问题
I have converted Many Activities to Fragment, all are working fine except one. It gives Null Pointer Exception on setOnItemClickListener. I have checked many similar questions, but unable to figure out the problem. If anyone can provide correct code with explanation for problem.
Problem is at this line as given by debugger:
lv.setOnItemClickListener(new OnItemClickListener() {
Following is Code:
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.GradientDrawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import java.io.InputStreamReader;
import java.net.URL;
import java.io.BufferedReader;
import java.net.URLConnection;
import android.support.v4.app.Fragment;
public class listtojson extends Fragment {
private ProgressDialog pDialog;
public static String url = "http://www.newsvoice.in/upload_audio_sawdhan/listnews.php";
// JSON Node names
private static final String TAG_CONTACTS = "contacts";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_SIZE = "size";
private static final String TAG_PHONE_URL = "url";
private static final String TAG_FILETYPE = "filetype";
private static final String TAG_FILETYPETXT = "filetypetxt";
private static final String TAG_DETAILS = "details";
private static final String TAG_FILEPATH = "filepath";
private static final String TAG_LOCATION = "location";
private static final String TAG_DATETIME = "datetime";
private static final String TAG_USERNAME = "username";
private static final String TAG_HIGHALERT= "highalert";
public int ssid ;
// contacts JSONArray
JSONArray contacts = null;
public TextView view1;
ListView lv;
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList;
RelativeLayout llLayout;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
FragmentActivity faActivity = (FragmentActivity) super.getActivity();
llLayout = (RelativeLayout) inflater.inflate(R.layout.listnewsjson, container, false);
contactList = new ArrayList<HashMap<String, String>>();
lv = (ListView) llLayout.findViewById(R.id.list); //getListView();
// ListView lv = getActivity().getListView();
// Listview on item click listener
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
String name = ((TextView) view.findViewById(R.id.name))
.getText().toString();
String size = ((TextView) view.findViewById(R.id.size))
.getText().toString();
String description = ((TextView) view.findViewById(R.id.url))
.getText().toString();
String details = ((TextView) view.findViewById(R.id.details))
.getText().toString();
String location = ((TextView) view.findViewById(R.id.location))
.getText().toString();
String datetime = ((TextView) view.findViewById(R.id.datetime))
.getText().toString();
String filetype = ((TextView) view.findViewById(R.id.filetypetxt))
.getText().toString();
String username = ((TextView) view.findViewById(R.id.username))
.getText().toString();
Intent in = new Intent(getActivity().getApplicationContext(), jsondetailActivity.class);
// passing sqlite row id
//= in.putExtra(TAG_ID, sqlite_id);
in.putExtra(TAG_ID, String.valueOf(id));
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_DETAILS, details);
in.putExtra(TAG_LOCATION, location);
in.putExtra(TAG_DATETIME, datetime);
in.putExtra(TAG_FILETYPE, filetype);
in.putExtra(TAG_PHONE_URL, description);
in.putExtra(TAG_SIZE, size);
in.putExtra(TAG_USERNAME, username);
startActivity(in);
}
});
// Calling async task to get json
new GetContacts().execute();
return llLayout;
}
/**
* Async task class to get json by making HTTP call
* */
private class GetContacts extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Loading People News");
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
try {
// Making a request to url and getting response
// String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
URL requestUrl = new URL(url);
Log.e("Debug", " Sapp 1 : " + requestUrl.toString());
URLConnection con = requestUrl.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
StringBuilder sb=new StringBuilder();
//Reader rd=new Readable(in);
int cp;
try {
while((cp=in.read())!=-1){
sb.append((char)cp);
}}
catch(Exception e){
}
String jsonStr=sb.toString();
Log.e("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
contacts = jsonObj.getJSONArray(TAG_CONTACTS);
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String size = c.getString(TAG_SIZE);
String url = c.getString(TAG_PHONE_URL);
String details = c.getString(TAG_DETAILS);
String location = c.getString(TAG_LOCATION);
String datetime = c.getString(TAG_DATETIME);
String filetype = c.getString(TAG_FILETYPE);
String username = c.getString(TAG_USERNAME);
String highalert = c.getString(TAG_HIGHALERT);
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_ID, id);
contact.put(TAG_NAME, name);
contact.put(TAG_SIZE, size);
contact.put(TAG_PHONE_URL, url);
contact.put(TAG_DETAILS, details);
contact.put(TAG_LOCATION, location);
contact.put(TAG_DATETIME, datetime);
contact.put(TAG_FILETYPE, filetype);
contact.put(TAG_FILETYPETXT, filetype);
contact.put(TAG_USERNAME, username);
contact.put(TAG_HIGHALERT, highalert);
// adding contact to contact list
contactList.add(contact);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
