Intent

In Android development, Intents are a crucial mechanism for communication between different components of an app, such as Activities, Services, and Broadcast Receivers. They essentially represent a message that an app component sends to another component.

Types of Intents:

1. Explicit Intents:
   
   

   • Directly specify the target component by its class name.

   • Used for communication within your app.

   • Example:

// Java

Intent intent = new Intent(this, SecondActivity.class);

startActivity(intent);

2. Implicit Intents:

• Define the action to be performed and the data to be used.

• The system finds the appropriate component to handle the intent based on intent filters.

• Used for system actions or invoking other apps.

• Example:

// Java

Intent intent = new Intent(Intent.ACTION_VIEW);

intent.setData(Uri.parse("https://www.google.com"));

startActivity(intent);

Key Components of an Intent:

• Action: Specifies the action to be performed (e.g., ACTION_VIEW, ACTION_SEND).

• Data: Specifies the data to be used for the action (e.g., a URI, a file path).

• Category: Specifies additional information about the intent (e.g., CATEGORY_DEFAULT, CATEGORY_BROWSABLE).

• Extras: Additional data that can be passed with the intent (e.g., key-value pairs).

Common Use Cases:

• Starting Activities: Launch new activities within your app or other apps.

• Sending Data Between Activities: Pass data using extras.

• Invoking System Services: Use implicit intents to trigger system actions like making calls, sending emails, or opening maps.

• Receiving Broadcasts: Register Broadcast Receivers to listen for system-wide events or custom broadcasts.

Example: Starting a New Activity and Passing Data

Java

// In MainActivity:

Intent intent = new Intent(this, SecondActivity.class);

intent.putExtra("message", "Hello from MainActivity");

startActivity(intent);

// In SecondActivity:

Intent intent = getIntent();

String message = intent.getStringExtra("message");

// Use the received message

Intent Filters:

Intent filters are used to declare which implicit intents an app component can handle. They are defined in the AndroidManifest.xml file.

XML

<activity android:name=".SecondActivity">

    <intent-filter>

        <action android:name="android.intent.action.VIEW" />

        <category android:name="android.intent.category.DEFAULT"  

/>

        <data android:scheme="http" android:host="www.example.com" />

    </intent-filter>

</activity>