Android Development

In this lesson, you will learn how to set up the development environment uses to create applications in Android.

We'll cover the following

Android Studio IDE

Google provides great tooling to build Android applications, and the main one is the Android Studio IDE. It’s based on IntelliJ IDEA and provides tons of features, like:

With Android Studio, we can test applications either on an emulator or directly on the device.

Through this course, we will use Educative’s Android widget, which provides a pre-configured environment to build and launch Android applications in your browser so you don’t need to do any setup.

Here is Educative’s Android widget with a basic “Hello World” application. The actual code will be discussed in the coming lessons.

package com.educative.android.hello;

import android.app.Activity;
import android.os.Bundle;

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

However, if you want, you can install Android Studio, create the project, and copy the code provided in this course into your project.

Programming languages

There are 3 programming languages and 1 markup language that are used in Android development:

  • Java/Kotlin: source code
  • Groovy: build scripts
  • XML: layout structure and resources

Java is the official language for Android development, and it is supported by Android Studio. Java classes are compiled into a proprietary bytecode format and run on Android Runtime (ART) or Dalvik, a specialized virtual machine (VM) designed for Android.

Android supports all Java 7 language features and a subset of the Java 8 language features that vary by platform version.

Here is an example of an Android MainActivity.java file. We will discuss it in more detail in the following lessons:

public class MainActivity extends AppCompatActivity {



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);



        TextView mainTextView = findViewById(R.id.mainTextView);

        mainTextView.setText("Hello educative.io");

    }

}

Kotlin has been a second official language for Android Development since 2017. Kotlin is an Android-compatible language that is concise, expressive, and designed to be type and null-safe.

Through this course, we will use Kotlin, since it’s a more modern way to write Android applications.

Here is an example of an Android MainActivity.kt file so you can compare it to the MainActivity.java file example.

public class MainActivity : AppCompatActivity {



    override fun onCreate(savedInstanceState: Bundle) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)



        val mainTextView = findViewById<TextView>(R.id.mainTextView)

        mainTextView.text = "Hello educative.io"

    }

}

The Android build system is powered by Gradle. It is an open-source, build-automation system that builds upon the concepts of Apache Ant and Apache Maven and introduces a Groovy-based, domain-specific language (DSL).

Here is an example of a Gradle build file. We will discuss Gradle in more detail in the following lessons:

apply plugin: 'com.android.application'
android {
    defaultConfig {
        applicationId "com.travelblog"
        versionCode 1
        versionName "1.0"
    }
}
dependencies {
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'com.google.android.material:material:1.1.0-alpha10'
}

XML is heavily used in Android to declare a layout for the user interface, strings, dimensions, and some other resource files.

Here is an example of a layout that shows text in the middle of the screen. We will discuss it in more detail in the following lessons:

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout

        xmlns:android="http://schemas.android.com/apk/res/android"

        xmlns:app="http://schemas.android.com/apk/res-auto"

        android:layout_width="match_parent"

        android:layout_height="match_parent">



    <TextView

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="Hello World!"

            app:layout_constraintBottom_toBottomOf="parent"

            app:layout_constraintLeft_toLeftOf="parent"

            app:layout_constraintRight_toRightOf="parent"

            app:layout_constraintTop_toTopOf="parent" />



</androidx.constraintlayout.widget.ConstraintLayout>