android - Why is it showing that TextView object is null? -
i making app in in using fragments. have made in portrait in landscape mode.
in portrait mode have done listview shown , on selecting item on next activity description shown
in landscape mode have used 2 fragments in same activity in 1 fragment has listview , second fragment has description
but when clicking item in list view showing me error
cannot invoke method on null textview object but have initialised n onactivitycreated() method in fragment2.java why giving error?
main.xml (portrait)
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.grepthor.fragment4.mainactivity"> <fragment android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/fragment1" android:name="com.grepthor.fragment4.fragment1" /> </linearlayout> main.xml (landscape)
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="match_parent"> <fragment android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="1" android:id="@+id/fragment1" android:name="com.grepthor.fragment4.fragment1"/> <fragment android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="1" android:id="@+id/fragment2" android:name="com.grepthor.fragment4.fragment2"/> </linearlayout> main.java
import android.app.fragmentmanager; import android.content.intent; import android.support.v7.app.appcompatactivity; import android.os.bundle; public class mainactivity extends appcompatactivity implements fragment1.communicator { fragment1 f1; fragment2 f2; fragmentmanager fm; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); fm=getfragmentmanager(); f1= (fragment1) fm.findfragmentbyid(r.id.fragment1); f1.setcommunicator(this); } @override public void respond(int position) { f2= (fragment2) fm.findfragmentbyid(r.id.fragment2); if(f2!=null && f2.isvisible()) { f2.changedata(position); } else { intent i=new intent(this,secondactivity.class); i.putextra("index",position); startactivity(i); } } } fragment1.xml
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.grepthor.fragment4.fragment1"> <listview android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/list"/> </relativelayout> fragment1.java
import android.app.fragment; import android.support.annotation.nullable; import android.support.v7.app.appcompatactivity; import android.os.bundle; import android.view.layoutinflater; import android.view.view; import android.view.viewgroup; import android.widget.adapterview; import android.widget.arrayadapter; import android.widget.listview; import android.widget.toast; public class fragment1 extends fragment implements adapterview.onitemclicklistener { listview l; communicator comm; @nullable @override public view oncreateview(layoutinflater inflater, @nullable viewgroup container, bundle savedinstancestate) { return inflater.inflate(r.layout.activity_fragment1,container,false); } @override public void onactivitycreated(@nullable bundle savedinstancestate) { super.onactivitycreated(savedinstancestate); l= (listview) getactivity().findviewbyid(r.id.list); arrayadapter ad=arrayadapter.createfromresource(getactivity(),r.array.topic,android.r.layout.simple_list_item_1); l.setadapter(ad); // toast.maketext(getactivity(),"helo",toast.length_long).show(); l.setonitemclicklistener(this); } @override public void onitemclick(adapterview<?> parent, view view, int position, long id) { comm.respond(position); } public void setcommunicator(communicator c) { comm=c; } interface communicator { void respond(int data); } } fragment2.xml
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.grepthor.fragment4.fragment2"> <textview android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/text"/> </relativelayout> fragment2.java
public class fragment2 extends fragment { textview t; @nullable @override public view oncreateview(layoutinflater inflater, @nullable viewgroup container, bundle savedinstancestate) { return inflater.inflate(r.layout.activity_fragment2,container,false); } @override public void onactivitycreated(@nullable bundle savedinstancestate) { super.onactivitycreated(savedinstancestate); // toast.maketext(getactivity(),"helo",toast.length_long).show(); t=(textview)getactivity().findviewbyid(r.id.text); } public void changedata(int position) { string des[]= getresources().getstringarray(r.array.des); t.settext(des[position]); } } secondactivity.xml
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.grepthor.fragment4.secondactivity"> <fragment android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/fragment2" android:name="com.grepthor.fragment4.fragment2"/> </linearlayout> secondactivity.java
import android.content.intent; import android.app.fragmentmanager; import android.support.v7.app.appcompatactivity; import android.os.bundle; public class secondactivity extends appcompatactivity { @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_second); intent i=getintent(); int position=i.getextras().getint("index",0); fragmentmanager fm=getfragmentmanager(); fragment2 f2= (fragment2) fm.findfragmentbyid(r.id.fragment2); f2.changedata(position); } } strings.xml
<resources> <string name="app_name">fragment4</string> <string-array name="topic"> <item>heading</item> <item>stories</item> <item>settings</item> <item>music</item> </string-array> <string-array name="des"> <item>ldwkflkwdflkdqdvmqmdvmqdvmqlkrvqkneroqknre;qoiengqrknqrqvqfvaa</item> <item>vqdlkvnqldvnqdnvqdnvqepojpqojjoergjelgefbfmsmfv</item> <item>dwkfmnqdkwnfqkjwdnflwndfqkwheflqierqieurpqeirqrkmqwrgfqnqnmdqd</item> <item>skjsbdkafsknaslnaslfnaljfhadfkjgjhgasjdvsadablvasfgasfkgnjlkrglrgqmqbvmadbsv</item> </string-array> </resources> logcat
fatal exception: main process: com.grepthor.fragment4, pid: 31014 java.lang.runtimeexception: unable start activity componentinfo{com.grepthor.fragment4/com.grepthor.fragment4.secondactivity}: java.lang.nullpointerexception: attempt invoke virtual method 'void android.widget.textview.settext(java.lang.charsequence)' on null object reference @ android.app.activitythread.performlaunchactivity(activitythread.java:2430) @ android.app.activitythread.handlelaunchactivity(activitythread.java:2490) @ android.app.activitythread.access$900(activitythread.java:157) @ android.app.activitythread$h.handlemessage(activitythread.java:1351) @ android.os.handler.dispatchmessage(handler.java:102) @ android.os.looper.loop(looper.java:148) @ android.app.activitythread.main(activitythread.java:5437) @ java.lang.reflect.method.invoke(native method) @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:726) @ com.android.internal.os.zygoteinit.main(zygoteinit.java:616) caused by: java.lang.nullpointerexception: attempt invoke virtual method 'void android.widget.textview.settext(java.lang.charsequence)' on null object reference @ com.grepthor.fragment4.fragment2.changedata(fragment2.java:35) @ com.grepthor.fragment4.secondactivity.oncreate(secondactivity.java:21) @ android.app.activity.performcreate(activity.java:6532) @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1108) @ android.app.activitythread.performlaunchactivity(activitythread.java:2383) @ android.app.activitythread.handlelaunchactivity(activitythread.java:2490) @ android.app.activitythread.access$900(activitythread.java:157) @ android.app.activitythread$h.handlemessage(activitythread.java:1351) @ android.os.handler.dispatchmessage(handler.java:102) @ android.os.looper.loop(looper.java:148) @ android.app.activitythread.main(activitythread.java:5437) @ java.lang.reflect.method.invoke(native method) @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:726) @ com.android.internal.os.zygoteinit.main(zygoteinit.java:616)
your fragment2 has textview , you're trying find in activity. need instead in fragment2 , remove onactivitycreated() :
@override public view oncreateview(layoutinflater inflater, @nullable viewgroup container, bundle savedinstancestate) { view rootview = inflater.inflate(r.layout.activity_fragment2,container,false); textview textview = (textview) rootview.findviewbyid(r.id.text); } also in future, post relevant parts of code vs posting of it.
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