android - setSupportActionBar() throws Nullpointer exception -

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i new android , following following tutorial material design toolbar :

http://www.android4devs.com/2014/12/how-to-make-material-design-app.html

but after implementation of code. following error shown in logcat :

04-01 19:16:10.214    2246-2253/com.example.bhaskar.ddit_results e/art﹕ failed sending reply debugger: broken pipe 04-01 19:16:11.985    2246-2246/com.example.bhaskar.ddit_results e/androidruntime﹕ fatal exception: main process: com.example.bhaskar.ddit_results, pid: 2246 java.lang.runtimeexception: unable start activity componentinfo{com.example.bhaskar.ddit_results/com.example.bhaskar.ddit_results.mainactivity}: java.lang.nullpointerexception: attempt invoke virtual method 'java.lang.charsequence android.support.v7.widget.toolbar.gettitle()' on null object reference         @ android.app.activitythread.performlaunchactivity(activitythread.java:2298)         @ android.app.activitythread.handlelaunchactivity(activitythread.java:2360)         @ android.app.activitythread.access$800(activitythread.java:144)         @ android.app.activitythread$h.handlemessage(activitythread.java:1278)         @ android.os.handler.dispatchmessage(handler.java:102)         @ android.os.looper.loop(looper.java:135)         @ android.app.activitythread.main(activitythread.java:5221)         @ java.lang.reflect.method.invoke(native method)         @ java.lang.reflect.method.invoke(method.java:372)         @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:899)         @ com.android.internal.os.zygoteinit.main(zygoteinit.java:694)  caused by: java.lang.nullpointerexception: attempt invoke virtual method 'java.lang.charsequence android.support.v7.widget.toolbar.gettitle()' on null object reference         @ android.support.v7.internal.widget.toolbarwidgetwrapper.<init>(toolbarwidgetwrapper.java:95)         @ android.support.v7.internal.widget.toolbarwidgetwrapper.<init>(toolbarwidgetwrapper.java:88)         @ android.support.v7.internal.app.toolbaractionbar.<init>(toolbaractionbar.java:84)         @ android.support.v7.app.actionbaractivitydelegatebase.setsupportactionbar(actionbaractivitydelegatebase.java:175)         @ android.support.v7.app.actionbaractivity.setsupportactionbar(actionbaractivity.java:92)         @ com.example.bhaskar.ddit_results.mainactivity.oncreate(mainactivity.java:41)         @ android.app.activity.performcreate(activity.java:5933)             @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1105)         @ android.app.activitythread.performlaunchactivity(activitythread.java:2251)            @ android.app.activitythread.handlelaunchactivity(activitythread.java:2360)             @ android.app.activitythread.access$800(activitythread.java:144)         @ android.app.activitythread$h.handlemessage(activitythread.java:1278)         @ android.os.handler.dispatchmessage(handler.java:102)         @ android.os.looper.loop(looper.java:135)         @ android.app.activitythread.main(activitythread.java:5221)         @ java.lang.reflect.method.invoke(native method)         @ java.lang.reflect.method.invoke(method.java:372)         @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:899)         @ com.android.internal.os.zygoteinit.main(zygoteinit.java:694)

which caused nullpointerexception.i using android studio 1.0.1.

styles.xml :

<resources>  <!-- base application theme. --> <style name="mytheme" parent="mytheme.base">  </style>  <style name="mytheme.base" parent="theme.appcompat.light.noactionbar">      <item name="colorprimary">#ff32cd32</item>     <item name="colorprimarydark">#ff04cd2c</item>     <item name="coloraccent">#ff4081</item> </style>

v21/styles.xml:

<resources> <style name="mytheme" parent="mytheme.base">     <item name="android:windowcontenttransitions">true</item>     <item name="android:windowallowentertransitionoverlap">true</item>     <item name="android:windowallowreturntransitionoverlap">true</item>     <item name="android:windowsharedelemententertransition">@android:transition/move</item>     <item name="android:windowsharedelementexittransition">@android:transition/move</item>

in toolbar.xml i've :

<android.support.v7.widget.toolbar xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="?attr/colorprimary" app:theme="@style/themeoverlay.appcompat.dark.actionbar" app:popuptheme="@style/themeoverlay.appcompat.light" android:elevation="4dp"/>

also i've included toolbar layout in activity_main.xml file. in mainactivity.java :

public class mainactivity extends actionbaractivity {  ....    private toolbar toolbar; public static final int record_entry_request_code=3;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     // set our view "main" layout resource       toolbar = (toolbar)findviewbyid(r.id.toolbar);      //toolbar take on default actionbar characteristics     setcontentview(r.layout.activity_main);     setsupportactionbar(toolbar);     settitle("ddit_results");     ....  }

i searched problem , didn't come solutions.hopefully, recognizes error , has quick answer - otherwise can provide more information if requested.any appriciated.

you need call setcontentview before adding views such toolbar.

protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main); // <-- call first      toolbar = (toolbar)findviewbyid(r.id.toolbar); // <-- setup views after      setsupportactionbar(toolbar);     settitle("ddit_results"); }

please see official android developers blog here: http://android-developers.blogspot.com/2014/10/appcompat-v21-material-design-for-pre.html

action bar

to use toolbar action bar, first disable decor-provided action bar. easiest way have theme extend theme.appcompat.noactionbar (or light variant).

second, create toolbar instance, via layout xml:

<android.support.v7.widget.toolbar     android:id=”@+id/my_awesome_toolbar”     android:layout_height=”wrap_content”     android:layout_width=”match_parent”     android:minheight=”?attr/actionbarsize”     android:background=”?attr/colorprimary” />

the height, width, background, , on totally you; these examples. toolbar viewgroup, can style , position want.

then in activity or fragment, set toolbar act action bar:

@override public void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.blah);      toolbar toolbar = (toolbar) findviewbyid(r.id.my_awesome_toolbar);     setsupportactionbar(toolbar); }

from point on, menu items displayed in toolbar, populated via standard options menu callbacks.


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