}catch(Exception ec){
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
getActivity(), contactList,
R.layout.list_selector, new String[] { TAG_NAME, TAG_SIZE,
TAG_PHONE_URL,TAG_FILETYPE, TAG_FILETYPETXT,TAG_DETAILS,TAG_LOCATION,TAG_DATETIME, TAG_USERNAME, TAG_HIGHALERT}, new int[] { R.id.name,
R.id.size, R.id.url, R.id.filetype,R.id.filetypetxt, R.id.details, R.id.location, R.id.datetime, R.id.username, R.id.highalert });
Log.e("Debug", " Sapp 10"+TAG_NAME);
SimpleAdapter.ViewBinder viewBinder = new SimpleAdapter.ViewBinder() {
@Override
public boolean setViewValue(View view, Object data,
String textRepresentation) {
if (view.getId() == R.id.name) {
((TextView) view).setText((String) data);
return true;
} else if (view.getId() == R.id.size) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.url) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.details) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.location) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.datetime) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.filetypetxt) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.username) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.highalert) {
GradientDrawable gd = new GradientDrawable();
gd.setColor(0xffff0000); // Changes this drawbale to use a single color instead of a gradient
gd.setCornerRadius(0);
gd.setSize(10,20);
// view.findViewById(R.id.name).setBackgroundDrawable(gd);
String halert=(String.valueOf((String) data));
if(halert.equals("1")) {
((TextView) view).setText(" ");
((TextView) view).setBackgroundDrawable(gd);
return true;
}
else { return true; }
} else if (view.getId() == R.id.filetype) {
// (view1 = (TextView) findViewById(R.id.filetypetxt)).setText((String) data);
Resources res =getResources();
String tnew=(String.valueOf((String) data));
String tst=tnew;
int sidd=0;
// Log.e("Debug", " Sapp 7:"+(String)data+":");
if(tst.equals("c")) { ssid = R.drawable.ca; }
else if(tst.equals("d")) { ssid = R.drawable.da; }
else if(tst.equals("e")) { ssid = R.drawable.ea; }
// Log.e("Debug", " Sapp 8 :"+ssid+":");
Bitmap bmp = BitmapFactory.decodeResource(res, ssid);
BitmapDrawable ob = new BitmapDrawable(getResources(), bmp);
((ImageView) view).setImageDrawable(ob);
((ImageView) view).setImageBitmap(bmp);
return true;
}
return false;
}
};
((SimpleAdapter) adapter).setViewBinder(viewBinder);
lv.setAdapter(adapter);
registerForContextMenu(lv);
}
}
public static String getFileSize(long size) {
if (size <= 0)
return "0";
final String[] units = new String[] { "B", "KB", "MB", "GB", "TB" };
int digitGroups = (int) (Math.log10(size) / Math.log10(1024));
return new DecimalFormat("#,##0.#").format(size / Math.pow(1024, digitGroups)) + " " + units[digitGroups];
}
}
And here is the Logcat:
10-14 00:46:53.900 18286-18286/com.sjssoft.sawdhan E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.sjssoft.sawdhan, PID: 18286
java.lang.NullPointerException
at com.sjssoft.sawdhan.listtojson.onCreateView(listtojson.java:87)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:955)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:740)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:490)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1072)
at android.support.v4.view.ViewPager.populate(ViewPager.java:918)
at android.support.v4.view.ViewPager$3.run(ViewPager.java:248)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
at android.view.Choreographer.doCallbacks(Choreographer.java:574)
at android.view.Choreographer.doFrame(Choreographer.java:543)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5052)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
at dalvik.system.NativeStart.main(Native Method)
And here is XML
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:divider="#b5b5b5"
android:dividerHeight="1dp"
android:listSelector="@drawable/list_selector"
/>
</RelativeLayout>
回答1:
@android:id/list uses the ID "list" from the Android package, so you need to reference it as findViewById(android.R.id.list) in your Java code.
回答2:
Try this:
View fragment = inflater.inflate(R.layout.your_fragment_layout, container, false);
lv = (ListView) fragment.findViewById(android.R.id.list);
回答3:
Your ArrayList needs to be like this:
ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>
Instead of :
llLayout = (RelativeLayout) inflater.inflate(R.layout.listnewsjson, container, false);
insert this:
View v = inflater.inflate(R.layout.listnewsjson, container, false);
lv = (ListView) v.findViewById(android.R.id.list);
...
new GetContacts().execute();
return v;
Your AsyncTask needs to be like this:
AsyncTask<Void, Void, ArrayList<HashMap<String, String>>
Your doInBackground needs to be like this:
ArrayList<HashMap<String, String>> doInBackground(Void... params)
Your onPostExecute needs to be like this:
onPostExecute(ArrayList<HashMap<String, String>> result)
set adapter:
lv.setAdapter(new SomeAdapter(getActivity().getApplicationContext(), result));
...
来源：https://stackoverflow.com/questions/33111034/nullpointerexception-on-oncreateview-when-using-fragment-and-listview