why it gives me IllegalStateException when i click button on fragment

[shawn peter]

I have app with viewpager.I need to call other fragment methon when i click button on first fragment.

this is my mail Activity

package src.com.programmingmobile.pageviewer;

package src.com.programmingmobile.pageviewer;

import java.util.ArrayList;
import java.util.List;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.widget.Toast;

public class PageViewActivity extends FragmentActivity implements Communicator{
	MyPageAdapter pageAdapter;
    @Override
    public void onCreate(Bundle savedInstanceState) {
    	try{
        super.onCreate(savedInstanceState);
        
        setContentView(R.layout.activity_page_view);        
        List<Fragment> fragments = getFragments();        
        pageAdapter = new MyPageAdapter(getSupportFragmentManager(), fragments);        
        ViewPager pager = (ViewPager)findViewById(R.id.viewpager);
        pager.setAdapter(pageAdapter);
        
    	}catch(Exception e){
        	e.printStackTrace();
        }
        
    }
    
    private List<Fragment> getFragments(){
    	List<Fragment> fList = new ArrayList<Fragment>();
    	
    	fList.add(MyFragment.newInstance("Fragment 1"));
    	fList.add(MyFragment2.newInstance("Fragment 2"));
    	//fList.add(MyFragment.newInstance("Fragment 3"));
    	
    	return fList;
    }

    private class MyPageAdapter extends FragmentPagerAdapter {
    	
       	private List<Fragment> fragments;

        public MyPageAdapter(FragmentManager fm, List<Fragment> fragments) {
            super(fm);
            this.fragments = fragments;
        }
        @Override
        public Fragment getItem(int position) {
            return this.fragments.get(position);
        }
     
        @Override
        public int getCount() {
            return this.fragments.size();
        }
    }

	@Override
	public void respond(String data) {
		// TODO Auto-generated method stub
		MyFragment2 fragment = (MyFragment2) getSupportFragmentManager().findFragmentById(R.id.Fragment2); 
	    fragment.print();
		
	}
}

this is my fragment1

package src.com.programmingmobile.pageviewer;

import java.io.InputStream;

import javax.net.ssl.ManagerFactoryParameters;

import com.epapyrus.plugpdf.SimpleDocumentReader;
import com.epapyrus.plugpdf.SimpleDocumentReaderListener;
import com.epapyrus.plugpdf.SimpleReaderFactory;
import com.epapyrus.plugpdf.core.viewer.DocumentState;

import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.util.Log;
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 android.widget.TextView;

public class MyFragment extends Fragment{
	public static final String EXTRA_MESSAGE = "EXTRA_MESSAGE";

	Communicator com;

	public void onAttach(Activity a) {
		super.onAttach(a);
		com = (Communicator) a;
	}

	public static final MyFragment newInstance(String message) {
		MyFragment f = new MyFragment();
		Bundle bdl = new Bundle(1);
		bdl.putString(EXTRA_MESSAGE, message);
		f.setArguments(bdl);
		return f;
	}

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		String message = getArguments().getString(EXTRA_MESSAGE);
		View v = inflater.inflate(R.layout.myfragment_layout, container, false);
		TextView messageTextView = (TextView) v.findViewById(R.id.textView);
		messageTextView.setText(message);
		// OpenPdf();

		LinearLayout mLinearLayout = (LinearLayout) inflater.inflate(
				R.layout.myfragment_layout, container, false);

		// note that we're looking for a button with id="@+id/myButton" in your
		// inflated layout
		// Naturally, this can be any View; it doesn't have to be a button
		Button mButton = (Button) mLinearLayout.findViewById(R.id.button1);
		mButton.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				com.respond("Fragment ");
			}
		});

		return mLinearLayout;
	}

	

}

this is fragment2

package src.com.programmingmobile.pageviewer;

import java.io.InputStream;

import com.epapyrus.plugpdf.SimpleDocumentReader;
import com.epapyrus.plugpdf.SimpleDocumentReaderListener;
import com.epapyrus.plugpdf.SimpleReaderFactory;
import com.epapyrus.plugpdf.core.viewer.DocumentState;

import android.content.res.AssetManager;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MyFragment2 extends Fragment {
	public static final String EXTRA_MESSAGE = "EXTRA_MESSAGE";

