I am trying to display a list in my main activity using a ListFragment. The list is populated by my custom ArrayAdapter that uses a custom object. I am having trouble getting this list to show in the app. When I debug, it doesn't show any errors but the app immediately crashes.
Here is my fragment
Edit: I have tried several responses and have narrowed down the issue to the momentObjectListView.setAdapter(momentObjectAdapter) in the ListViewFragment. I cannot find a reason why the momentObjectAdapter would be null so it must be momentObjectListView however I cannot find where the issue stems. Any help would be much appreciated. My activity_main.xml, fragment, main activity, and adapter code are all included.
public class ListViewFragment extends ListFragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Activity myAct = getActivity();
View view = inflater.inflate(R.layout.activity_main, container, false);
ListView momentObjectListView = (ListView)view.findViewById(R.id.list_item);
//ListView momentObjectListView = getListView();
MomentObjectAdapter momentObjectAdapter = new MomentObjectAdapter(myAct, R.layout.moment_object_list_item);
//momentObjectListView.setAdapter(momentObjectAdapter);
List<MomentObject> myMoments = getMoments();
for(final MomentObject entry : myMoments) {
momentObjectAdapter.add(entry);
}
//ListViewFragment.this.setListAdapter(momentObjectAdapter);
momentObjectListView.setAdapter(momentObjectAdapter);
return view;
}
private List<MomentObject> getMoments() {
// Let's setup some test data.
// Normally this would come from some asynchronous fetch into a data source
// such as a sqlite database, or an HTTP request
final List<MomentObject> entries = new ArrayList<MomentObject>();
for(int i = 1; i < 50; i++) {
entries.add(
new MomentObject(
"Test Entry " + i,
"Anonymous Author",
new GregorianCalendar(2011, 11, i).getTime(),
R.drawable.photoicon
)
);
}
return entries;
}
}
And here is my activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".MainActivity"
android:background="#ffffffff">
<fragment android:name="com.malatras.moment2.ListViewFragment"
android:id="#+id/list"
android:layout_weight="1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
Please let me know if there is anything I need to provide to solve this.
LogCat:
e02-24 18:54:29.119 2325-2325/com.malatras.moment2 I/art﹕ Not late-enabling -Xcheck:jni (already on)
02-24 18:54:29.191 2325-2325/com.malatras.moment2 D/AndroidRuntime﹕ Shutting down VM
02-24 18:54:29.191 2325-2325/com.malatras.moment2 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.malatras.moment2, PID: 2325
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.malatras.moment2/com.malatras.moment2.MainActivity}: android.view.InflateException: Binary XML file line #9: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: android.view.InflateException: Binary XML file line #9: Error inflating class fragment
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:377)
at android.app.Activity.setContentView(Activity.java:2144)
at com.malatras.moment2.MainActivity.onCreate(MainActivity.java:11)
at android.app.Activity.performCreate(Activity.java:5933)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at com.malatras.moment2.ListViewFragment.onCreateView(ListViewFragment.java:34)
at android.app.Fragment.performCreateView(Fragment.java:2053)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:870)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1045)
at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1147)
at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2116)
at android.app.Activity.onCreateView(Activity.java:5282)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:377)
at android.app.Activity.setContentView(Activity.java:2144)
at com.malatras.moment2.MainActivity.onCreate(MainActivity.java:11)
at android.app.Activity.performCreate(Activity.java:5933)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
MainActivity:
public class MainActivity extends ListActivity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MomentObjectAdapter:
public final class MomentObjectAdapter extends ArrayAdapter<MomentObject> {
private final int momentObjectLayoutResource;
public MomentObjectAdapter(final Context context, final int momentObjectLayoutResource) {
super(context, 0);
this.momentObjectLayoutResource = momentObjectLayoutResource;
}
#Override
public View getView(final int position, final View convertView, final ViewGroup parent) {
// We need to get the best view (re-used if possible) and then
// retrieve its corresponding ViewHolder, which optimizes lookup efficiency
final View view = getWorkingView(convertView);
final ViewHolder viewHolder = getViewHolder(view);
