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Mastering Android Mobile Applications: An In-Depth Study of Android Intents

Table of Contents

Introduction to Android Mobile Applications
Understanding Android Intents
Android Explicit Intents: A Comprehensive Study
Guided Lesson Activities for Android Explicit Intents
Worked Examples

Chapter 1: Introduction to Android Mobile Applications

This chapter provides an overview of Android mobile applications, their importance, and how they have revolutionized the digital world. It also touches upon basic concepts of Android programming.

Chapter 2: Understanding Android Intents

This chapter delves into the concept of Android Intents, their types, and how they facilitate communication between components in different applications.

Chapter 3: Android Explicit Intents: A Comprehensive Study

In this chapter, we delve deeper into the concept of explicit intents in Android. We'll explore what they are, how they work, and what makes them crucial in Android application development.

Chapter 4: Guided Lesson Activities for Android Explicit Intents

This chapter will guide you through hands-on activities that aim to strengthen your understanding and practical skills in working with explicit intents in Android.

Activity 1: Creating an Explicit Intent

Here, we will guide you through the process of creating an explicit intent to start a new activity.

Activity 2: Passing Data through Intent

In this activity, you will learn how to pass data from one activity to another using explicit intents.

Activity 3: Handling Result from an Intent

This activity aims to teach you how to handle results returned from an activity started by an intent.

Chapter 5: Worked Examples

This final chapter will provide three complete worked examples that incorporate everything you've learned about explicit intents in Android.

Example 1: Creating a Simple Calculator Application

In this example, we will create a simple calculator application that uses explicit intents to switch between different calculator modes.

Example 2: Creating a Multi-Screen Quiz Application

This example guides you through creating a quiz application that navigates across different screens using explicit intents.

Example 3: Creating a Note-Taking Application

In this final example, we will create a note-taking app that uses explicit intents to open a new page for each note created.
The book will include step-by-step instructions, screenshots, and detailed explanations of all code snippets used in the examples. It will also provide a comprehensive understanding of Android explicit intents, ensuring that by the end, students are well-equipped to incorporate this crucial aspect of Android development into their future projects.


Section 1: Overview of Android Mobile Applications

Android mobile applications have transformed the digital landscape by providing a platform for developers to create innovative and interactive mobile applications. These applications run on the Android operating system, which is an open-source platform developed by Google. Android applications are widely used on smartphones, tablets, smart TVs, and other devices.
Android applications offer a range of functionalities, including multimedia, internet browsing, gaming, social networking, and productivity tools. They provide a user-friendly interface and leverage the hardware capabilities of mobile devices, such as GPS, camera, accelerometer, and more. Android applications are typically developed using Java or Kotlin programming languages.

Section 2: Basic Concepts of Android Programming

To develop Android applications, developers need to understand some basic concepts of Android programming. Let's discuss the key concepts:
Activity: An activity represents a single screen with a user interface. It serves as the entry point for the user to interact with the application. Each activity has a lifecycle, consisting of methods like onCreate(), onStart(), onResume(), onPause(), onStop(), and onDestroy(), which define its behavior.
Layouts: Layouts define the structure and appearance of the user interface components within an activity. Android provides various layout types, such as LinearLayout, RelativeLayout, ConstraintLayout, and FrameLayout, which allow developers to organize the user interface elements effectively.
Views: Views are the building blocks of the user interface. They represent visual elements like buttons, text fields, images, and more. Android provides a wide range of pre-defined views, and developers can also create custom views to suit their application's specific needs.
Intents: Intents are messaging objects used to communicate between different components of an application, such as activities, services, and broadcast receivers. They enable actions like starting a new activity, launching a service, or broadcasting system-wide events.
Resources: Resources are external elements used in an application, such as strings, images, layouts, and dimensions. They are stored separately from the code and allow for easy localization and customization of the application.
Manifest File: The AndroidManifest.xml file contains essential information about the application, such as its package name, activities, services, permissions, and more. It acts as a configuration file for the application and is required for every Android project.

