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My application was running perfect then suddenly error appear and i dont know what to do.. i apply different solution but nothing help.. i am making view pager with fragment and when i add button in my fragment then this error come after this i remove the button but error is not going..

slider_activity class

public class Slider_activity extends FragmentActivity {

    ViewPager viewPager = null;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.slider_activity);
         setPager(); /// line 26
    }

    private void setPager(){
        viewPager = (ViewPager) findViewById(R.id.pager);
        FragmentManager fragmentManager = getSupportFragmentManager();
        viewPager.setAdapter(new MyAdapter(fragmentManager));

    }
}

slider_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</android.support.v4.view.ViewPager>

error

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.amir.namaztimer/com.example.amir.namaztimer.Slider_activity}: java.lang.NullPointerException
                                                                               at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
                                                                               at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
                                                                               at android.app.ActivityThread.access$600(ActivityThread.java:141)
                                                                               at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                               at android.os.Looper.loop(Looper.java:137)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:5041)
                                                                               at java.lang.reflect.Method.invokeNative(Native Method)
                                                                               at java.lang.reflect.Method.invoke(Method.java:511)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
                                                                               at dalvik.system.NativeStart.main(Native Method)
                                                                            Caused by: java.lang.NullPointerException
                                                                               at com.example.amir.namaztimer.Slider_activity.onCreate(Slider_activity.java:26)
                                                                               at android.app.Activity.performCreate(Activity.java:5104)
                                                                               at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
                                                                               at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
                                                                               at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
                                                                               at android.app.ActivityThread.access$600(ActivityThread.java:141) 
                                                                               at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
                                                                               at android.os.Handler.dispatchMessage(Handler.java:99) 
                                                                               at android.os.Looper.loop(Looper.java:137) 
                                                                               at android.app.ActivityThread.main(ActivityThread.java:5041) 
                                                                               at java.lang.reflect.Method.invokeNative(Native Method) 
omer khan
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    Possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) – OneCricketeer May 08 '16 at 09:25
  • What is the code on line 26 in your SliderActivity? – Vucko May 08 '16 at 09:30
  • ` setPager();` it is function and body of function is ` viewPager = (ViewPager) findViewById(R.id.pagerr); FragmentManager fragmentManager = getSupportFragmentManager(); viewPager.setAdapter(new MyAdapter(fragmentManager)); ` – omer khan May 08 '16 at 09:53
  • Hint: `findViewById` returned null because you used the wrong xml in your setContentView. Or the id cannot be found in it. Please check both – OneCricketeer May 08 '16 at 09:56
  • {findViewById} is ok viewpager id same and setcontentview is calling slider_activity.xml...as i said code wase running ok but suddenly error appear... – omer khan May 08 '16 at 10:05
  • How did you solve it? – Martin De Simone Apr 15 '17 at 20:55
  • i posted the answer but they delete my answer never mind the solution was simple i just clean and rebuild the project – omer khan Apr 16 '17 at 18:22

1 Answers1

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If your xml name is silder.xml then you put the wrong xml in contentview.

Write :

setContentView(R.layout.silder);
Sayem
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