final MomentObject entry = getItem(position);
// Setting the title view is straightforward
viewHolder.titleView.setText(entry.getTitle());
// Setting the subTitle view requires a tiny bit of formatting
final String formattedSubTitle = String.format("By %s on %s",
entry.getAuthor(),
DateFormat.getDateInstance(DateFormat.SHORT).format(entry.getPostDate())
);
viewHolder.subTitleView.setText(formattedSubTitle);
// Setting image view is also simple
viewHolder.imageView.setImageResource(entry.getIcon());
return view;
}
private View getWorkingView(final View convertView) {
// The workingView is basically just the convertView re-used if possible
// or inflated new if not possible
View workingView = null;
if(null == convertView) {
final Context context = getContext();
final LayoutInflater inflater = (LayoutInflater)context.getSystemService
(Context.LAYOUT_INFLATER_SERVICE);
workingView = inflater.inflate(momentObjectLayoutResource, null);
} else {
workingView = convertView;
}
return workingView;
}
private ViewHolder getViewHolder(final View workingView) {
// The viewHolder allows us to avoid re-looking up view references
// Since views are recycled, these references will never change
final Object tag = workingView.getTag();
ViewHolder viewHolder = null;
if(null == tag || !(tag instanceof ViewHolder)) {
viewHolder = new ViewHolder();
viewHolder.titleView = (TextView) workingView.findViewById(R.id.moment_object_title);
viewHolder.subTitleView = (TextView) workingView.findViewById(R.id.moment_object_subtitle);
viewHolder.imageView = (ImageView) workingView.findViewById(R.id.moment_object_icon);
workingView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) tag;
}
return viewHolder;
}
/**
* ViewHolder allows us to avoid re-looking up view references
* Since views are recycled, these references will never change
*/
private static class ViewHolder {
public TextView titleView;
public TextView subTitleView;
public ImageView imageView;
}
}
moment_object_list_item:
<?xml version="1.0" encoding="utf-8"?>
<!-- Layout for individual news entries in a list -->
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<!-- Icon shown next to the title/subtitle -->
<ImageView
android:id="#+id/moment_object_icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:padding="3dp" />
<!-- Title of the news entry -->
<TextView
android:id="#+id/moment_object_title"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_toRightOf="#id/moment_object_icon"
android:layout_alignTop="#id/moment_object_icon"
android:layout_margin="5dp"
android:textSize="14sp"
android:textStyle="bold" />
<!-- Subtitle contains author and date -->
<TextView
android:id="#+id/moment_object_subtitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#id/moment_object_title"
android:layout_below="#id/moment_object_title"
android:textSize="12sp" />
</RelativeLayout>
This code I don't like and not compatible with your method getMoments is:
for(final MomentObject entry : getMoments()) {
momentObjectAdapter.add(entry);
}
For now try this for a quick sample fix:
List<MomentObject> myMoments = getMoments();
for(final MomentObject entry : myMoments) {
The reason is getMoments() in the for loop is evaluated dynamically. I think so even though you declared it with final.
In the log,
Attempt to invoke virtual method 'void
android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a
null object reference
I believe object momentObjectListView is null. I could not find the UI in fragment_list_view.xml. It is however in activity_main.xml. Sample code :
View view = inflater.inflate(R.layout.activity_main, container, false);
ListView momentObjectListView = (ListView)view.findViewById(R.id.list);
Sample layout element for a ListFragment in activity_main:
<fragment android:name="com.malatras.moment2.ListViewFragment"
android:id="#+id/list"
...>
A good webpage for explaining layouts is required for understanding the basics # Layouts .
Change in your XML file this line : android:id="#+id/list"
to:
android:id="#id/android:list
and in ListViewFragment change this : ListView momentObjectListView =(ListView)view.findViewById(R.id.list);
to this:
ListView momentObjectListView = (ListView)view.findViewById(android.R.id.list);
In your Logcat file, it says
android.view.InflateException: Binary XML file line #9: Error
inflating class fragment
This means an xml file is not proper. Also deeper in the log,
The code MainActivity.onCreate(MainActivity.java:11)
...
Caused by: java.lang.NullPointerException: Attempt to invoke virtual
method 'void
android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a
null object reference at
com.malatras.moment2.ListViewFragment.onCreateView(ListViewFragment.java:34)
...
