Activity in android sdk

What Is the Android SDK and How to Start Using It

Android SDK is a software development kit developed by Google for the Android platform. The Android SDK allows you to create Android apps, and you don’t need to be an expert to use it. In this tutorial, I’ll explain what the Android SDK is and how to get started with it.

Android SDK comes bundled with Android Studio, Google’s official integrated development environment (IDE) for the Android operating system. You can learn about Android Studio and the Android App Development Kit in another of my articles.

In this post, we’ll look at:

• What is the Android SDK?
• How to install the Android SDK
• What is the Android SDK Manager?
• What are the components of the Android SDK?

What Is the Android SDK?

The Android SDK is a collection of software development tools and libraries required to develop Android applications. Every time Google releases a new version of Android or an update, a corresponding SDK is also released which developers must download and install. It is worth noting that you can also download and use the Android SDK independently of Android Studio, but typically you’ll be working through Android Studio for any Android development.

The Android SDK comprises all the tools necessary to code programs from scratch and even test them. These tools provide a smooth flow of the development process from developing and debugging, through to packaging.

The Android SDK is compatible with Windows, macOS, and Linux, so you can develop on any of those platforms.

How to Install the Android SDK

The Android SDK is optimized for Android Studio, and hence to effectively reap its benefits, you will need to install Android Studio. Having the Android SDK managed from within Android Studio is easier since support for languages like Java, Kotlin, and C++ is handled automatically. Not only that, but updates to the Android SDK are handled automatically by Android Studio.

To install the Android SDK from within Android Studio, first start Android Studio.

• From the Android Studio start page, select Configure > SDK Manager.

• If you already have Android Studio open, the SDK Manager icon is found on the top right corner, as shown below.

Install the required Android SDK platform packages and developer tools. A good start is to install:

• Android SDK Build-Tools
• Android Emulator
• Android SDK Platform-Tools
• Android SDK Tools
• Documentation for Android SDK

Click Apply, and Android Studio will install the selected tools and packages.

What Is the SDK Manager?

The Android SDK is composed of modular packages that you can download, install, and update separately using the Android SDK Manager. The SDK Manager helps to update new SDK releases and updates whenever a new Android platform is released. The SDK manager can be found in the top-right corner of the Android Studio screen, as shown below.

All that is required to follow the instructions provided, and the updates will be immediately downloaded to your environment.

What Are the Components of the Android SDK?

The Android SDK consists of an emulator, development tools, sample projects with source code, and the required libraries to build Android applications. Let’s look at the key components one by one.

Android SDK Tools

Android SDK Tools is a component of the Android SDK. It includes a complete set of development and debugging tools for Android, and is included with Android Studio. The SDK Tools also consist of testing tools and other utilities required to develop an app.

SDK Build Tools

Build tools are required for building components for building the actual binaries for your Android app. Always ensure your build tools component is up to date by downloading the latest version in the Android SDK Manager.

SDK Platform-Tools

Android Platform-Tools are used to support the features for the current Android platform and are necessary for Android app development. These tools interface with the Android platform on the device you use for testing. They include:

• Android Debug Bridge (adb): This is a handy command-line tool that lets you communicate with a device. The adb command allows you to perform device actions, such as installing and debugging apps. It also provides access to a Unix shell that you can use to run a variety of commands on a device.
• fastboot: This lets you flash a device with a new system image.
• systrace: This tool helps collect and inspect timing information across all processes running on your device at the system level. It’s crucial for debugging app performance.

SDK Platform-Tools are backward compatible, so you need only one version of the SDK Platform-Tools.

SDK Platform

For each version of Android, there’s one SDK Platform available. These are numbered according to the Android version (e.g. Android 7 Nougat) and an API version (e.g. API Level 24). Before you build an Android app, you must specify an SDK Platform as your build target. Newer SDK Platform versions have more features for developers, but older devices may not be compatible with the newer platform versions.

Google APIs

Google provides a number of exclusive Google APIs to make developing your app easier. They also offer a system image for the emulator so you can test your app using the Google APIs.

Android Emulator

The Android Emulator is a QEMU-based device-emulation tool that simulates Android devices on your computer, allowing developers to test applications on different devices and Android API levels, without needing to have physical devices for each. The emulator comes with configurations for various Android phones, tablets, Wear OS, and Android TV devices.

The Android emulator provides almost all of the capabilities of a real Android device. You can perform the following activities:

• simulate phone calls and text messages
• simulate different network speeds
• specify the location of the device
• simulate hardware sensors such as rotation
• access Google Play Store and much more

Often it is faster and easier to test your app with an emulator instead of using a physical device.