	// create a listener for receiving provide pdf loading results
	SimpleDocumentReaderListener m_listener = new SimpleDocumentReaderListener() {

		@Override
		public void onLoadFinish(DocumentState.OPEN state) {
		}
	};

	public static final MyFragment2 newInstance(String message) {
		MyFragment2 f = new MyFragment2();
		Bundle bdl = new Bundle(1);
		bdl.putString(EXTRA_MESSAGE, message);
		f.setArguments(bdl);
		return f;
	}

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		String message = getArguments().getString(EXTRA_MESSAGE);
		View v = inflater.inflate(R.layout.myfragment_layout2, container, false);
		TextView messageTextView = (TextView) v.findViewById(R.id.textView);
		messageTextView.setText(message);
		//OpenPdf();
		return v;
	}

	public void print(){
		Toast.makeText(getActivity(), " inside Respond ", 100);
	}
	
}

this is myfragment_layout xml file

package src.com.programmingmobile.pageviewer;

import java.io.InputStream;

import javax.net.ssl.ManagerFactoryParameters;

import com.epapyrus.plugpdf.SimpleDocumentReader;
import com.epapyrus.plugpdf.SimpleDocumentReaderListener;
import com.epapyrus.plugpdf.SimpleReaderFactory;
import com.epapyrus.plugpdf.core.viewer.DocumentState;

import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class MyFragment extends Fragment {
	public static final String EXTRA_MESSAGE = "EXTRA_MESSAGE";

	Communicator com;

	public void onAttach(Activity a) {
		super.onAttach(a);
		com = (Communicator) com;
	}

	public static final MyFragment newInstance(String message) {
		MyFragment f = new MyFragment();
		Bundle bdl = new Bundle(1);
		bdl.putString(EXTRA_MESSAGE, message);
		f.setArguments(bdl);
		return f;
	}

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		String message = getArguments().getString(EXTRA_MESSAGE);
		View v = inflater.inflate(R.layout.myfragment_layout, container, false);
		TextView messageTextView = (TextView) v.findViewById(R.id.textView);
		messageTextView.setText(message);
		// OpenPdf();
		return v;
	}

	public void onclick(View v) {
		
		com.respond("Fragment ");
	}

}

this is my_fragment2 xml filee

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/Fragment2"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:textAppearance="?android:attr/textAppearanceLarge"/>

</RelativeLayout>

when i run the app it gives me the first fragment with a button.when i clcick button it gives me below error

10-07 09:37:52.610: E/AndroidRuntime(10907): FATAL EXCEPTION: main
10-07 09:37:52.610: E/AndroidRuntime(10907): java.lang.NullPointerException
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at src.com.programmingmobile.pageviewer.PageViewActivity.respond(PageViewActivity.java:66)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at src.com.programmingmobile.pageviewer.MyFragment$1.onClick(MyFragment.java:63)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at android.view.View.performClick(View.java:3620)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at android.view.View$PerformClick.run(View.java:14322)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at android.os.Handler.handleCallback(Handler.java:605)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at android.os.Handler.dispatchMessage(Handler.java:92)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at android.os.Looper.loop(Looper.java:137)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at android.app.ActivityThread.main(ActivityThread.java:4507)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at java.lang.reflect.Method.invokeNative(Native Method)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at java.lang.reflect.Method.invoke(Method.java:511)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:978)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:745)
10-07 09:37:52.610: E/AndroidRuntime(10907): 	at dalvik.system.NativeStart.main(Native Method)

The line which gives null pointer is below

MyFragment2 fragment = (MyFragment2) getSupportFragmentManager().findFragmentById(R.id.Fragment2); 

[Lakshan Dissanayake]

It seems like

getSupportFragmentManager()

is null.
It's bit hard to make a guess.
If you can send source code, I hope I'll be able to help you to solve this problem.
please check your private messages for my email address.

-Supun