android - Trouble implementing Material Theme -

i using this tutorial implement material theme existing app on pre android 5.0 devices. problem getting null pointer exception every-time call getactionbar().something or getsupportactionbar().something.

here have done implement material theme.

in values/styles.xml

<resources xmlns:android="http://schemas.android.com/apk/res/android">  <!--     base application theme, dependent on api level. theme replaced     appbasetheme res/values-vxx/styles.xml on newer devices. --> <style name="apptheme" parent="apptheme.base"/>  <style name="apptheme.base" parent="theme.appcompat.light">     <item name="colorprimary">#1a7e99</item>     <item name="colorprimarydark">#16657a</item>        <item name="android:windownotitle">true</item>     <item name="windowactionbar">false</item>    </style>  <style name="drawerarrowstyle" parent="widget.appcompat.drawerarrowtoggle">     <item name="spinbars">true</item>     <item name="color">@android:color/white</item> </style>  <!-- view pager progress indecator theme -->  <style name="styledindicators" parent="appbasetheme">     <item name="vpicirclepageindicatorstyle">@style/customcirclepageindicator</item>  </style>   <style name="customcirclepageindicator">     <item name="fillcolor">#ffffff</item>     <item name ="strokewidth">2dp</item>      <item name ="strokecolor">#cfd3d4</item>                   <item name="radius">8dp</item>     <item name="centered">true</item> </style>  <style name="widget"></style>  <style name="widget.floatinghintedittext" parent="@android:style/widget.edittext">     <item name="android:paddingtop">0dp</item> </style> 

in values-v21/styles.xml

<?xml version="1.0" encoding="utf-8"?> <resources> <style name="apptheme" parent="apptheme.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> </style> </resources> 

as have set windowactionbar false, have toolbar layout.

toolbar.xml

<?xml version="1.0" encoding="utf-8"?> <android.support.v7.widget.toolbar xmlns:android="http://schemas.android.com/apk/res/android"   android:id="@+id/toolbar"   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:background="?attr/colorprimary"/> 

and on mainactivity.java

public class mainactivity extends actionbaractivity  {     @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);          toolbar toolbar = (toolbar) findviewbyid(r.id.toolbar);         if (toolbar != null) {             setsupportactionbar(toolbar);         }         getsupportactionbar().setdisplayhomeasupenabled(true); // null pointer exception here         getsupportactionbar().sethomebuttonenabled(true);         // rest of code     } } 

i adding theme in manifest:

android:theme="@style/apptheme" 

my logcat:

11-11 12:40:54.798: e/resourcetype(32738): style contains key bad entry: 0x01010479 11-11 12:40:55.349: e/androidruntime(32738): fatal exception: main 11-11 12:40:55.349: e/androidruntime(32738): java.lang.runtimeexception: unable start activity componentinfo{com.driverdesignstudio.drvr/com.driverdesignstudio.drvr.mainactivity}: java.lang.nullpointerexception 11-11 12:40:55.349: e/androidruntime(32738):    @ android.app.activitythread.performlaunchactivity(activitythread.java:2343) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.app.activitythread.handlelaunchactivity(activitythread.java:2395) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.app.activitythread.access$600(activitythread.java:162) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.app.activitythread$h.handlemessage(activitythread.java:1364) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.os.handler.dispatchmessage(handler.java:107) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.os.looper.loop(looper.java:194) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.app.activitythread.main(activitythread.java:5371) 11-11 12:40:55.349: e/androidruntime(32738):    @ java.lang.reflect.method.invokenative(native method) 11-11 12:40:55.349: e/androidruntime(32738):    @ java.lang.reflect.method.invoke(method.java:525) 11-11 12:40:55.349: e/androidruntime(32738):    @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:833) 11-11 12:40:55.349: e/androidruntime(32738):    @ com.android.internal.os.zygoteinit.main(zygoteinit.java:600) 11-11 12:40:55.349: e/androidruntime(32738):    @ dalvik.system.nativestart.main(native method) 11-11 12:40:55.349: e/androidruntime(32738): caused by: java.lang.nullpointerexception 11-11 12:40:55.349: e/androidruntime(32738):    @ com.driverdesignstudio.drvr.mainactivity.oncreate(mainactivity.java:123) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.app.activity.performcreate(activity.java:5122) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1081) 11-11 12:40:55.349: e/androidruntime(32738):    @ android.app.activitythread.performlaunchactivity(activitythread.java:2307) 11-11 12:40:55.349: e/androidruntime(32738):    ... 11 more 

my questions:

• why getting null pointer exception getactionbar() when adding toolbar layout mainactivity?
• how add material design theme app.

cheers, rakshak

update: actual problem have <android.support.v7.widget.toolbar code in own toolbar.xml file. has in activity_main.xml , other layouts want use actionbar.

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the toolbar allows more customization default actionbar (mostly appearance related). if want or need customize actionbar, need set toolbar actionbar. if not. dont need , can use default actionbar provided theme (you have remove windowactionbar false part theme).

if want use toolbar, have ensure there toolbar view in layouts.

<android.support.v7.widget.toolbar     xmlns:android="http://schemas.android.com/apk/res/android"     android:id="@+id/toolbar"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:background="?attr/colorprimarydark"/> 

then can use code.

but should ensure getsupportactionbar() not return null before use it. in case layout missing toolbar.

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old answer below

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toolbar toolbar = (toolbar) findviewbyid(r.id.toolbar); if (toolbar != null) {     setsupportactionbar(toolbar); } getsupportactionbar().setdisplayhomeasupenabled(true); // null pointer exception here getsupportactionbar().sethomebuttonenabled(true); 

you set toolbar if view has been found. seems view has not been found.

after if access actionbar has not been set , therefore null.

also in them have <item name="windowactionbar">false</item> disables default actionbar.

you can following:

• set windowactionbar true in theme have default actionbar , wont need toolbar.
• if want use toolbar on non default location have ensure findviewbyid(r.id.toolbar) returns toolbar (check layouts there toolbar id)
• or not use getsupportactionbar without testing null.