Conclusion

In this post, we looked at some of the basics of the Android SDK. The Android SDK is the only way to develop for Android devices. Fortunately, it contains extensive documentation, tutorials, samples, best practice guidance, and an array of tools for many different development tasks.

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Android Studio comes with some default templates to help start an app, but these are very basic and provide minimal, generic functionality.

CodeCanyon is an online marketplace that has hundreds of additional templates, which are way more feature-rich and domain-specific too. You can save days, even months, of effort by using one of them.

An Android app template is a great way to jump-start your app project or to learn some new skills by exploring the source code of a professionally made app.

Take a look at some of our roundups of the best Android app templates:

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Tutorial: Create your first Android application

In this tutorial, we will create a simple yet fully-functional Android application that counts how many times you tap a droid image. After that, we will run it on an Android virtual device.

This tutorial covers a simple scenario to help you get started with Android development in IntelliJ IDEA. For comprehensive how-to guides and reference documentation, visit the Android Studio user guide.

Create a new Android project

Create a project

Launch IntelliJ IDEA. On the Welcome screen, click New Project . If you already have a project open, from the main menu select File | New | Project .

In the New Project wizard, select Android on the left.

If you don’t have the Android SDK configured, IntelliJ IDEA will detect this and prompt you to download it:

Select the components you want to install. If you haven’t installed the Android SDK tools before, all the required components will be preselected.

Optionally, modify the location for the Android SDK, and click Next :

Review the installation settings and click Finish to start the download:

When all components have been downloaded and installed, click Finish :

Select Empty Activity as the project template:

On the last step, type HelloDroid as the project name and select Java as the language:

Configure project JDK

Now that we have created our first project, let’s make sure it uses the correct JDK.

From the main menu, choose File | Project Structure and go to Platform Settings | SDKs . Select the Android SDK and make sure that the correct Java version is selected in the Java SDK field.

We recommend that you use Java SE 11 or Java SE 8 for Android development in IntelliJ IDEA. If you don’t have the correct JDK installed, in the Project Structure dialog, click the Add New SDK button on the toolbar and select Download JDK :

In the Settings/Preferences dialog ( Ctrl+Alt+S ), go to Build, Execution, Deployment | Build Tools | Gradle and select the correct Java version (8.x or 11.x).

Explore the project structure

For Android projects, there’s a dedicated view in the IntelliJ IDEA Project tool window: click Project in the top-left corner and select Android .

This view doesn’t reflect the actual hierarchy of files on your disk — it is organized by modules and file types to ease navigation between source files of your project. Note that it hides project files and directories that you don’t commonly use (to see them, choose the Project view):

The app folder consists of the following subfolders:

manifests : contains the AndroidManifest.xml file, which holds general information about the application processed by the Android operating system. Among other things, it declares the package name that serves as a unique identifier for your application and the minimum version of the Android SDK required for the device where the application will run. It also declares the entry points of the application, along with permissions the application requires. For details, see App Manifest Overview.

java : contains the Java source code files grouped by packages, including JUnit tests.

res : contains all non-code resources, such as XML layout files, UI strings, images, and so on.

The Gradle Scripts folder contains all the project’s build-related configuration files.

Edit the UI layout

At this stage, the user interface of our sample HelloDroid application is based on a very simple layout defined in the activity_main.xml file located in the res/layout folder.

Let us modify the auto-generated user interface and see how the application layout is rendered without running it on any physical or virtual device.

Open the UI designer

In the Android project view, go to the app/res/layout and double-click the activity_main.xml file to open it. Note that since IntelliJ IDEA downloads the components required to render layout files, opening it may take a few seconds.

If the UI designer fails to open, and you get the Design editor is unavailable until after a successful project sync error, press Ctrl+Shift+A , search for the Sync Project with Gradle Files action, and wait for the sync to finish.

By default, IntelliJ IDEA provides a graphical view of the layout file, but you can also switch to the source code view, or view the text and the graphical representation side by side — use the icons in the top-right corner of the UI Designer pane:

This pane shows a rectangular canvas that is synchronized with the layout definition and with the Component Tree , so any changes to the canvas are reflected there accordingly.

Normally, layout files have a layout manager as their root element (for example, LinearLayout , FrameLayout , ConstraintLayout , and so on). In our example, the root element in activity_main.xml is ConstraintLayout that is responsible for positioning the elements of the application interface. For the purpose of this tutorial, we are not going to modify it, but you can learn more about designing interfaces from Build a Responsive UI with ConstraintLayout.

To eliminate distraction and only see how your layout is represented, click the Select Design Surface icon in the top-left corner and choose Design :

Now let’s delete the existing text element. To do this, right-click the text label and choose Delete from the context menu.