ListViewFragment.onCreateView(ListViewFragment.java:34)
Need to load file ListViewFragment.java too. In order to save time, perhaps post more files.
Another possible good code change is to modify ListViewFragment definition from:
public class ListViewFragment extends ListFragment {
to:
public class ListViewFragment extends Fragment implements AbsListView.OnItemClickListener {
The OnItemClickListener is optional.
The reason I say this is that MainActivity already hosts ListView object through ListActivity. Another reason, Android Studio wizard generates the "to" suggested code. And it sounds good to me.
Another way is to remove ListActivity from MainActivity to just Activity, with the same reason.
All these suggestions may be considered to be code style however.
Related
I am new at android and I can't seem to understand one thing.
I am trying to jump from MainActivity to MainFragment. In it there is a button. When onClickListener is triggered, it should jump to another ResultFragment. But I can't seem to understand how to do it.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.something.MainActivity">
<fragment
android:id="#+id/container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:layout="#layout/fragment_main" />
</RelativeLayout>
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Fragment fragment = new MainFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment, null).commit();
}
}
public class MainFragment extends Fragment {
public MainFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
Button button = (Button) rootView.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(getContext(), "iskviesta", Toast.LENGTH_SHORT).show();
getFragmentManager().beginTransaction().replace(R.id.container, new ResultFragment()).commit();
}
});
return rootView;
}
}
public class ResultFragment extends Fragment {
public ResultFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_result, container, false);
return rootView;
}
}
What am I doing wrong? The app doesn't even start.
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.something, PID: 14245
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.something/com.something.MainActivity}: android.view.InflateException: Binary XML file line #13: Binary XML file line #13: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: android.view.InflateException: Binary XML file line #13: Binary XML file line #13: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #13: Error inflating class fragment
Caused by: java.lang.NullPointerException
at java.lang.VMClassLoader.findLoadedClass(Native Method)
at java.lang.ClassLoader.findLoadedClass(ClassLoader.java:742)
at java.lang.ClassLoader.loadClass(ClassLoader.java:362)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at android.support.v4.app.Fragment.isSupportFragmentClass(Fragment.java:459)
at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:3321)
at android.support.v4.app.FragmentController.onCreateView(FragmentController.java:120)
at android.support.v4.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:378)
at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:33)
at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:79)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:777)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:858)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)
at android.view.LayoutInflater.inflate(LayoutInflater.java:518)
at android.view.LayoutInflater.inflate(LayoutInflater.java:426)
at android.view.LayoutInflater.inflate(LayoutInflater.java:377)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:288)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:143)
at com.something.MainActivity.onCreate(MainActivity.java:12)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
In your xml use a FrameLayout instead of Fragment:
<FrameLayout
android:id="#+id/container"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
Using a fragment tag will not allow you to do fragment transactions on the view.
You should use getSupportFragmentManager() instead of getFragmentManager in your listener :
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(getContext(), "iskviesta", Toast.LENGTH_SHORT).show();
getSupportFragmentManager().beginTransaction().replace(R.id.container, new ResultFragment()).commit();
}
});
And remplace your fragment layout with a FrameLayout in your xml code.
Hope this helps.
Sorry for my english.
I am trying to link a Fragment, RecycleView and CardView using a variation of the tutorial found on:
http://www.treyrobinson.net/blog/android-l-tutorials-part-3-recyclerview-and-cardview/
Unfortunately my app crashes with the following error message:
"java.lang.IllegalStateException: RecyclerView has no LayoutManager"
I am fairly new with Android development. I tried to find similar issues on Stackoverflow but am unable to find the issue. Any help would be greatly appreciated!
