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Q-3: Intents in Android OR Toolbar in Android (5 Marks)

Questions​

a) What are Intents in Android, and how are they used? (5 marks)

OR

b) What is the Toolbar in Android, and how is it used? (5 marks)

Answers​

a) Intents in Android and their Usage​

Definition​

Intent is a messaging object that facilitates communication between different components of an Android application or between different applications.

Purpose​

Intents serve as a bridge for:

  • Component Communication: Connect activities, services, broadcast receivers
  • Data Transfer: Pass data between components
  • Action Requests: Request specific actions from other components
  • Application Integration: Enable inter-app communication

Types of Intents​

1. Explicit Intents

  • Definition: Specify the exact component to be invoked
  • Usage: Navigation within the same application
  • Target: Known component (activity, service)

Example:

Intent explicitIntent = new Intent(MainActivity.this, SecondActivity.class);
explicitIntent.putExtra("message", "Hello from MainActivity");
startActivity(explicitIntent);

2. Implicit Intents

  • Definition: Don't specify exact component, but declare action to be performed
  • Usage: Request actions from other apps or system
  • Target: Any component that can handle the action

Example:

// Open web browser
Intent webIntent = new Intent(Intent.ACTION_VIEW);
webIntent.setData(Uri.parse("https://www.google.com"));
startActivity(webIntent);

// Send email
Intent emailIntent = new Intent(Intent.ACTION_SEND);
emailIntent.setType("text/plain");
emailIntent.putExtra(Intent.EXTRA_EMAIL, new String[]{"test@example.com"});
emailIntent.putExtra(Intent.EXTRA_SUBJECT, "Subject");
startActivity(emailIntent);

Common Intent Actions​

  • ACTION_VIEW: Display data to user
  • ACTION_SEND: Share data with other apps
  • ACTION_CALL: Make phone call
  • ACTION_DIAL: Open dialer with number
  • ACTION_EDIT: Edit data
  • ACTION_PICK: Select item from data

Data Transfer with Intents​

// Sending data
Intent intent = new Intent(this, TargetActivity.class);
intent.putExtra("key1", "value1");
intent.putExtra("key2", 123);
startActivity(intent);

// Receiving data
Intent receivedIntent = getIntent();
String value1 = receivedIntent.getStringExtra("key1");
int value2 = receivedIntent.getIntExtra("key2", 0);

Intent Filters​

  • Purpose: Declare what kinds of intents a component can handle
  • Location: Defined in AndroidManifest.xml
  • Components: Action, data, category

Example:

<activity android:name=".MyActivity">
    <intent-filter>
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <data android:scheme="http" />
    </intent-filter>
</activity>

b) Toolbar in Android and its Usage​

Definition​

Toolbar is a flexible widget that serves as a replacement for the traditional ActionBar, providing a more customizable and material design-compliant app bar.

Key Features​

  • Material Design: Follows Material Design guidelines
  • Customization: Highly customizable appearance and behavior
  • Flexibility: Can be placed anywhere in the layout
  • Backwards Compatibility: Works with older Android versions through AppCompat

Setting up Toolbar​

1. Add to Layout:

<androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:elevation="4dp"
    android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

2. Setup in Activity:

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        
        // Optional: Enable up button
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setTitle("My App");
    }
}

Toolbar Components​

1. Navigation Icon

toolbar.setNavigationIcon(R.drawable.ic_menu);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        // Handle navigation click
    }
});

2. Title and Subtitle

toolbar.setTitle("Main Title");
toolbar.setSubtitle("Subtitle");

3. Menu Items

  • Create menu resource file (res/menu/toolbar_menu.xml):
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    
    <item
        android:id="@+id/action_search"
        android:icon="@drawable/ic_search"
        android:title="Search"
        app:showAsAction="ifRoom" />
        
    <item
        android:id="@+id/action_settings"
        android:title="Settings"
        app:showAsAction="never" />
</menu>
  • Handle menu events:
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.toolbar_menu, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.action_search:
            // Handle search
            return true;
        case R.id.action_settings:
            // Handle settings
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

Customization Options​

  • Colors: Background, text, icon colors
  • Typography: Font, text size, style
  • Layout: Height, padding, margins
  • Elevation: Shadow depth
  • Animation: Scroll behavior, transitions

Best Practices​

  • Consistent Design: Follow Material Design guidelines
  • Important Actions: Place primary actions as icons
  • Overflow Menu: Use for secondary actions
  • Navigation: Provide clear navigation cues
  • Responsive: Adapt to different screen sizes