In the below example I will discusss switching between activities in android. Here I have created two activities and named them Activity1 and Activity2 and used Intent and onclickListener in both activities. Also with I have created two xml layout, in both xml layout I have added one Textview and one button. See the below code example i have clearly describe you how to switch between Activities.

Step(1)-main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#ffffff"  >

    <TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:textColor="#000000"
    android:text="This is Activity 1" />

       <Button android:text="Next"
        android:id="@+id/Button01"
        android:layout_width="250px"
            android:textSize="18px"
        android:layout_height="55px">
    </Button>    

</LinearLayout>

Step(2)-Create main2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#ffffff"  >

    <TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:textColor="#000000"
    android:text="This is Activity 2" />

       <Button android:text="Previous"
        android:id="@+id/Button02"
        android:layout_width="250px"
            android:textSize="18px"
        android:layout_height="55px">
    </Button>    

</LinearLayout>

Step(3)-Add the second Activity to the main manifest file. Open AndroidManifest.xml and add:-

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.warriorpoint.taxman2"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Activity1"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".Activity2"></activity>
    </application>
    <uses-sdk android:minSdkVersion="3" />
</manifest>

Step(4)-Activity1-

public class Activity1 extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button next = (Button) findViewById(R.id.Button01);
        next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent myIntent = new Intent(view.getContext(), Activity2.class);
                startActivityForResult(myIntent, 0);
            }

        });
    }
}

Step(5)-Activity2-

public class Activity2 extends Activity {

    /** Called when the activity is first created. */
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main2);

        Button next = (Button) findViewById(R.id.Button02);
        next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent intent = new Intent();
                setResult(RESULT_OK, intent);
                finish();
            }

        });
    }