Intents in Jetpack

Intents in Android

An Intent is a messaging object in Android used to request actions from another app component (e.g., activity, service, broadcast receiver). It facilitates communication between components and is a key mechanism for enabling user navigation and inter-app communication.

Types of Intents

Explicit Intent: Directly specifies the target component (e.g., a specific activity or service).

Used within the same application.
Example: Launching a specific activity.

Implicit Intent: Does not specify the target component. The system determines the best component to handle the intent based on intent filters.

Used for actions like opening a webpage, sharing content, or making a call.

Key Components of an Intent

Action: Defines the general action to perform (e.g., ACTION_VIEW, ACTION_SEND).
Data: URI or MIME type specifying the data to act upon.
Category: Provides additional information about the component to be invoked.
Extras: Key-value pairs carrying additional data.
Flags: Instructions about how the activity should be launched (e.g., FLAG_ACTIVITY_NEW_TASK).

Explicit Intent Example

Launching Another Activity:

val intent = Intent(this, SecondActivity::class.java)
intent.putExtra("message", "Hello from MainActivity")
startActivity(intent)

Receiving Data in the Target Activity:

val message = intent.getStringExtra("message")
Log.d("SecondActivity", "Message received: $message")

Implicit Intent Example

Opening a Web Page:

val intent = Intent(Intent.ACTION_VIEW, Uri.parse("https://www.google.com"))
startActivity(intent)

Making a Phone Call:

val intent = Intent(Intent.ACTION_DIAL, Uri.parse("tel:+1234567890"))
startActivity(intent)

Sharing Content:

val intent = Intent(Intent.ACTION_SEND).apply {
    type = "text/plain"
    putExtra(Intent.EXTRA_TEXT, "Check out this awesome app!")
}
startActivity(Intent.createChooser(intent, "Share via"))

Intent Filters

An Intent Filter allows an activity, service, or broadcast receiver to declare which implicit intents it can handle.

Example: Manifest Declaration

<activity android:name=".MyActivity">
    <intent-filter>
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <data android:scheme="https" android:host="www.example.com" />
    </intent-filter>
</activity>

Intent Flags

Flags modify how intents behave when launching activities. Common flags include:

FLAG_ACTIVITY_NEW_TASK: Start a new task for the activity.
FLAG_ACTIVITY_CLEAR_TOP: Clear all activities above the target activity in the stack.
FLAG_ACTIVITY_SINGLE_TOP: Avoid launching a new instance if the activity is already on top.

Returning Results with Intents

Launching Activity for Result:

   val intent = Intent(this, SecondActivity::class.java)
   startActivityForResult(intent, REQUEST_CODE)

Returning Data from Target Activity:

   val intent = Intent()
   intent.putExtra("result", "Data from SecondActivity")
   setResult(RESULT_OK, intent)
   finish()

Receiving Results in the Caller Activity:

   override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
       super.onActivityResult(requestCode, resultCode, data)
       if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {
           val result = data?.getStringExtra("result")
           Log.d("MainActivity", "Result received: $result")
       }
   }

Broadcast Intents

Broadcast intents are sent to broadcast receivers to notify multiple components of a system-wide event.

Sending a Broadcast:

val intent = Intent("com.example.CUSTOM_ACTION")
intent.putExtra("key", "value")
sendBroadcast(intent)

Receiving a Broadcast:

class MyReceiver : BroadcastReceiver() {
    override fun onReceive(context: Context, intent: Intent) {
        val value = intent.getStringExtra("key")
        Log.d("MyReceiver", "Received: $value")
    }
}

Registering the Receiver:

In AndroidManifest.xml:

<receiver android:name=".MyReceiver">
    <intent-filter>
        <action android:name="com.example.CUSTOM_ACTION" />
    </intent-filter>
</receiver>

Best Practices

Security: Avoid exposing sensitive data with implicit intents.
Validation: Validate received data in the target component.
Optimization: Use explicit intents where possible for better performance and security.

ByRajashekar