Not able to load intent from fragment on button click in android

Question

I have few fragments, in my android app, the fragments load fine, but i want to execute an intent by button click(the button is on one of the fragments).Here is the code.

MainActivity.java

public class MainActivity extends FragmentActivity{
ViewPager viewPager=null;
    Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        viewPager= (ViewPager) findViewById(R.id.pager);
        button = (Button) findViewById(R.id.button);

        // Capture button clicks
        button.setOnClickListener(new OnClickListener() {
            public void onClick(View arg0) {

                // Start NewActivity.class
                Intent myIntent = new Intent(MainActivity.this,eventload.class);
                startActivity(myIntent);
            }
        });
        FragmentManager fragmentManager=getSupportFragmentManager();
        viewPager.setAdapter(new MyAdapter(fragmentManager));
    }
}
class MyAdapter extends FragmentPagerAdapter
{
    public MyAdapter(FragmentManager fm) {
        super(fm);
        // TODO Auto-generated constructor stub
    }
    @Override
    public Fragment getItem(int i) {
        Fragment fragment = null;
        if (i==0)
        {
            fragment = new FragmentA();
        }
        if (i==1)
        {
            fragment = new FragmentB();
        }
        if (i==2)
        {
            fragment = new FragmentC();
        }


        return fragment;
    }

    @Override
    public int getCount() {

        return 3;
    }
    @Override
    public CharSequence getPageTitle(int position) {
        String title = new String();
        if (position==0)
        {
            return "Technical";
        }
        if (position==1)
        {
            return "Cultural";
        }
        if (position==2)
        {
            return "Sports";
        }


        return super.getPageTitle(position);
    }

}

Here is the eventload class

public class eventload extends Activity {

    Button button;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.load);
    }

}

Load.xml just has a radiobutton.

here is the manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.layouts"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity android:name=".MainActivity"></activity>
        <activity android:name=".eventload"></activity>
        <activity
            android:name=".SplashScreen"
            android:label="@string/app_name" >


            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

The app always crashes after displaying a splash screen(splash screen is not interfering here). And my logcat says

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.layouts/com.example.layouts.MainActivity}: java.lang.NullPointerException

I have mentioned MainActicity in the manifest.

Here is the activity main.xml

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"


    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" 
    android:background="@drawable/ic_launcher">
   <android.support.v4.view.PagerTitleStrip
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top"
        android:background="#33b5e5"
        android:paddingBottom="4dp"
        android:paddingTop="4dp"
        android:textColor="#fff" />


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

The button is in different fragment frag4.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.layouts.MainActivity$PlaceholderFragment" >

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/rounded_corner_box" >

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="See events"
            android:id="@+id/button"
            android:layout_gravity="left|top" />
    </FrameLayout>

</RelativeLayout>

FragmentC.java

 public class FragmentC  extends Fragment{
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            return inflater.inflate(R.layout.frag4,container,false);
        }
    }

Answer 1

You told button is on the fragment but you are instantiating the button in the activity which is not there in the activity. So it is getting NullPointerException. Instantiate the button in the fragment where the button is existed.

UPDATE1 Change your fragment onCreateView() method like this

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.frag4, container, false);
    Button button = (Button) view.findViewById(R.id.button);

    // Capture button clicks
    button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getActivity(), eventload.class);
            startActivity(myIntent);
        }
    });

    return view

Answer 2

Change the code of frag4 as following:

     public class FragmentC  extends Fragment{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
               View v = inflater.inflate(R.layout.frag4, container, false);
    // here v is the View you inflated from frag4.xml
    Button button = (Button) v.findViewById(R.id.button);

    // Capture button clicks
    button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getActivity(),eventload.class);
            startActivity(myIntent);
        }
    });
    return v;
    }
}

Answer 3

Pass getApplicationContext() as first parameter in when you create intent object.

Now your button.setOnClickListener() should look like

button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getApplicationContext(),eventload.class);
            startActivity(myIntent);
        }
    });