Android Development: Intents

In the world of Android, an Intent is essentially an “intention” to do something. Think of it as a messenger that carries instructions from one component to another.

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1. Explicit Intents: Navigating Your App

Explicit intents are used when you know exactly which component you want to start (usually another Activity within your own app). It’s like calling a friend by their full name.

The XML (activity_main.xml)

You’ll need a trigger, like a button:

XML

<Button
    android:id="@+id/btnNavigate"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Go to Second Screen" />

The Kotlin Logic

Inside your MainActivity.kt:

Kotlin

val intent = Intent(this, SecondActivity::class.java)
// Optional: Pass data to the next screen
intent.putExtra("USER_NAME", "Alex") 
startActivity(intent)

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2. Implicit Intents: Using System Apps

Implicit intents don’t name a specific component. Instead, they declare a general action (like “take a photo” or “send an email”) and let the Android system find the best app to handle it.

A. Make a Phone Call

This opens the dialer with the number pre-filled.

Kotlin

val dialIntent = Intent(Intent.ACTION_DIAL).apply {
    data = Uri.parse("tel:1234567890")
}
startActivity(dialIntent)

B. Send an SMS

Kotlin

val smsIntent = Intent(Intent.ACTION_SENDTO).apply {
    data = Uri.parse("smsto:1234567890")
    putExtra("sms_body", "Hey, check out this Android Intent!")
}
startActivity(smsIntent)

C. Send an Email

Emails require a bit more detail to ensure only email apps respond.

Kotlin

val emailIntent = Intent(Intent.ACTION_SEND).apply {
    type = "text/plain"
    putExtra(Intent.EXTRA_EMAIL, arrayOf("recipient@example.com"))
    putExtra(Intent.EXTRA_SUBJECT, "Hello from Kotlin")
    putExtra(Intent.EXTRA_TEXT, "This is an implicit intent test.")
}
if (emailIntent.resolveActivity(packageManager) != null) {
    startActivity(emailIntent)
}

D. Open the Camera

To simply capture a photo and return it:

Kotlin

val cameraIntent = Intent(MediaStore.ACTION_IMAGE_CAPTURE)
// Note: In modern Android, you'll need to handle URI permissions for the file
startActivity(cameraIntent)

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Summary Table

Intent Type	Use Case	Key Characteristic
Explicit	Switching between ActivityA and ActivityB.	You define the exact class name.
Implicit	Opening a URL, calling, or taking a photo.	You define the Action (e.g., ACTION_VIEW).