Q-3: Attempt the following (Any two) (10 Marks)

Questions

A: Differentiate between DVM and JVM.
B: State syntax to create Text View and Image button with any two attributes of each.
C: Describe Android service life cycle along with diagram.

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Answer A: Differentiate between DVM and JVM

Aspect	DVM (Dalvik Virtual Machine)	JVM (Java Virtual Machine)
Full Form	Dalvik Virtual Machine	Java Virtual Machine
Architecture	Register-based	Stack-based
File Format	.dex (Dalvik Executable)	.class files
Memory Usage	Less memory consumption	More memory consumption
Performance	Faster execution	Slower compared to DVM
Platform	Android specific	Platform independent
Optimization	Optimized for mobile devices	General purpose optimization
Multiple Instances	Multiple DVM instances can run	Single JVM instance per application
Bytecode	Dalvik bytecode (.dex)	Java bytecode (.class)
Garbage Collection	Concurrent garbage collector	Various GC algorithms
Purpose	Mobile application execution	Desktop/server applications
Resource Constraints	Designed for limited resources	Not specifically resource-constrained

Key Differences:

1. DVM uses register-based architecture making it more efficient for mobile devices
2. JVM uses stack-based architecture which is more traditional
3. DVM runs .dex files while JVM runs .class files
4. DVM is optimized for Android while JVM is platform-independent

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Answer B: Syntax for TextView and ImageButton

TextView Syntax with Attributes

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World"
    android:textSize="18sp"
    android:textColor="#000000"
    android:background="#FFFFFF"
    android:padding="10dp"
    android:gravity="center" />

Two Key Attributes for TextView:

1. android:text - Sets the text content to display
2. android:textSize - Sets the size of the text (in sp units)

ImageButton Syntax with Attributes

<ImageButton
    android:id="@+id/imageButton1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/ic_button"
    android:background="@drawable/button_background"
    android:contentDescription="Image Button"
    android:scaleType="fitCenter"
    android:padding="8dp"
    android:onClick="imageButtonClick" />

Two Key Attributes for ImageButton:

1. android:src - Sets the image/icon to display on the button
2. android:background - Sets the background drawable or color for the button

Additional Common Attributes:

• android:id - Unique identifier
• android:layout_width/height - Dimensions
• android:onClick - Click event handler
• android:padding - Internal spacing

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Answer C: Android Service Life Cycle with Diagram

Android Service Life Cycle

A service is a component that runs in the background to perform long-running operations without user interface.

Service Life Cycle Methods:

1. onCreate() - Called when service is first created
2. onStartCommand() - Called when service is started using startService()
3. onBind() - Called when service is bound using bindService()
4. onUnbind() - Called when all clients unbind from service
5. onRebind() - Called when service is rebound after unbinding
6. onDestroy() - Called when service is destroyed

Service Life Cycle Diagram:

    Service Created
          |
      onCreate()
          |
    ┌─────────────────┐
    │                 │
    ▼                 ▼
startService()    bindService()
    │                 │
    ▼                 ▼
onStartCommand()   onBind()
    │                 │
    ▼                 │
Service Running       │
    │                 │
    ▼                 ▼
stopService()     unbindService()
    │                 │
    ▼                 ▼
Service Stopped    onUnbind()
    │                 │
    └─────────┬───────┘
              ▼
          onDestroy()
              │
              ▼
        Service Destroyed

Types of Services:

1. Started Service (using startService())

   • Runs indefinitely in background
   • Must stop itself or be stopped by another component

2. Bound Service (using bindService())

   • Provides client-server interface
   • Runs only while bound to components

Service States:

• Created: Service object created but not running
• Started: Service running after startService() call
• Bound: Service bound to client components
• Destroyed: Service stopped and resources released

Example Service Implementation:

public class MyService extends Service {
    
    @Override
    public void onCreate() {
        super.onCreate();
        // Initialize service
    }
    
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // Service logic here
        return START_STICKY; // Restart if killed
    }
    
    @Override
    public IBinder onBind(Intent intent) {
        return null; // Return null for started service
    }
    
    @Override
    public void onDestroy() {
        super.onDestroy();
        // Cleanup resources
    }
}

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