398): at java.lang.reflect.Method.invokeNative(Native Method)
04-23 05:15:18.769: E/WindowManager(1398): at java.lang.reflect.Method.invoke(Method.java:515)
04-23 05:15:18.769: E/WindowManager(1398): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-23 05:15:18.769: E/WindowManager(1398): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-23 05:15:18.769: E/WindowManager(1398): at dalvik.system.NativeStart.main(Native Method)
04-23 05:15:18.769: I/Choreographer(1398): Skipped 96 frames! The application may be doing too much work on its main thread.
04-23 05:15:18.849: I/Choreographer(1398): Skipped 46 frames! The application may be doing too much work on its main thread.
04-23 05:15:20.819: I/Process(1398): Sending signal. PID: 1398 SIG: 9
答案 0 :(得分：0)
按照原因：
java.lang.NullPointerException in
04-23 05:15:15.839: E/AndroidRuntime(1398): at com.ambrogroup.FoodView$LoadAllProducts.doInBackground(FoodView.java:129)
调试你的代码并尝试打印响应json，它可能是null，你试图访问它。
PS如果实际行号与您的代码段相同，我注意到
FoodView.java:129有空 你在哪里访问
mStrings[i] = img;
并且尚未初始化mStrings数组，需要添加行
String[] mStrings= new String[products.length()];
，然后将值赋给mStrings数组
欢呼声