我被困在这个堆栈跟踪上，我不知道它背后的原因是什么。
06-27 17:05:14.841: W/SingleClientConnManager(1519): Invalid use of SingleClientConnManager: connection still allocated.
06-27 17:05:14.841: W/SingleClientConnManager(1519): Make sure to release the connection before allocating another one.
06-27 17:05:15.031: E/log_tag(1519): Error in http connection java.net.SocketException: Socket closed
06-27 17:05:15.077: E/log_tag(1519): Error converting result java.lang.NullPointerException
06-27 17:05:15.181: E/log_tag(1519): Error parsing data org.json.JSONException: End of input at character 0 of
06-27 17:05:15.531: W/dalvikvm(1519): threadid=10: thread exiting with uncaught exception (group=0x40014760)
06-27 17:05:15.821: E/AndroidRuntime(1519): FATAL EXCEPTION: AsyncTask #2
06-27 17:05:15.821: E/AndroidRuntime(1519): java.lang.RuntimeException: An error occured while executing doInBackground()
06-27 17:05:15.821: E/AndroidRuntime(1519): at android.os.AsyncTask$3.done(AsyncTask.java:266)
06-27 17:05:15.821: E/AndroidRuntime(1519): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
06-27 17:05:15.821: E/AndroidRuntime(1519): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
06-27 17:05:15.821: E/AndroidRuntime(1519): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
06-27 17:05:15.821: E/AndroidRuntime(1519): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
06-27 17:05:15.821: E/AndroidRuntime(1519): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1081)
06-27 17:05:15.821: E/AndroidRuntime(1519): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:574)
06-27 17:05:15.821: E/AndroidRuntime(1519): at java.lang.Thread.run(Thread.java:1020)
06-27 17:05:15.821: E/AndroidRuntime(1519): Caused by: java.lang.NullPointerException
06-27 17:05:15.821: E/AndroidRuntime(1519): at com.si.gtc.Feeds$DownloadJSON.doInBackground(Feeds.java:87)
06-27 17:05:15.821: E/AndroidRuntime(1519): at com.si.gtc.Feeds$DownloadJSON.doInBackground(Feeds.java:1)
06-27 17:05:15.821: E/AndroidRuntime(1519): at android.os.AsyncTask$2.call(AsyncTask.java:252)
06-27 17:05:15.821: E/AndroidRuntime(1519): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
06-27 17:05:15.821: E/AndroidRuntime(1519): ... 4 more
在不同的活动中，有两个json响应同时起作用。如果我运行单个响应，则Null指针错误不会影响我的输出。
第一个活动包含tabhost（Tab）。第一个选项卡（默认选项卡）具有另一个异步任务。
这是我的第一个包含Json调用和Tab主机的活动。
public class Login_Header extends TabActivity
{
Button Find;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
//To show Custom Title as image
requestWindowFeature(Window.FEATURE_CUSTOM_TITLE);
//getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
setContentView(R.layout.login_header_bar);
super.onCreate(savedInstanceState);
getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.custom_title_about_tab);
// Font size has been changed through Styles.xml for tab
TabHost tabHost = getTabHost();
Intent feeds = new Intent(this,Feeds.class);
tabHost.addTab(tabHost.newTabSpec("Tab1")
.setIndicator("Feeds")
.setContent(feeds));
Intent challenges = new Intent(this,Challenges.class);
tabHost.addTab(tabHost.newTabSpec("Tab2")
.setIndicator("Challenges")
.setContent(challenges));
Intent friends = new Intent(this,Friends.class);
tabHost.addTab(tabHost.newTabSpec("Tab3")
.setIndicator("Friends")
.setContent(friends));
Intent group = new Intent(this,Groups.class);
tabHost.addTab(tabHost.newTabSpec("Tab4")
.setIndicator("Groups")
.setContent(group));
Intent details = new Intent(this,Details.class);
tabHost.addTab(tabHost.newTabSpec("Tab5")
.setIndicator("Details")
.setContent(details));
tabHost.setCurrentTab(0);
Find.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
// TODO Auto-generated method stub
Intent find = new Intent(Login_Header.this,Find.class);
startActivity(find);
}
});
//To call async task
callNotificationCount();
}
private void callNotificationCount()
{
new NotificationCount_Async().execute("");
}
private class NotificationCount_Async extends AsyncTask<String, Void, String>
{
@Override
protected String doInBackground(String... params)
{
try
{
URL url=new URL(getString(R.string.WebServiceURL)+"/notifications/notificationcount");
HttpPost httppost = new HttpPost(url.toString());
HttpResponse responsePOST = LoginPage.httpClient.execute(httppost);
HttpEntity resEntity = responsePOST.getEntity();
InputStream instream = resEntity.getContent();
