Q-4: LinearLayout vs RelativeLayout OR Context Menu Implementation (5 Marks)

Questions

i) Design a user interface using LinearLayout and RelativeLayout. Explain the difference between them.

ii) Implement a context menu in an Android application and demonstrate its functionality.

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Answers

i) LinearLayout vs RelativeLayout Design and Differences

LinearLayout Design Example

<!-- LinearLayout Example: Vertical Login Form -->
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    android:gravity="center">
    
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Login Form"
        android:textSize="24sp"
        android:textStyle="bold"
        android:layout_marginBottom="32dp" />
    
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Username"
        android:layout_marginBottom="16dp" />
    
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Password"
        android:inputType="textPassword"
        android:layout_marginBottom="24dp" />
    
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:gravity="center">
        
        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Login"
            android:layout_marginEnd="8dp" />
        
        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Cancel"
            android:layout_marginStart="8dp" />
    </LinearLayout>
</LinearLayout>

RelativeLayout Design Example

<!-- RelativeLayout Example: Profile Layout -->
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp">
    
    <ImageView
        android:id="@+id/profileImage"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:layout_centerHorizontal="true"
        android:layout_alignParentTop="true"
        android:src="@drawable/ic_profile"
        android:layout_marginTop="32dp" />
    
    <TextView
        android:id="@+id/nameText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/profileImage"
        android:layout_centerHorizontal="true"
        android:text="John Doe"
        android:textSize="20sp"
        android:textStyle="bold"
        android:layout_marginTop="16dp" />
    
    <TextView
        android:id="@+id/emailText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/nameText"
        android:layout_centerHorizontal="true"
        android:text="john@example.com"
        android:layout_marginTop="8dp" />
    
    <Button
        android:id="@+id/editButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/emailText"
        android:layout_alignParentStart="true"
        android:text="Edit Profile"
        android:layout_marginTop="32dp" />
    
    <Button
        android:id="@+id/logoutButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/emailText"
        android:layout_alignParentEnd="true"
        android:text="Logout"
        android:layout_marginTop="32dp" />
    
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="Version 1.0"
        android:textSize="12sp"
        android:layout_marginBottom="16dp" />
</RelativeLayout>

Key Differences

Aspect	LinearLayout	RelativeLayout
Organization	Sequential (linear) arrangement	Relative positioning to other views
Orientation	Horizontal or Vertical	No specific orientation
Positioning	Based on order in XML	Based on relationship rules
Flexibility	Limited positioning options	Highly flexible positioning
Performance	Better performance	Slower due to multiple measurement passes
Nesting	Often requires nesting for complex layouts	Can achieve complex layouts without nesting
Use Case	Simple, sequential layouts	Complex, overlapping layouts

Positioning Attributes

LinearLayout:

• android:orientation: vertical/horizontal
• android:layout_weight: distribute space proportionally
• android:gravity: align children within the layout
• android:layout_gravity: align view within parent

RelativeLayout:

• android:layout_above: position above another view
• android:layout_below: position below another view
• android:layout_toLeftOf: position to left of another view
• android:layout_toRightOf: position to right of another view
• android:layout_alignParentTop: align to parent's top
• android:layout_centerInParent: center in parent

---

ii) Context Menu Implementation

Step 1: Register View for Context Menu

public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private ArrayAdapter<String> adapter;
    private List<String> items;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        listView = findViewById(R.id.listView);
        items = new ArrayList<>();
        items.add("Item 1");
        items.add("Item 2");
        items.add("Item 3");
        
        adapter = new ArrayAdapter<>(this, 
            android.R.layout.simple_list_item_1, items);
        listView.setAdapter(adapter);
        
        // Register for context menu
        registerForContextMenu(listView);
    }
}

Step 2: Create Context Menu

@Override
public void onCreateContextMenu(ContextMenu menu, View v, 
        ContextMenu.ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu, v, menuInfo);
    
    // Inflate menu from XML
    getMenuInflater().inflate(R.menu.context_menu, menu);
    
    // Or create programmatically
    menu.setHeaderTitle("Select Action");
    menu.add(0, 1, 0, "Edit");
    menu.add(0, 2, 0, "Delete");
    menu.add(0, 3, 0, "Share");
}

Step 3: Create Menu Resource File

res/menu/context_menu.xml:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/menu_edit"
        android:title="Edit" />
    <item
        android:id="@+id/menu_delete"
        android:title="Delete" />
    <item
        android:id="@+id/menu_share"
        android:title="Share" />
    <item
        android:id="@+id/menu_copy"
        android:title="Copy" />
</menu>

Step 4: Handle Menu Item Selection

@Override
public boolean onContextItemSelected(MenuItem item) {
    AdapterView.AdapterContextMenuInfo info = 
        (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
    int position = info.position;
    String selectedItem = items.get(position);
    
    switch (item.getItemId()) {
        case R.id.menu_edit:
            editItem(position, selectedItem);
            return true;
            
        case R.id.menu_delete:
            deleteItem(position);
            return true;
            
        case R.id.menu_share:
            shareItem(selectedItem);
            return true;
            
        case R.id.menu_copy:
            copyItem(selectedItem);
            return true;
            
        default:
            return super.onContextItemSelected(item);
    }
}

Step 5: Implement Action Methods

private void editItem(int position, String item) {
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Edit Item");
    
    final EditText input = new EditText(this);
    input.setText(item);
    builder.setView(input);
    
    builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            String newText = input.getText().toString();
            items.set(position, newText);
            adapter.notifyDataSetChanged();
        }
    });
    
    builder.setNegativeButton("Cancel", null);
    builder.show();
}

private void deleteItem(int position) {
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Delete Item")
           .setMessage("Are you sure you want to delete this item?")
           .setPositiveButton("Delete", new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int which) {
                   items.remove(position);
                   adapter.notifyDataSetChanged();
               }
           })
           .setNegativeButton("Cancel", null)
           .show();
}

private void shareItem(String item) {
    Intent shareIntent = new Intent(Intent.ACTION_SEND);
    shareIntent.setType("text/plain");
    shareIntent.putExtra(Intent.EXTRA_TEXT, item);
    startActivity(Intent.createChooser(shareIntent, "Share via"));
}

private void copyItem(String item) {
    ClipboardManager clipboard = (ClipboardManager) 
        getSystemService(CLIPBOARD_SERVICE);
    ClipData clip = ClipData.newPlainText("Copied Item", item);
    clipboard.setPrimaryClip(clip);
    
    Toast.makeText(this, "Item copied to clipboard", Toast.LENGTH_SHORT).show();
}

Alternative: Floating Context Menu

// For floating context menu (older approach)
public void showContextMenu(View view) {
    PopupMenu popup = new PopupMenu(this, view);
    popup.getMenuInflater().inflate(R.menu.context_menu, popup.getMenu());
    
    popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
        @Override
        public boolean onMenuItemClick(MenuItem item) {
            // Handle menu item clicks
            return true;
        }
    });
    
    popup.show();
}

Benefits of Context Menus

• Space Efficiency: Don't take permanent screen space
• Contextual Actions: Actions relevant to selected item
• User Experience: Familiar interaction pattern
• Accessibility: Support for different interaction methods