Layout of the main activity: "activity_library.xml":
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".LibraryActivity">
<android.support.v7.widget.RecyclerView
android:id="#+id/library_activity_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".LibraryActivity"
/>
</RelativeLayout>
The main activity class "LibraryActivity.java":
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
public class LibraryActivity extends AppCompatActivity{
private static final String TAG = LibraryActivity.class.getSimpleName();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); /**Create the activity and populate the savedInstanceState if the activity existed but has been destroyed (otherwise savedInstanceState will return 'null'*/
setContentView(R.layout.activity_library); /** Call to the XML layout library which display the activity */
if (savedInstanceState != null) {
// Restore value of members from saved state
} else {
// Probably initialize members with default values for a new instance
}
try {
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
BooksFragment bookFragment = new BooksFragment();
fragmentTransaction.add(R.id.library_activity_recycler_view,bookFragment);
/*The line below is the one generating the error - java.lang.IllegalStateException: RecyclerView has no LayoutManager*/
fragmentTransaction.commit();
}
catch(Exception e){
Log.d(TAG,"[ERROR] " + e.getMessage());
}
}
}
The layout of the fragment "fragment_books.xml":
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<android.support.v7.widget.RecyclerView
android:id="#+id/Book_Recycler_View"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
And the fragment class:
import android.app.Fragment;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class BooksFragment extends Fragment {
public BooksFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.activity_library, container, false);
LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
RecyclerView bookRecycler = (RecyclerView) v.findViewById(R.id.library_activity_recycler_view);
bookRecycler.setLayoutManager(layoutManager);
BookRecyclerViewAdapter adapter = new BookRecyclerViewAdapter();
bookRecycler.setAdapter(adapter);
/*In the line below should we return the view 'v' or the RecyclerView 'bookRecycler'??*/
return bookRecycler;
}
}
As I said I am fairly new to Android and therefore apologies if my code contains quite a few errors. Thanks for your help!
For reference the complete error log:
04-18 14:04:52.323 11225-11225/com.wldtaster.tellmeastory E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.wldtaster.tellmeastory, PID: 11225
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.wldtaster.tellmeastory/com.wldtaster.tellmeastory.LibraryActivity}: java.lang.IllegalStateException: RecyclerView has no LayoutManager
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.IllegalStateException: RecyclerView has no LayoutManager
at android.support.v7.widget.RecyclerView.generateLayoutParams(RecyclerView.java:3393)
at android.view.LayoutInflater.inflate(LayoutInflater.java:492)
at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
at com.wldtaster.tellmeastory.BooksFragment.onCreateView(BooksFragment.java:23)
at android.app.Fragment.performCreateView(Fragment.java:2053)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:894)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.app.BackStackRecord.run(BackStackRecord.java:834)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1452)
at android.app.Activity.performStart(Activity.java:6005)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2288)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
You must return the view ie. v in the onCreateView method of the Fragment inherited class.
I'm working on an application for android in Android Studio and I'm attempting to make an on-click listener like so:
Button menu_button = (Button)findViewById(R.id.menu_button);
menu_button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
}
});
However, when I start genymotion it tells me that the app has stopped working. If I remove this code:
menu_button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
}
});
The application runs fine. I'm very confused and was hoping maybe someone could point something out I'm not understanding.
Here's the full code of the main activity I'm working on, and I should note that the button is inside a ViewPager.
public class MainActivity extends FragmentActivity {
private ViewPager m_BackgroundViewPager;
private ViewPager m_PanelViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature((int) Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
m_BackgroundViewPager = (ViewPager)(findViewById(R.id.mainViewPager));
m_PanelViewPager = (ViewPager)(findViewById(R.id.bottomViewPager));
m_BackgroundViewPager.setAdapter
(new BackgroundPagerAdapter(getSupportFragmentManager(), this));
m_PanelViewPager.setAdapter
(new PanelPagerAdapter(getSupportFragmentManager(), this));
Button menu_button = (Button)findViewById(R.id.menu_button);
menu_button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
}
});
}
}
LogCat Results:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at eqlogic.annswingsandthings.MainActivity.onCreate(MainActivity.java:37)
at android.app.Activity.performCreate(Activity.java:5933)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
XML:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#998822">
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:id="#+id/menu_button"
android:text="Menu"
android:textSize="12dp" />
</FrameLayout>
Create a global variable for your Button as follows :
Button menu_button;
Then in your onCreate() you add this line :
menu_button = (Button)findViewById(R.id.menu_button);
And now whenever you want to make a setOnClickListener() you can do it like you were doing :
menu_button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Your click stuff
}
});
EDIT
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
Make sure that in your activity_main.xml your button has this :
android:id="#+id/menu_button"
Problem is that the button is inside the view pager.
