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Why Android Development?

Android Hardware

Hardware is the physical “hard” components of the phone, like the screen, battery, processor and motherboard, or even more obscure hardware devices like accelerometers, gyroscopes, proximity sensors, etc. The software is the intelligence that makes the phone run, manages all of the input/output, and runs the apps (in this case Android).

A simplified illustration of the hardware in a mobile phone. In the center of the illustration there is a mobile device with a blank screen. Extending out to the right from the center right edge of the device there is a line connected to an illustration of a battery in the top right corner of the illustration, and another line connected to an illustrated processor in the bottom right corner. From the center bottom edge of the device there is a line connected to an illustrated accelerometer. There is another line extending to the left from the top left corner of the device that is connected to an illustration of a proximity sensor. There is another line extending to the left from the left center edge of the device that is connected to an illustrated motherboard. Finally there is another line extending from the bottom left edge of the device connected to an illustration of a gyroscope.

Android Software

Software is the intelligence that operates the hardware, manages all of the input/output, and runs the apps. It’s the brain of the device.

A collection of various software application icons on a mobile device screen with a pink brain at the top of the illustration above the device. Layered on top of the brain in the center there is the green Android alien icon. There is a right pointing curved arrow pointing to the bottom left side of the brain, and another right pointing curved arrow on the other side of the brain pointing up and to the right. Under the brain there are short straight lines connected to the top edge of the device. The software applications on the device screen are organized into three rows of three application icons. The top row has the Spotify logo, the Youtube logo, and the Angry Birds game logo. The middle row contains the SoundCloud icon, the Vimeo icon, and a chess application icon. The bottom row contains the Google Play Music icon, the Microsoft Word icon, and a sudoku game icon. Each of these logos and icons are in the shape of a circle

Android Source Code Modification

Because the Android source code is modifiable by companies selling the phones, the actual user interface from device to device will vary as well. Depending on the brand of phone and when it was purchased the default UI may differ.

An illustration of many Android devices in a basket. At the top of the illustration there is a pink brain. Layered on top of the brain in the center there is the green Android alien icon. Extending from the brain are lines that have yellow and blue circles at the end and look like circuitry. Under the brain with the Android icon and circuitry there is a red shopping basket with four different Android devices.

Android Software Development Kit

The Android Software Development Kit contains the libraries and tools you need to develop Android Apps.

An illustration of the Android Software Development Kit. On the left side of the illustration there is a shelf of colorful books. In the center of the book shelf illustration there is a large white right angle bracket followed by a white underscore . To the right of the bookshelf there is the green Android alien icon that has a toolbelt on and has its right arm pointing up. The final illustration is to the right of the alien icon and is the mathematical symbol for a function (which looks like a lowercase letter 'f' followed by a lowercase letter 'x'). Under the Android alien icon there is the text 'SDK' to label the entire illustration.

Android Studio

Android Studio is an Integrated Development Environment (IDE) created by Google which is used to develop Android apps. Android Studio is a program specifically designed to make developing Android Apps easier, it helps to streamline development, and contains useful tools like a visual layout editor, a debugging suite, and a collection of device emulators to test your apps on. It also has the ability to load your app up on a real android device, and package your app for deployment to the Google Play Store.

Android Studio logo. The Android Studio logo is a compass used to draw circles. There is a hinge adjusted so the two legs form a sixty degree angle. The left most arm is pointing toward the bottom left corner (of the container it's in). The right most arm is pointing to the bottom right corner. The handle of the compass is pointing up. The compass legs and hinge are white, while the handle is dark gray. Behind the compass there is a circle where the top half of the circle is a darker green than the bottom half. The compass has shadows as if a light source is coming from the upper left area (of the container the logo is in).

How to Write Android Apps

Android apps are developed in one of two programming languages, either Java or Kotlin. Apps also utilize Extensible Markup Language (XML) which is used to describe data resources, build configuration files, and describe the UI of apps.

