This tutorial helps you how to use Fragment Class in android Application

the sample code give you the brief on how you can use an fragment class. In main Activity we have created four fragments. And use FragmentManager and FragmentTransaction Class.

sample code: Create the main activity

package com.example.fragmentexample3;

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {
    int fragmentNo = 1;
    int counter = 1;
    FragmentManager fm;
    FragmentTransaction ft;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        fm = getFragmentManager();
        ft = fm.beginTransaction();
        /*
         * MyFragment fragment1 = new MyFragment();
         * 
         * MyDefaultFragment fragment2 = new MyDefaultFragment();
         * MyDefaultFragment fragment3 = new MyDefaultFragment();
         * MyDefaultFragment fragment4 = new MyDefaultFragment();
         */
        ft.replace(R.id.fragment1, new MyFragment());
        ft.replace(R.id.fragment2, new MyDefaultFragment());
        ft.replace(R.id.fragment3, new MyDefaultFragment());
        ft.replace(R.id.fragment4, new MyDefaultFragment());
        // fragment2.onCreateView(getLayoutInflater(),(FrameLayout)findViewById(R.id.fragment2),
        // savedInstanceState);
        ft.commit();
        Button b = (Button) findViewById(R.id.button1);
        b.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                fm = getFragmentManager();
                ft = fm.beginTransaction();
                counter++;
                if (counter > 4)
                    counter = 1;
                System.out.println("counter" + counter);
                if (counter == 1) {
                    System.out.println("in counter 1");
                    ft.replace(R.id.fragment1, new MyFragment());
                    ft.replace(R.id.fragment2, new MyDefaultFragment());
                    ft.replace(R.id.fragment4, new MyDefaultFragment());

                } else if (counter == 2) {
                    System.out.println("in counter 2");
                    ft.replace(R.id.fragment1, new MyDefaultFragment());
                    ft.replace(R.id.fragment2, new MyFragment());

                } else if (counter == 3) {
                    System.out.println("in counter 3");

                    ft.replace(R.id.fragment2, new MyDefaultFragment());
                    ft.replace(R.id.fragment3, new MyFragment());

                } else if (counter == 4) {
                    System.out.println("in counter 4");
                    ft.replace(R.id.fragment3, new MyDefaultFragment());
                    ft.replace(R.id.fragment4, new MyFragment());
                }
                ft.commit();
            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

Then set Layout for MainActivity main_activity.xml

<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="14dp"
    android:text="Change" />

<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentRight="true"
    android:layout_below="@+id/button1"
    android:orientation="vertical" >

    <FrameLayout
        android:id="@+id/fragment1"
        android:layout_width="match_parent"
        android:layout_height="75dp"
        android:layout_marginTop="50dp" >
    </FrameLayout>

    <FrameLayout
        android:id="@+id/fragment2"
        android:layout_width="match_parent"
        android:layout_height="75dp"
        android:layout_marginTop="10dp" >
    </FrameLayout>

    <FrameLayout
        android:id="@+id/fragment3"
        android:layout_width="match_parent"
        android:layout_height="75dp"
        android:layout_marginTop="10dp" >
    </FrameLayout>

    <FrameLayout
        android:id="@+id/fragment4"
        android:layout_width="match_parent"
        android:layout_height="75dp"
        android:layout_marginTop="10dp" >
    </FrameLayout>
</LinearLayout>

Create the two fragment Class:: MyFragment.java And MyDefaultFragment.java

MyFragment.java

package com.example.fragmentexample3;

import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class MyFragment extends Fragment {
    MainActivity mainAvtivity;
    View view;

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

        view = inflater.inflate(R.layout.fragmentlayout, container, false);
        return view;

    }
}

MyDefaultFragment.java

package com.example.fragmentexample3;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class MyDefaultFragment extends Fragment {
    View view;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        view=inflater.inflate(R.layout.defaltfragmentlayout,container,false);
        return view;
    }

}