nullpointerexception using lv.setadapter() method
https://stackoverflow.com//questions/23051046
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21-12-2019 - |
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so I have read a lot of post here that involve this, but none of them have helped me , since usually what happends is that the listview is not created when the set adapter methos is called, but in my case I have both of them created on the same OnCreateView() which is why i do not know why i keep getting this
Here is my main activity:
package com.example.student_lists;
import java.util.ArrayList;
import java.util.Locale;
import com.resources.student_list.Student;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.NavUtils;
import android.support.v4.view.ViewPager;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.ListView;
import android.widget.TextView;
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
* will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
EditText inputSearch;
// static ListView lv;
// static EditText inputSearch;
//static MyListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(
actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
private class MyListAdapter extends ArrayAdapter<Student> implements Filterable{
private final Context context;
public ArrayList<Student> displayValues;
public ArrayList<Student> originalValues;
public MyListAdapter(Context context, int textViewResourceId, ArrayList<Student> values) {
super(context, textViewResourceId, values);
this.context = context;
this.displayValues = values;
this.originalValues = (ArrayList<Student>) values.clone();
}
public int getCount(){
return this.displayValues.size();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
//----This method sets each row of the list individually----
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View itemView = inflater.inflate(R.layout.list_view, parent, false);
if(displayValues.size() > 0)
{
Student student = displayValues.get(position);
// //Fill Name
TextView name = (TextView) itemView.findViewById(R.id.contactName);
name.setText(student.getFirstName() + student.getLastName());
}
return itemView;
}
public Filter getFilter() {
Filter contactFilter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence constraint) {
FilterResults filterResults = new FilterResults();
ArrayList<Student> filteredList = new ArrayList<Student>();
//Filter the list
if(constraint != null && originalValues !=null) {
if(!constraint.toString().isEmpty())
{
String constraintLowerCase = constraint.toString().toLowerCase();
for(Student c: originalValues)
{
String cName = c.getFirstName().toLowerCase() ;
String cLName = c.getLastName().toLowerCase();
if(cName.startsWith(constraintLowerCase) || cLName.startsWith(constraintLowerCase))
{
//Add the row to the list if filtered items
filteredList.add(c);
}
}
}
//Important steps to store the filtered list
filterResults.values = filteredList;
filterResults.count = filteredList.size();
}
return filterResults;
}
@SuppressWarnings("unchecked")
@Override
protected void publishResults(CharSequence contraint, FilterResults results) {
if (results.count > 0)
{
//Display the filtered list
MyListAdapter.this.displayValues = (ArrayList<Student>) results.values;
notifyDataSetChanged();
}
else
{
if(inputSearch.getText().toString().isEmpty())
{
//Display the original list
MyListAdapter.this.displayValues = (ArrayList<Student>) MyListAdapter.this.originalValues.clone();
}
else
{
//Display an empty list
MyListAdapter.this.displayValues.clear();
}
notifyDataSetInvalidated();
}
}
};
return contactFilter;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1);
fragment.setArguments(args);
return fragment;
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
}
return null;
}
}
/**
* A dummy fragment representing a section of the app, but that simply
* displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
public static final String ARG_SECTION_NUMBER = "section_number";
public DummySectionFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main_dummy, container, false);
switch(getArguments().getInt(ARG_SECTION_NUMBER)){
case 0:
case 1:
Student andres = new Student();
andres.setFirstName("Andres");
andres.setLastName("Blanco");
Student ondria = new Student();
ondria.setFirstName("Ondria");
ondria.setLastName("Arias");
ArrayList<Student> studentList = new ArrayList<Student>();
studentList.add(andres);
studentList.add(ondria);
MainActivity mainactivity = new MainActivity();
ListView lv = (ListView) rootView.findViewById(android.R.id.list);
//inputSearch = (EditText) rootView.findViewById(R.id.inputSearch);
MyListAdapter adapter = mainactivity.new MyListAdapter(getActivity().getBaseContext(), R.layout.list_view, studentList);
lv.setAdapter(adapter);
return rootView;
case 2:
}
return rootView;
}
}
}
and here is my LogCat report:
04-14 02:09:53.667: D/dalvikvm(1348): Late-enabling CheckJNI
04-14 02:09:53.751: D/dalvikvm(1348): GC_FOR_ALLOC freed 103K, 5% free 3073K/3232K, paused 8ms, total 9ms
04-14 02:09:53.795: D/AndroidRuntime(1348): Shutting down VM