The logos for the Java and Kotlin programming languages. The Java logo is on the left, the Kotlin logo is on the right, and in the center there is an illustrated robot character. The Java logo is a line drawing of a steaming cup of coffee, with little detail. The cup and saucer is blue and the steam lines are red. The word 'Java' is in white below the coffee cup and saucer. The Kotlin logo is two triangles and a trapezoid that form a blocky letter 'K'. The triangles are a blue to purple gradient, while the trapezoid is a pink to orange gradient. The word 'Kotlin' is in white, below the blocky letter 'K'. The illustrated robot between the Java and Kotlin logos has a geometric body. The "head" is the shape of a half square with very rounded corners. Connected to the "head", with a centered vertical line as the "neck", is the "torso" which is a square. The upper "arms" are short, horizontal lines coming out from the body. There is a perpendicular line attached to each outer edge of the "upper" arms that starts above where the horizontal line attaches to the "torso" . These vertical lines are meant to be the "forearms", and the forearms are pointing down. The hands are horseshoe shaped with the opening of the horseshoe shape pointing down. The "legs" are connected to the "torso" via a centered vertical line. Connected to this vertical line is a horizontal line that is meant to be the upper "legs". There are two vertical lines (meant to be the lower "legs") on the very left and very right sides of the upper "legs" line. The lower "legs" are connected to the "feet". The "feet" are a capsule shape meant to look like the wheels of a track vehicle that has three wheels. The left and right half of the robot are mirrors of each other. The robot is various shades of blue. The right half of the robot has deeper tones of each shade of blue mirrored from the left side.

Android Virtual Devices

The Android emulator allows you to run your app on an Android Virtual Device (AVD), which behaves just like a physical Android device. You can set up numerous AVDs, each emulating a different type of device.

The Android emulator with an example of an Android Virtual Device (AVD) instance. The Android emulator has an AVD smartphone and a bar of device controls displayed. The AVD is displaying a live preview of a view that contains a status bar, a heading, text, and a button. The status bar is at the very top of the device screen. It takes up the full width of the device screen and about 2% of the device screen height. It shows the time, a settings (cog) icon, a security (shield) icon, and a file icon in the upper left corner of the bar. On the right side of the status bar there is a wifi icon, a cellular service (bars) icon, and a battery icon. The background is dark blue-green, with white font/icon color. Under the status bar there is a heading. The heading is a medium blue-green rectangle with text. The rectangle is the width of the device screen, and about 10% of the device screen height. There is the text, 'Hello World', on the left side of this rectangle in white font, with padding on the left of the word 'Hello'. The text is centered vertically in the rectangle. Under the heading there is the text 'Hello World!' The text is centered vertically and horizontally (in the remaining space of the device screen). The background color of the text is yellow while the text is dark gray. The text also takes up about 10% of the device screen's height. Under the 'Hello World!' text there is a button. The button is centered horizontally and vertically between the 'Hello World!' text and the bottom of the view. The button has the text 'Button' in all capital letters. The button text has padding on each side of the text and has a gray background and dark-gray text color. The button width is about 20% of the device screen width, and about 5% of the device screen height. At the bottom of the device under the view, there are device navigation controls. From left to right, the controls are: a back button (triangle), a home button (a circle), and a recently used apps button (square). These device navigation controls are light gray shapes that contrast with the black background of the device. To the right of the AVD there is a bar of device controls. The bar is a long vertical rectangle. At the top left of the bar there is a close (X) icon, and at the top right there is a minimize (minus) icon. Under the close and minimize icons there are the following controls: power button, volume up, volume down, rotate device left, rotate device right, camera, zoom-in, back button (triangle), home button (circle), and a recently used apps button (square). At the bottom of the controls bar, there is a more icon (three dots).

Integrated Development Environment

Android Studio is the official integrated development environment for Google’s Android operating system, built on JetBrains IntelliJ IDEA software and designed specifically for Android development. It is available for download on Windows, macOS and Linux based operating systems. It is a replacement for the Eclipse Android Development Tools as the primary IDE for native Android application development.

Android Studio logo. The Android Studio logo is a compass used to draw circles. There is a hinge adjusted so the two legs form a sixty degree angle. The left-most arm is pointing toward the bottom left corner (of the container it's in). The right-most arm is pointing to the bottom right corner. The handle of the compass is pointing up. The compass legs and hinge are white, while the handle is dark gray. Behind the compass there is a circle where the top half of the circle is a darker green than the bottom half. The compass has shadows as if a light source is coming from the upper left area (of the container the logo is in).
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Build Basic Android Apps with Java

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