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POStarting Activity from Fragment causes NullPointerException
 

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    <p>I'm stuck here with a problem starting an activity from a Button inside a Fragment. Here is my code:</p> <p><strong>ViewPagerAdapter.java</strong></p> <pre><code>import java.util.List; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentManager; import android.support.v4.app.FragmentPagerAdapter; public class ViewPagerAdapter extends FragmentPagerAdapter { private List&lt;Fragment&gt; fragments; public ViewPagerAdapter(FragmentManager fm, List&lt;Fragment&gt; fragments) { super(fm); this.fragments = fragments; } @Override public int getCount() { return this.fragments.size(); } @Override public Fragment getItem(int position) { return this.fragments.get(position); } } </code></pre> <p><strong>ViewPagerActivity.java</strong></p> <pre><code>import java.util.List; import java.util.Vector; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentActivity; import android.support.v4.view.ViewPager; import android.util.Log; import com.package.here.Class1Overview; import com.package.here.Class1Overview; import com.package.here.Class1Overview; public class ViewPagerActivity extends FragmentActivity{ @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); super.setContentView(R.layout.viewpager); ViewPager pager = (ViewPager)super.findViewById(R.id.my_viewpager); pager.setAdapter(initialisePaging()); } private ViewPagerAdapter initialisePaging() { List&lt;Fragment&gt; fragments = new Vector&lt;Fragment&gt;(); fragments.add(Fragment.instantiate(this, Class1Overview.class.getName())); fragments.add(Fragment.instantiate(this, Class2Overview.class.getName())); fragments.add(Fragment.instantiate(this, Class3Overview.class.getName())); return new ViewPagerAdapter(super.getSupportFragmentManager(), fragments); } } </code></pre> <p><strong>Class1Overview.java</strong> (Here is the button)</p> <pre><code>import android.content.Intent; import android.os.Bundle; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.View.OnClickListener; import android.view.ViewGroup; import android.widget.Button; import android.widget.LinearLayout; import com.package.here.R; public class FuelOverview extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { if (container == null) { return null; } View v = (LinearLayout)inflater.inflate(R.layout.class_one_layout, container, false); View AddBtn = v.findViewById(R.id.btn_add); ((Button) AddBtn).setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent(); intent.setClass(getActivity(), ActivityToStart.class); startActivity(intent); } }); return v; } } </code></pre> <p>And this is my <strong>LogCat</strong>:</p> <pre><code>01-05 19:39:00.913: E/AndroidRuntime(10557): Uncaught handler: thread main exiting due to uncaught exception 01-05 19:39:01.034: E/AndroidRuntime(10557): java.lang.RuntimeException: Unable to pause activity {com.package.here/com.package.here.ViewPagerActivity}: java.lang.NullPointerException 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3162) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3119) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:3102) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.ActivityThread.access$2400(ActivityThread.java:119) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1870) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.os.Handler.dispatchMessage(Handler.java:99) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.os.Looper.loop(Looper.java:123) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.ActivityThread.main(ActivityThread.java:4363) 01-05 19:39:01.034: E/AndroidRuntime(10557): at java.lang.reflect.Method.invokeNative(Native Method) 01-05 19:39:01.034: E/AndroidRuntime(10557): at java.lang.reflect.Method.invoke(Method.java:521) 01-05 19:39:01.034: E/AndroidRuntime(10557): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 01-05 19:39:01.034: E/AndroidRuntime(10557): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 01-05 19:39:01.034: E/AndroidRuntime(10557): at dalvik.system.NativeStart.main(Native Method) 01-05 19:39:01.034: E/AndroidRuntime(10557): Caused by: java.lang.NullPointerException 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.support.v4.app.FragmentManagerImpl.saveFragmentBasicState(FragmentManager.java:1576) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.support.v4.app.FragmentManagerImpl.saveAllState(FragmentManager.java:1617) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.support.v4.app.FragmentActivity.onSaveInstanceState(FragmentActivity.java:481) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.Activity.performSaveInstanceState(Activity.java:1022) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.Instrumentation.callActivityOnSaveInstanceState(Instrumentation.java:1180) 01-05 19:39:01.034: E/AndroidRuntime(10557): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3144) 01-05 19:39:01.034: E/AndroidRuntime(10557): ... 12 more 01-05 19:39:01.423: I/dalvikvm(10557): threadid=7: reacting to signal 3 </code></pre> <p>ViewPager itself is working fine. It seems to be an error pausing the FragmentActivity, but i can't figure it out. The only thing I found was this post on google <a href="http://code.google.com/p/android/issues/detail?id=19917" rel="noreferrer">http://code.google.com/p/android/issues/detail?id=19917</a> </p> <p>I also got through the google example code to make sure I mainly use the same technique...</p> <p>Edit: to make sure the ClickListener works, I tried a Toast in the onClick method - works perfectly.</p>
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    1. COJust figured out the following: FragmentActivity crashes when: - pressing home button - turning the orientation of the device - starting an Avtivity - calling finish works fine So for the moment this works for me: Overwrite the onSaveInstanceState method without calling the super method and you're fine. Except for the fact, that the instance state isn't saved :D So this is not really a fix, but may nail down the problem.
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    2. COI just had the same problem - the issue for me was caused when I added a new fragment to my project with an empty layout. It seems that somewhere in the code, if nothing is saved to the bundle during onSaveInstanceState it must cause a null pointer exception. Adding some views to my layouts fixed the issue (after hours spent bashing my head against a wall). I am using android support library v4 revision 10.
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    3. CO@Juke Is it possible to get same behaviour of TabViewActivity using fragmentation, I want to open a new activity in fragmentation area on selectyion od any tab?
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