Section 3: Lab Workbook - Creating a Simple Android Application

In this lab workbook, we will create a simple Android application that displays a "Hello, Android!" message on the screen. We will use Android Studio, the official integrated development environment (IDE) for Android application development.
Step 1: Setting up the Development Environment
Download and install Android Studio from the official website ().
Launch Android Studio and set up the required SDKs and tools.
Step 2: Creating a New Project
Open Android Studio and click on "Start a new Android Studio project" or navigate to File -> New -> New Project.
Choose a project template (e.g., "Empty Activity") and click "Next."
Enter the application name, package name, and other details as per your preference.
Choose the minimum SDK version and click "Finish."
Step 3: Designing the User Interface
Open the activity_main.xml layout file located in the res/layout directory.
In the design view, drag and drop a TextView from the palette onto the layout.
Set the TextView's properties, such as text color, font size, and alignment, in the properties panel.
Set the text property of the TextView to "Hello, Android!"
Step 4: Writing the Kotlin Code
Open the MainActivity.kt file located in the java/<your_package_name> directory.
Replace the existing code with the following Kotlin code:
kotlinCopy code
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.TextView

class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val textView = findViewById<TextView>(R.id.textView)
textView.text = "Hello, Android!"
}
}

Step 5: Running the Application
Connect an Android device or set up an emulator in Android Studio.
Click on the "Run" button or press Shift + F10 to build and run the application.
The application will be installed and launched on the connected device or emulator, displaying the "Hello, Android!" message.


Understanding Android Intents

Example with Kotlin code:
kotlin
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val intent = Intent(this, SecondActivity::class.java)
startActivity(intent)

Android Explicit Intents

Here, we'll explore explicit intents in Android: what they are, how to use them, and when to use them.
Example with Kotlin code:
kotlin
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val intent = Intent(this, ExplicitActivity::class.java)
startActivity(intent)

Android Implicit Intents

***Learn about implicit intents in Android. We'll cover their uses and how to implement them in your application.
Example with Kotlin code:
kotlin
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val intent = Intent(Intent.ACTION_VIEW, Uri.parse("https://www.google.com"))
startActivity(intent)

Worked Examples

Here, we'll go through several examples of how to use Android Intents in real-world applications. We'll explain the code in detail to ensure you understand the concept.
Example with Kotlin code:
kotlin
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val intent = Intent(Intent.ACTION_SEND)
intent.type = "text/plain"
intent.putExtra(Intent.EXTRA_TEXT, "Hello, world!")
startActivity(Intent.createChooser(intent, "Share this message with..."))

Type out this program and get it to run: A complete Kotlin Android program that showcases both implicit and explicit intents:

KOTLIN CODE:
import android.content.Intent
import android.net.Uri
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Button

class MainActivity : AppCompatActivity(), View.OnClickListener {

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)

val implicitIntentButton: Button = findViewById(R.id.implicitIntentButton)
implicitIntentButton.setOnClickListener(this)

val explicitIntentButton: Button = findViewById(R.id.explicitIntentButton)
explicitIntentButton.setOnClickListener(this)
}

override fun onClick(view: View) {
when (view.id) {
R.id.implicitIntentButton -> {
val implicitIntent = Intent(Intent.ACTION_VIEW)
implicitIntent.data = Uri.parse("https://www.example.com")
startActivity(implicitIntent)
}
R.id.explicitIntentButton -> {
val explicitIntent = Intent(this, SecondActivity::class.java)
explicitIntent.putExtra("message", "Hello from MainActivity!")
startActivity(explicitIntent)
}
}
}
}

In this example, the MainActivity class extends AppCompatActivity and implements the View.OnClickListener interface. The activity layout file (activity_main.xml) should contain two buttons with the ids implicitIntentButton and explicitIntentButton.
The onCreate() method sets click listeners for both buttons, and the onClick() method handles the click events. When the implicitIntentButton is clicked, an implicit intent is created to open a web page (). This intent is then started using startActivity(), which launches a suitable activity to handle the intent.
When the explicitIntentButton is clicked, an explicit intent is created to navigate to the SecondActivity class. The intent includes an extra message ("Hello from MainActivity!") using the putExtra() method. The intent is then started, and the SecondActivity is launched.
Remember to create the SecondActivity class and define its layout file (activity_second.xml) to complete the program.