Now the UI layout looks like the following, and we are ready to start designing the layout of our application:

Add image to the UI layout

Now let’s add a droid image to our layout.

In the Android project view, expand the app/res folder and drag the image you want to use into the drawable folder. For this tutorial, we’ve downloaded a Hello Droid image from the Internet and saved it with the dimensions 50×50 px.

Return to the activity_main.xml file opened in the Designer pane, from the Palette choose the ImageView element, and drag it to the canvas to the position where you want the image to appear.

In the Pick a Resource dialog that opens, choose the resource file you’ve added and click OK :

Next, we need to modify the default id of the imageView element to be able to reference it later.

Select it in the Component Tree and in the Attributes pane on the right, enter the new identifier in the id field: droidImage . Press Enter ; in the dialog that opens, confirm that you want to update all references to the image element id:

Add text to the UI layout

Now let’s add some text to our layout.

In the Palette pane, pick the TextView element and drag it to the canvas below the image.

The widget displays some default text: TextView . To change it and link it to a string, we need to create a new text resource.

Select the textView element in the Component Tree on the left. In the Attributes pane on the right, click the Pick a Resource icon next to the text attribute:

In the dialog that opens, click the Add resource to the module icon in the top left corner and choose String Value .

In the New String Value dialog, enter the resource name ( welcome_text ) and the resource value ( Hello! I’m a droid. ):

Click OK to save the value and then click OK in the Pick a Resource dialog.

Now let’s modify the textView element id the same way we did with imageView .

Select textView in the Component Tree on the left, and in the Attributes pane set the id to a new value: clickCounter .

Add style to text

Now let’s add some style to the text to make it look more appealing.

Pad the text a bit: locate the padding attribute, and set all values to 10dp :

Change the font color: locate the textColor attribute, and click the Pick a Resource icon next to it.

In the dialog that opens, click the Add resource to the module icon in the top left corner and choose Color Value .

Enter the resource name ( text_color ) and the value ( #9C27B0 ):

Change the font size: locate the TextSize property and click the Pick a Resource icon next to it.

In the dialog that opens, click the Add resource to the module icon in the top left corner and choose Dimension Value .

Enter the resource name ( text_size ) and the value ( 24sp ):

As a result, your user interface now looks like the following:

To check what your application UI looks like in landscape orientation, click the Orientation for Preview icon on the Designer toolbar and choose Landscape :

To preview what your layout looks like on different devices, select another device from the device list:

Make the application interactive

Although our sample application is fully functional at this point, it does not support any form of interaction yet. Let’s modify it to support tap events.

In the Android project view, locate the MainActivity file under app\java\com.example.hellodroid and double-click to open it.

MainActivity is not a very meaningful class name, so let’s rename it.

Right-click this file in the Android project view and choose Refactor | Rename from the context menu or press Shift+F6 . In the dialog that opens, change the class name HelloDroidActivity and click Refactor :

All references to this class will be updated automatically, and your application’s source code will look as follows:

Replace the code in HelloDroid.java with the following:

Note that the identifiers we’ve used in the source code correspond to those we’ve set in our layout definition file, otherwise our code would not work.

Build and run the application

Now let’s build our application and run it on a virtual device.

Configure Android virtual device

First of all, to be able to run our application, we need to configure a virtual device.

In the main IntelliJ IDEA toolbar, click the devices list and choose AVD Manager :

On the first step of the wizard, click Create Virtual Device :

On the next step, we need to select the hardware that our virtual device will emulate.

Let’s select Phone on the left, and choose Pixel 2 as the target device:

Choose the system image you want to mimic on the virtual device, that is the OS version, the Android API level, the application binary interface (ABI), and the target SDK version:

Click the Download link next to the system image you want to mimic on the virtual device. For this tutorial, we’ve chosen to download the R system image.

In the License Agreement dialog that opens, read the license agreement and accept it, then click Next and wait for the download to finish. When the system image has been downloaded, select it and click Next in the System Image step of the wizard.

On the last step, you can modify your virtual device name and select the startup size and orientation of the screen. Choose the portrait layout and click Finish :

The newly configured device appears in the Android Virtual Device Manager .

Run the application

On the main IntelliJ IDEA toolbar, make sure the automatically created Run configuration and the virtual device we’ve just configured are selected and click :

The Android emulator will launch after the build has successfully finished, with our application started:

Click the droid image and see how the application processes the tap events, counts them and returns the corresponding message:

For information on how to run the app on a hardware device, refer to Android Studio: Run apps on a hardware device.

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