Why different activities appear as separate application in android

Question

I am creating a Jigsaw Puzzle application in android. I have created two activites, activity_jigsaw.xml and activity_level.xml. One activity is created by default (Displaying Hello World!) which I modified and created a new activity by following these steps:

File -> New -> Other -> Android Activity

But when I install the application these two files (and all other activities of the application) are installed as a separate project. But at the same time they are also interlinked. The Java code of the files as follows:

Jisaw.java file contains:

public class Jigsaw extends Activity {

    Intent intent;

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_jigsaw, menu);
        return true;
    }

    public void play(View v)
    {
        try
        {
            intent = new Intent(this, Level.class);
            startActivity(intent);
        }

        catch(Exception e)
        {
            e.printStackTrace();
        }
    }
}

Here Play is a function which is called when an image is clicked.

Level.java file contains:

public class Level extends Activity {

    Intent intent;
    String level = "";

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_level, menu);
        return true;
    }

    public void easy(View v)
    {
        level = "easy";
        intent = new Intent(this, Play.class);
        intent.putExtra("level", level);
        startActivity(intent);
    }

    public void medium(View v)
    {
        level = "medium";
        intent = new Intent(this, Play.class);
        intent.putExtra("level", level);
        startActivity(intent);

    }

    public void hard(View v)
    {
        level = "hard";
        intent = new Intent(this, Play.class);
        intent.putExtra("level", level);
        startActivity(intent);

    }
}

Functions easy, medium and hard are called when a corresponding image is clicked.

Can somebody please tell me that what I am doing wrong?

Thanks in advance..

Here is the manifest file:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.maju.jigsawpuzzle"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="15" />

    <uses-permission android:name="android.permission.SET_WALLPAPER" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".Jigsaw"
            android:label="@string/title_activity_jigsaw" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Level"
            android:label="@string/title_activity_level" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Play"
            android:label="@string/title_activity_play" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".PlayBoard"
            android:label="@string/title_activity_play_board" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

Answer 1

You probably are defining android.intent.category.LAUNCHER intent category to all the activities in your AndroidManifest.xml, it creates an icon in the app launcher. Activities other than main should not have this intent filter.

Do something like this:

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
    <activity android:name=".JigSaw" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

EDIT: As you just posted, you are indeed doing that, just remove the intent filter from other activities.