Here are some scenario-based program ideas that students can explore to illustrate the unique qualities and applications of implicit and explicit intents: You may choose to use some of these in your Project.
Music Player App:
Use an explicit intent to switch between different activities for play, pause, and stop functionalities.
Use an implicit intent to open the device's music player when a specific button is clicked.
Social Media Integration:
Use an implicit intent to share a message or image to various social media platforms.
Use an explicit intent to navigate to different activities representing different social media profiles.
Weather App:
Use an implicit intent to open a browser with a specific URL for weather details of a particular location.
Use an explicit intent to switch to a detailed weather activity when a specific location is selected.
Image Gallery:
Use an explicit intent to switch between activities for displaying different categories of images (e.g., nature, animals, etc.).
Use an implicit intent to allow the user to select an image from the gallery and display it in a specific activity.
Email Client:
Use an explicit intent to compose and send an email with predefined subject and content.
Use an implicit intent to open the default email client with predefined recipients and subject, allowing the user to compose the email.
Map Application:
Use an implicit intent to open a map application with a specific location marked.
Use an explicit intent to switch to a map activity where the user can search for a location and display it on the map.
Shopping App:
Use an explicit intent to switch between activities for browsing different categories of products.
Use an implicit intent to open a web browser with a specific product URL when the user clicks on a product.
Camera App:
Use an explicit intent to switch to a camera activity for capturing photos or videos.
Use an implicit intent to allow the user to select an image or video from the gallery and display it in a specific activity.
These scenarios provide opportunities for students to explore various applications of implicit and explicit intents in real-world contexts, enabling them to understand the flexibility and power of intents in Android app development.

For this next exercise, go to and get an API Key. Note that it will take 24 hours for your key to be fully registered, so you code will not work with the key until tomorrow.
image.png

Here's a complete Kotlin Android Weather App that utilizes the OpenWeather API to fetch weather data. It incorporates both an implicit intent to open a browser for weather details and an explicit intent to switch to a detailed weather activity when a location is selected. Please note that you'll need to obtain an API key from OpenWeather and replace "YOUR_API_KEY" with your actual API key in the code below:
MainActivity.kt:
kotlinCopy code
import android.content.Intent
import android.net.Uri
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity(), View.OnClickListener {

private lateinit var locationEditText: EditText

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)

val openBrowserButton: Button = findViewById(R.id.openBrowserButton)
openBrowserButton.setOnClickListener(this)

val showWeatherButton: Button = findViewById(R.id.showWeatherButton)
showWeatherButton.setOnClickListener(this)

locationEditText = findViewById(R.id.locationEditText)
}

override fun onClick(view: View) {
val location = locationEditText.text.toString()

when (view.id) {
R.id.openBrowserButton -> {
val url = "https://openweathermap.org/weather?q=$location"
val intent = Intent(Intent.ACTION_VIEW, Uri.parse(url))
startActivity(intent)
}
R.id.showWeatherButton -> {
val intent = Intent(this, WeatherActivity::class.java)
intent.putExtra("location", location)
startActivity(intent)
}
}
}
}

WeatherActivity.kt:
kotlinCopy code
import android.os.Bundle
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity

class WeatherActivity : AppCompatActivity() {

private lateinit var locationTextView: TextView

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_weather)

locationTextView = findViewById(R.id.locationTextView)

val location = intent.getStringExtra("location")
locationTextView.text = "Weather Details for $location"
}
}

activity_main.xml:
xmlCopy code
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="16dp">

<EditText
android:id="@+id/locationEditText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter Location" />

<Button
android:id="@+id/openBrowserButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Open Browser" />

<Button
android:id="@+id/showWeatherButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Show Weather" />

</LinearLayout>

activity_weather.xml:
xmlCopy code
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="16dp">

<TextView
android:id="@+id/locationTextView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="20sp"
android:textStyle="bold" />
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