我想从网址中获取数据和图片，并希望解码并添加到列表视图中。但我发现了一个意外的例外。请解决问题。
public class FoodView extends ListActivity {
private ProgressDialog pDialog;
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList;
private String[] sImage;
private static String url_for_list = "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;
ListView list;
LazyImageLoadAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.food_view);
new LoadAllProducts().execute();
ListView lv = getListView();
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
/* String pid = ((TextView) view.findViewById(R.id.pid)).getText().toString();
String pname = ((TextView) view.findViewById(R.id.name)).getText().toString();
toast(pid + pname);
// Starting new intent
Intent in = new Intent(getApplicationContext(),EditProductActivity.class);
// sending pid to next activity
in.putExtra(TAG_PID, pid);
// starting new activity and expecting some response back
startActivityForResult(in, 100);
*/
}
});
}
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == 100)
{
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
class LoadAllProducts extends AsyncTask<String, String, String>
{
@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();
}
protected String doInBackground(String... args)
{
List<NameValuePair> params = new ArrayList<NameValuePair>();
JSONObject json = jParser.makeHttpRequest(url_for_list, "GET", params);
Log.d("Getting all the list : ", json.toString());
try
{
int success = json.getInt(TAG_SUCCESS);
if(success==1)
{
Log.d("Message : ","Im in if");
products = json.getJSONArray(TAG_PRODUCTS);
sImage = new String[products.length()];
for (int i = 0; i < products.length(); i++)
{
Log.d("Message : ","Im in If For");
JSONObject c = products.getJSONObject(i);
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
String price = c.getString(TAG_PRICE);
String destination = c.getString(TAG_DESTINATION);
String imgname = c.getString(TAG_IMAGE);
sImage[i] = c.getString(TAG_IMAGE);
Log.d("Message : ",sImage[i]);
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_PID, id);
map.put(TAG_NAME, name);
map.put(TAG_DESTINATION, destination);
map.put(TAG_PRICE, price);
map.put(TAG_IMAGE, imgname);
productsList.add(map);
Log.d("Message : ", "Adding in map");
}
}
else
{
}
}catch(JSONException j)
{
j.printStackTrace();
}
return null;
}
protected void postExecute()
{
pDialog.dismiss();
runOnUiThread(new Runnable()
{
public void run()
{
Log.d("Message : ", "Im in post Execute");
list=(ListView)findViewById(R.id.list1);
adapter=new LazyImageLoadAdapter(FoodView.this, sImage,productsList);
list.setAdapter(adapter);
}
});
}
}
@Override
public void onDestroy()
{
list.setAdapter(null);
super.onDestroy();
}
public OnClickListener listener=new OnClickListener()
{
@Override
public void onClick(View arg0)
{
adapter.imageLoader.clearCache();
adapter.notifyDataSetChanged();
}
};
public void onItemClick(int mPosition)
{
String tempValues = sImage[mPosition];
Toast.makeText(FoodView.this,"Image URL : "+tempValues, Toast.LENGTH_LONG).show();
}
}
Logcat错误
04-25 06:14:29.418: D/Message :(3010): Im in if
04-25 06:14:29.428: D/Message :(3010): Im in If For
04-25 06:14:29.428: D/Message :(3010): http://ambrogroup.com/assets/brands/foods/comingsoon.png
04-25 06:14:29.428: W/dalvikvm(3010): threadid=11: thread exiting with uncaught exception (group=0xb4a26ba8)
04-25 06:14:29.468: I/Choreographer(3010): Skipped 38 frames! The application may be doing too much work on its main thread.
04-25 06:14:29.818: I/Choreographer(3010): Skipped 30 frames! The application may be doing too much work on its main thread.
04-25 06:14:30.168: E/AndroidRuntime(3010): FATAL EXCEPTION: AsyncTask #1
04-25 06:14:30.168: E/AndroidRuntime(3010): Process: com.ambrogroup, PID: 3010
04-25 06:14:30.168: E/AndroidRuntime(3010): java.lang.RuntimeException: An error occured while executing doInBackground()
04-25 06:14:30.168: E/AndroidRuntime(3010): at android.os.AsyncTask$3.done(AsyncTask.java:300)
04-25 06:14:30.168: E/AndroidRuntime(3010): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
04-25 06:14:30.168: E/AndroidRuntime(3010): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
04-25 06:14:30.168: E/AndroidRuntime(3010): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
04-25 06:14:30.168: E/AndroidRuntime(3010): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
04-25 06:14:30.168: E/AndroidRuntime(3010): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
04-25 06:14:30.168: E/AndroidRuntime(3010): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
04-25 06:14:30.168: E/AndroidRuntime(3010): at java.lang.Thread.run(Thread.java:841)
04-25 06:14:30.168: E/AndroidRuntime(3010): Caused by: java.lang.NullPointerException
04-25 06:14:30.168: E/AndroidRuntime(3010): at com.ambrogroup.FoodView$LoadAllProducts.doInBackground(FoodView.java:138)
04-25 06:14:30.168: E/AndroidRuntime(3010): at com.ambrogroup.FoodView$LoadAllProducts.doInBackground(FoodView.java:1)
04-25 06:14:30.168: E/AndroidRuntime(3010): at android.os.AsyncTask$2.call(AsyncTask.java:288)
04-25 06:14:30.168: E/AndroidRuntime(3010): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
04-25 06:14:30.168: E/AndroidRuntime(3010): ... 4 more
以下是XML代码food_view.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<!-- Main ListView
Always give id value as list(@android:id/list)
-->
<ListView
android:id="@+id/list1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@drawable/background"
/>
<ListView android:id="@id/android:list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawSelectorOnTop="false"
android:visibility="gone" />
</LinearLayout>
答案 0 :(得分：0)
试试这个。
您尚未初始化 productsList ArrayList。在doInBackground
productsList = ArrayList<HashMap<String, String>>();