Android Applications Basics

👉 Overview

👀 What ?

Android applications are software applications designed to run on the Android operating system, which is primarily used in mobile devices. The basic fundamental concepts of Android applications include the Android Software Development Kit (SDK), Android activity lifecycle, Android services, and the Android Manifest file.

🧐 Why ?

Android applications are a critical component of the Android ecosystem, making the understanding of their basics important. They solve a range of problems from communication to entertainment, and business operations. With billions of Android users worldwide, understanding the basics of Android applications can open doors to vast opportunities, from app development to cybersecurity.

⛏️ How ?

To use the basics of Android applications to your advantage, you would need to understand the Android SDK, which provides the libraries and tools needed for development. The Android activity lifecycle, which is crucial for creating user interfaces and managing their interactions, is another critical component. Services, which run in the background, are necessary for tasks like playing music or downloading files. Lastly, the Android Manifest file, which declares app components and permissions, is fundamental for any Android app.

⏳ When ?

The basics of Android applications have been in use since the launch of the Android platform by Google in 2007. Over the years, they have continued to evolve, with new features and enhancements.

⚙️ Technical Explanations

Android applications, designed to run on the Android operating system, are integral to the Android ecosystem and have vast opportunities for developers. Understanding their basics is crucial for creating efficient and effective apps.

The Android Software Development Kit (SDK) is a comprehensive suite of development tools provided by Google, encompassing libraries for interface components, data management, network communication, and much more. These libraries and tools allow developers to build, test, and debug apps for Android.

The Android activity lifecycle is a fundamental concept in Android app development. It refers to the series of states that a single screen (activity) in an app goes through from creation to destruction, including states like "started", "paused", "resumed", and "stopped". Understanding this lifecycle is essential for managing resources effectively, ensuring app stability, and providing a smooth user experience.

Android services are another core component of Android apps. They are used for long-running operations or tasks that need to be performed even when the user is not interacting with the app. Services run in the background, independent of any user interface, and thus allow tasks to proceed without interrupting the user experience.

Lastly, the Android Manifest file is an XML file in every Android project that declares the app's components, such as activities, services, broadcast receivers, and content providers. It also specifies required system features, permissions, and linked libraries. This file is the essential blueprint for how the app interacts with the Android system and the user's device.

In summary, to develop Android applications effectively and securely, it's crucial to understand these fundamental concepts: the Android SDK, the activity lifecycle, services, and the Android Manifest file. It's these components that together create the robust and dynamic nature of Android applications.

Let's illustrate these concepts with a simple example: a basic Android app that displays a message when a button is clicked.

1. Android SDK: To begin with, we need the Android SDK. This can be installed through the Android Studio IDE. Once installed, we can create a new project and select the appropriate SDK for our app.

import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {

    Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.buttonToast);
    }
}

2. Android Activity Lifecycle: Our app currently has one activity: MainActivity. This activity goes through different lifecycle states.

@Override
protected void onStart() {
    super.onStart();
    // The activity is about to become visible.
}

@Override
protected void onResume() {
    super.onResume();
    // The activity has become visible (it is now "resumed").
}

@Override
protected void onPause() {
    super.onPause();
    // Another activity is taking focus (this activity is about to be "paused").
}

@Override
protected void onStop() {
    super.onStop();
    // The activity is no longer visible (it is now "stopped")
}

@Override
protected void onDestroy() {
    super.onDestroy();
    // The activity is about to be destroyed.
}

3. Android Services: While our app doesn't currently use any services, a service could be added to play music in the background while the user interacts with the app.

4. Android Manifest File: The AndroidManifest.xml file for our app declares MainActivity as an activity.

<manifest xmlns:android="<http://schemas.android.com/apk/res/android>"
    package="com.example.myfirstapp" >

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme" >
        <activity android:name=".MainActivity" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

In this example, we have seen how the Android SDK, the activity lifecycle, and the Android Manifest file play crucial roles in app development. The concepts of services have also been touched upon, although they were not used in this simple app.