android - setOnCheckedListener will crash my app -

i trying set toggle-button. created button in xml-file, when activate setoncheckedchangelistener(this); app crashs.

if comment out, there no problem run app.

layout:

    <?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:id="@+id/layout">       <textview         android:id="@+id/textview2"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="crunch"         android:textappearance="?android:attr/textappearancelarge" />      <scrollview                 android:id="@+id/scrollview1"                 android:layout_width="wrap_content"                 android:layout_height="match_parent" >                  <linearlayout                     android:layout_width="match_parent"                     android:layout_height="match_parent"                     android:orientation="vertical" >        <horizontalscrollview         android:id="@+id/horizontalscrollview1"         android:layout_width="wrap_content"         android:layout_height="wrap_content" >          <linearlayout             android:layout_width="match_parent"             android:layout_height="match_parent"             android:orientation="horizontal" >                     <imageview         android:id="@+id/imageview2"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:src="@drawable/ic_launcher" />      <imageview         android:id="@+id/imageview1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:src="@drawable/ic_launcher" />          </linearlayout>     </horizontalscrollview>      <textview         android:id="@+id/textview1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="@string/crunch" />        <textview         android:id="@+id/tvtimer"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="" />      <togglebutton         android:id="@+id/togglebutton1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:textoff="pause"         android:texton="play" />   </linearlayout>             </scrollview>  </linearlayout> 

activity:

public class oberklasse extends activity implements oninitlistener, oncheckedchangelistener {  public texttospeech tts; togglebutton t; linearlayout l;   protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     tts = new texttospeech(this, this);     //start und stop button     t=(togglebutton) findviewbyid(r.id.togglebutton1);     t.setoncheckedchangelistener(this);     l=(linearlayout)findviewbyid(r.id.layout);      }         @override public void oncheckedchanged(compoundbutton buttonview, boolean ischecked) {     // todo auto-generated method stub     if (ischecked) {         l.setbackgroundcolor(color.blue);     } else {         l.setbackgroundcolor(color.black);     } } 

error-code:

    03-24 23:23:52.544: e/androidruntime(1787): fatal exception: main 03-24 23:23:52.544: e/androidruntime(1787): java.lang.runtimeexception: unable start activity componentinfo{com.example.bikinifigur2/de.basti12354.tage.uebungen.tag1}: java.lang.nullpointerexception 03-24 23:23:52.544: e/androidruntime(1787):     @ android.app.activitythread.performlaunchactivity(activitythread.java:2211) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.app.activitythread.handlelaunchactivity(activitythread.java:2261) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.app.activitythread.access$600(activitythread.java:141) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.app.activitythread$h.handlemessage(activitythread.java:1256) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.os.handler.dispatchmessage(handler.java:99) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.os.looper.loop(looper.java:137) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.app.activitythread.main(activitythread.java:5103) 03-24 23:23:52.544: e/androidruntime(1787):     @ java.lang.reflect.method.invokenative(native method) 03-24 23:23:52.544: e/androidruntime(1787):     @ java.lang.reflect.method.invoke(method.java:525) 03-24 23:23:52.544: e/androidruntime(1787):     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:737) 03-24 23:23:52.544: e/androidruntime(1787):     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:553) 03-24 23:23:52.544: e/androidruntime(1787):     @ dalvik.system.nativestart.main(native method) 03-24 23:23:52.544: e/androidruntime(1787): caused by: java.lang.nullpointerexception 03-24 23:23:52.544: e/androidruntime(1787):     @ de.basti12354.tage.uebungen.oberklasse.oncreate(oberklasse.java:36) 03-24 23:23:52.544: e/androidruntime(1787):     @ de.basti12354.tage.uebungen.tag1.oncreate(tag1.java:45) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.app.activity.performcreate(activity.java:5133) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1087) 03-24 23:23:52.544: e/androidruntime(1787):     @ android.app.activitythread.performlaunchactivity(activitythread.java:2175) 03-24 23:23:52.544: e/androidruntime(1787):     ... 11 more 

the problem haven't called setcontentview(r.layout.<layout-file-name>) before finding , storing references view.