String result = convertStreamToString(instream);
Log.i("User Feed",result);
return result;
}
catch(Exception ex)
{
Log.e("error", "error", ex);
return null;
}
}
@Override
protected void onPostExecute(String result)
{
try {
JSONObject json = new JSONObject(result);
//Below code is for user count
JSONObject userNotificationjson = json.getJSONObject("user_notification");
if(json.has("user_notification"))
{
String userCount = userNotificationjson.getString("count");
int Count = Integer.parseInt(userCount);
if(Count > 0)
{
LinearLayout llUserCount = (LinearLayout)findViewById(R.id.llUserCount);
TextView userCountTextView =(TextView)findViewById(R.id.txtUserCount);
llUserCount.setVisibility(View.VISIBLE);
userCountTextView.setText(userCount);
}
}
}
private String convertStreamToString(InputStream is)
{
//code
}
现在这是我的第二个活动，Default Tab活动，它再次有json请求。
public class Feeds extends Activity
{
SessionManager session;
String custom_phpsess_id,logged_in_id_User,returnString;
// Declare Variables
JSONObject jsonobject;
JSONArray jsonarray;
ListView listview;
ListViewAdapter adapter;
ProgressDialog mProgressDialog;
ArrayList<HashMap<String, String>> arraylist;
static String FIRST_NAME = "firstname";
static String LAST_NAME = "lastname";
static String ACTION = "action";
// static String ACTIVITY_NAME = "activity_name";
static String IMAGE_URL = "image";
static String USER_ID = "user_id";
static String ACTIVITY_NAME = "activityname";
String strUrl = =new URL(getString(R.string.WebServiceURL)+"/users/userfeeds";
ListView mListView;
String id_User;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// Get the view from feeds.xml
setContentView(R.layout.feeds);
session = new SessionManager(getApplicationContext());
//To get values from session
HashMap<String, String> User = session.getUserDetails();
logged_in_id_User = User.get(SessionManager.KEY_ID);
custom_phpsess_id = User.get(SessionManager.KEY_USE);
// Creating a new non-ui thread task to download json data
// Execute DownloadJSON AsyncTask
Log.i("On Create", "Main On Create");
new DownloadJSON().execute();
}
// DownloadJSON AsyncTask
private class DownloadJSON extends AsyncTask<Void, Void, Void>
{
@Override
protected void onPreExecute()
{
Log.i("On DownloadJSON", "onPreExecute");
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(Feeds.this);
// Set progressdialog title
mProgressDialog.setTitle("");
// Set progressdialog message
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params)
{
Log.i("On doInBackground", "doInBackground");
// Create the array
arraylist = new ArrayList<HashMap<String, String>>();
// Retrive JSON Objects from the given website URL in JSONfunctions.class
jsonobject = JSONfunctions
.getJSONfromURL(strUrl);
Log.i("On doInBackground-jsonObject", jsonobject.toString());
try
{
// Locate the array name
jsonarray = jsonobject.getJSONArray("userdata");
Log.i("On doInBackground-jsonarray", jsonarray.toString());
for (int i = 0; i < jsonarray.length(); i++)
{
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
// Retrive JSON Objects
if(jsonobject.getString("actions").equals("Completed"))
{
map.put("firstname", jsonobject.getString("first_name"));
map.put("lastname", jsonobject.getString("last_name"));
map.put("action", jsonobject.getString("actions"));
map.put("image", jsonobject.getString("file_name"));
map.put("user_id", jsonobject.getString("id_user"));
map.put("activityname", jsonobject.getString("activity_name"));
Log.i("On doInBackground-Map", map.toString());
// Set the JSON Objects into the array
arraylist.add(map);
}
}
}
catch (JSONException e)
{
Log.i("On doInBackground-JSONException", e.toString());
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void args)
{
Log.i("On onPostExecute", "ON post exe");
// Locate the listview in listview_main.xml
listview = (ListView)findViewById(R.id.listview);
Log.i("On onPostExecute-onPostExecute-arraylist", arraylist.toString());
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(Feeds.this, arraylist);
Log.i("On onPostExecute-onPostExecute-Adapter", adapter.toString());
// Binds the Adapter to the ListView
listview.setAdapter(adapter);
// Close the progressdialog
mProgressDialog.dismiss();
}
}
}
和空指针行是..
行号97是= Log.i（“on doInBackground-jsonObject”，jsonobject.toString（））;