So in order to display the button either remove it out of the view pager or add it to the xml of the fragment which forms part of the view pager and inflate it in that fragment.
I'm working on dynamically setting a text of TextView in a fragment called 'ChallengeFragment' by creating a method that sets the text. Then, I call the method in FragmentActivity class to update the TextView. However, I am getting error that TextView object is null when the method is called. I am not sure why TextView is null.
Here's the logcat message:
16:36:02.437 4072-4072/eie.android.crunch E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: eie.android.crunch, PID: 4072
java.lang.RuntimeException: Unable to start activity ComponentInfo{eie.android.crunch/eie.android.crunch.ChallengePage}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at eie.android.crunch.ChallengeFragment.setNameText(ChallengeFragment.java:76)
at eie.android.crunch.ChallengePage.onCreate(ChallengePage.java:50)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Here is the Fragment class (ChallengeFragment.java):
public class ChallengeFragment extends Fragment {
private Activity mActivity;
private TextView nameText;
private Handler handler =new Handler();
public ChallengeFragment() {
}
public void onAttach(Activity activity) {
super.onAttach(activity);
mActivity = activity;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
LayoutInflater lf = getActivity().getLayoutInflater();
View v = lf.inflate(R.layout.fragment_challenge, null);
nameText = (TextView) v.findViewById(R.id.user_name_text_view);
....
return v;
}
public void setNameText(String s) {
nameText.setText(s);
}
public TextView getNameText() {
return nameText;
}
}
And this is the code for FragmentActivity that updates the text of TextView (ChallengePage.java):
public class ChallengePage extends FragmentActivity {
private FriendChallengeFragment initialFriendHabit;
private ChallengeFragment friendHabit;
private ChallengeFragment myHabit;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_challenge);
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fm.beginTransaction();
myHabit = new ChallengeFragment();
initialFriendHabit = new FriendChallengeFragment();
myHabit.onAttach(ChallengePage.this);
initialFriendHabit.onAttach(ChallengePage.this);
fragmentTransaction
.replace(R.id.my_habit, myHabit ,"fragment_top")
.replace(R.id.friend_habit, initialFriendHabit, "fragment_bottom")
.commit();
Intent intent = getIntent();
String challengedUsername = intent.getStringExtra("username");
if(challengedUsername != null) {
friendHabit = new ChallengeFragment();
friendHabit.onAttach(ChallengePage.this);
fragmentTransaction.replace(R.id.friend_habit, friendHabit, "fragment_bottom");
friendHabit.setNameText(challengedUsername);
}
}
}
And this is the layout file that contains the fragment (fragment_challenge.xml):
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#color/white"
android:id="#+id/user_name_text_view"
android:layout_gravity="center_horizontal"
android:text="User Name"
android:textSize="30dp"
android:layout_marginTop="30dp"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#color/white"
android:id="#+id/habit_name_text"
android:layout_gravity="center_horizontal"
android:text="Habit Name"
android:textSize="40dp"
android:layout_marginTop="20dp"/>
<ProgressBar
android:layout_height="wrap_content"
android:layout_width="312dp"
style="#android:style/Widget.ProgressBar.Horizontal"
android:id="#+id/progressBar"
android:layout_marginTop="50dp"
android:layout_gravity="center_horizontal"/>
</LinearLayout>
I've looked at other stackoverflow questions relating to this but could not find answers.
The problem is your fragment's setNameText() method is called before onCreateView() has run, so your TextView has not been initialized yet. You have to wait until later to set the name text.
If you always have the name text when you are creating and adding the fragment, then it's better to pass that as an argument to the fragment and have it set the text of the TextView at the appropriate time. Something like this:
public class ChallengeFragment extends Fragment {
public static ChallengeFragment newInstance(String name) {
ChallengeFragment fragment = new ChallengeFragment();
Bundle args = new Bundle();
args.putString("username", name);
fragment.setArguments(args);
return fragment;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
Bundle args = getArguments();
if (args != null) {
String name = args.getString("username");
nameText.setText(name);
}
}
// everything else
}
A few things to note:
Do not create a constructor. Fragments need to have a default (no argument) constructor so that Android can instantiate them. This newInstance pattern is typically regarded as the best practice.