04-14 02:09:53.795: W/dalvikvm(1348): threadid=1: thread exiting with uncaught exception (group=0xa4d01b20)
04-14 02:09:53.807: E/AndroidRuntime(1348): FATAL EXCEPTION: main
04-14 02:09:53.807: E/AndroidRuntime(1348): Process: com.example.student_lists, PID: 1348
04-14 02:09:53.807: E/AndroidRuntime(1348): java.lang.NullPointerException
04-14 02:09:53.807: E/AndroidRuntime(1348): at com.example.student_lists.MainActivity$DummySectionFragment.onCreateView(MainActivity.java:304)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.View.measure(View.java:16497)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.View.measure(View.java:16497)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-14 02:09:53.807: E/AndroidRuntime(1348): at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.View.measure(View.java:16497)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
04-14 02:09:53.807: E/AndroidRuntime(1348): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.View.measure(View.java:16497)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.Choreographer.doCallbacks(Choreographer.java:574)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.Choreographer.doFrame(Choreographer.java:544)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.os.Handler.handleCallback(Handler.java:733)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.os.Handler.dispatchMessage(Handler.java:95)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.os.Looper.loop(Looper.java:136)
04-14 02:09:53.807: E/AndroidRuntime(1348): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-14 02:09:53.807: E/AndroidRuntime(1348): at java.lang.reflect.Method.invokeNative(Native Method)
04-14 02:09:53.807: E/AndroidRuntime(1348): at java.lang.reflect.Method.invoke(Method.java:515)
04-14 02:09:53.807: E/AndroidRuntime(1348): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-14 02:09:53.807: E/AndroidRuntime(1348): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-14 02:09:53.807: E/AndroidRuntime(1348): at dalvik.system.NativeStart.main(Native Method)
04-14 02:28:04.931: D/dalvikvm(1442): GC_FOR_ALLOC freed 109K, 6% free 3067K/3232K, paused 35ms, total 35ms
04-14 02:28:05.019: D/AndroidRuntime(1442): Shutting down VM
04-14 02:28:05.019: W/dalvikvm(1442): threadid=1: thread exiting with uncaught exception (group=0xa4d01b20)
04-14 02:28:05.019: E/AndroidRuntime(1442): FATAL EXCEPTION: main
04-14 02:28:05.019: E/AndroidRuntime(1442): Process: com.example.student_lists, PID: 1442
04-14 02:28:05.019: E/AndroidRuntime(1442): java.lang.NullPointerException
04-14 02:28:05.019: E/AndroidRuntime(1442): at com.example.student_lists.MainActivity$DummySectionFragment.onCreateView(MainActivity.java:304)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.View.measure(View.java:16497)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.View.measure(View.java:16497)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-14 02:28:05.019: E/AndroidRuntime(1442): at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.View.measure(View.java:16497)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
04-14 02:28:05.019: E/AndroidRuntime(1442): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.View.measure(View.java:16497)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.Choreographer.doCallbacks(Choreographer.java:574)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.Choreographer.doFrame(Choreographer.java:544)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.os.Handler.handleCallback(Handler.java:733)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.os.Handler.dispatchMessage(Handler.java:95)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.os.Looper.loop(Looper.java:136)
04-14 02:28:05.019: E/AndroidRuntime(1442): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-14 02:28:05.019: E/AndroidRuntime(1442): at java.lang.reflect.Method.invokeNative(Native Method)
04-14 02:28:05.019: E/AndroidRuntime(1442): at java.lang.reflect.Method.invoke(Method.java:515)
04-14 02:28:05.019: E/AndroidRuntime(1442): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-14 02:28:05.019: E/AndroidRuntime(1442): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-14 02:28:05.019: E/AndroidRuntime(1442): at dalvik.system.NativeStart.main(Native Method)
Please help me find whats causing my nullpointer.
المحلول
You are defining the adapter of the listview incorrectly. It should declare a new MyListAdapter as the following:
// Declare a new adapter and define its parameters:
MyListAdapter adapter = new MyListAdapter()
Your adapter class passes the parameters context, resourceId and arraylist. The resourceId is the textview you wish to populate with the arraylist.
You should be defining an itemId, not a layout. Between the context and the ArrayList place the textview resourceId you wish to populate with the ArrayList data.
// Declare a new adapter and define its parameters:
MyListAdapter adapter = new MyListAdapter(getActivity(), R.id.YOURTVID, studentList);
// Then set the list adapter:
lv.setAdapter(adapter);
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