Use onActivityCreated because at that time you know the Activity is created and that the fragment's view hierarchy has been created.
Fragment arguments persist across configuration changes, so you shouldn't need to do anything special for that.
Also, you should not be calling onAttach() yourself, that's a lifecycle method that the OS calls on your fragment.
This question already has answers here:
Your content must have a ListView whose id attribute is 'android.R.id.list'
(7 answers)
Closed 7 years ago.
here is the EditFriends activity..........................................
package com.josephvarkey996gmail.test1;
import android.app.ListActivity;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.Window;
import android.widget.ArrayAdapter;
import com.parse.FindCallback;
import com.parse.ParseException;
import com.parse.ParseQuery;
import com.parse.ParseUser;
import java.util.List;
public class Editfriends extends ListActivity {
public static final String Tag=Editfriends.class.getSimpleName();
protected List<ParseUser> mUser;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.activity_editfriends);
}
#Override
protected void onResume() {
super.onResume();
setProgressBarIndeterminateVisibility(true);
ParseQuery<ParseUser> query= ParseUser.getQuery();
query.orderByAscending(ParseConstants.key_Username);
query.setLimit(1000);
query.findInBackground(new FindCallback<ParseUser>() {
#Override
public void done(List<ParseUser> users, ParseException e) {
setProgressBarIndeterminateVisibility(true);
if (e== null){
mUser=users;
String[] username = new String[mUser.size()];
int i=0;
for(ParseUser user:mUser){
username[i]=user.getUsername();
i++;
}
ArrayAdapter<String> adapter = new ArrayAdapter<>(Editfriends.this,android.R.layout.simple_list_item_checked,username);
setListAdapter(adapter);
}
else
{
Log.e(Tag,e.getMessage());
AlertDialog.Builder builder=new AlertDialog.Builder(Editfriends.this);
builder.setMessage(e.getMessage()).setTitle(R.string.error_title).setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_editfriends, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
here is the xml of Editfriends ............................................
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context="com.josephvarkey996gmail.test1.Editfriends">
<TextView android:text="#string/hello_world" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
im learning ,so cant understand the eror. here is the logcat..............................
07-21 19:42:05.397 9188-9188/com.josephvarkey996gmail.test1 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.josephvarkey996gmail.test1, PID: 9188
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.josephvarkey996gmail.test1/com.josephvarkey996gmail.test1.Editfriends}: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list'
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list'
at android.app.ListActivity.onContentChanged(ListActivity.java:243)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:382)
at android.app.Activity.setContentView(Activity.java:2145)
at com.josephvarkey996gmail.test1.Editfriends.onCreate(Editfriends.java:27)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Your main activity class is extending a ListActivity. This means that your xml file needs a ListView.
Try adding something like this to your XML:
<ListView android:id="#android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
More information can be found at http://developer.android.com/reference/android/app/ListActivity.html.
As the documentation states:
ListActivity has a default layout that consists of a single, full-screen list in the center of the screen. However, if you desire, you can customize the screen layout by setting your own view layout with setContentView() in onCreate(). To do this, your own view MUST contain a ListView object with the id "#android:id/list
Your activtiy extends ListActivity. So as the crash logs say :
Your content must have a ListView whose id attribute is 'android.R.id.list'
This mean that in your xml file you should have a ListView with the attribute android:id:"android.R.id.list.
This is because ListActivity expect to find a ListView in is content view.
You are using a ListActivity, which is a bit different than a normal Activity.
If you do nothing, then your ListActivity will have a single View in it, which is a ListView.
If you call setContentView() to supply your own layout (perhaps you want to display more than just a ListView), then your layout must contain a ListView and that ListView must have an id of #android:id/list.
Since you are providing a custom layout that consists of a RelativeLayout with a single TextView, your layout does not pass this requirement. Since it looks like you just have placeholder content there, I would remove the layout and remove the call to setContentView().
The exception you posted from your logcat mentions this:
Your content must have a ListView whose id attribute is 'android.R.id.list'