Kotlin
If you have a passion for programming, learning the Kotlin programming language can be an excellent start. This powerful language combines the power of object-oriented programming with the simplicity of Java. The following Kotlin tutorials will show you how to write Android applications using Kotlin.
Before you start, you must install Java Development Kit (JDK). Android Studio comes with a bundled version. However, you can install your own JDK to have more control over the version you’re using. If you don’t want to install a custom JDK, you can use Terminal to make these changes.
Resources class
In Android development, you should be familiar with the Resources class. This class stores additional files that your app may need. These resources may include layout definitions, user interface strings, or animation instructions. Using this class in your application is important because different Android devices may require different kinds of resources. For example, you may need different layout resources to take advantage of extra screen space, or string resources to translate user interface text. By using resources, you can customize your app’s behavior and support different device configurations.
The Resources class contains helper methods that extract resources from the resource table. These methods must look up the resource table in order to retrieve the resource. Unlike static objects, the helper methods should be dynamic. For example, the “getResources” method in the Resources class returns a Resource object that contains a resource id and a resource offset.
View View
The Android platform is a huge challenge and requires a lot of learning. Most developers are similar to each other and are creating similar-looking apps, using the same design principles. Getting a leg up on the competition will mean learning additional skills that will put you ahead of the rest, such as following Material Design Guidelines and using Custom Views. This series of tutorials will help you develop these skills.
The View class is the building block for any user interface in Android. It is responsible for occupying a rectangular area on the screen and handling user events.
OnClick (View view) method
OnClick (View view) is a callback method used to handle the events triggered by a user clicking or tapping an element within your app. The method takes one argument – a class object implementing the View.OnClickListener interface. You should call this method whenever your app needs to respond to a button click. It also handles releases and touches. Unlike other callbacks, it returns no value if it doesn’t handle the event.
In an Android application, almost every View will fire the onClick event whenever the user clicks or touches it. The view’s onClickListener class will listen for such events and assign an instance to it when the View is clicked. The class can be a subclass of View or an interface.
Activity
An activity is a type of app in Android. It can be created, executed, and stopped. The Android OS calls onStart() on an activity to start or restart it. The onStart() method also gets called when a user switches between two applications. For example, if a user switches from Application A to Application B, the latter will be paused and Application A will be restarted when the user clicks on the icon of Application A.
After starting your activity, you should implement an OnClickListener that will enable it to detect a button click. Then, in the onClick method of your first activity, you should call the finish() method to destroy the second activity. Once the second activity is destroyed, you can pass its data to the first activity with putExtra(…) method.
Activities in an Android app
Activities are the main component of your Android application. These objects are responsible for managing the lifecycle of your app. Each activity has a UI associated with it. It is set using the setContentView() function, which takes a View object as a parameter. This view contains the layout file for the activity.
The first step in creating an Android app is to create an Activity Object. An Activity Object is a window in which your app’s users can interact with your app. Activities are usually full-screen windows, but you can create smaller or larger ones as you need.
Setting up an Android development project
When you first begin to use Android, you may be tempted to jump right in and start writing code, but there are a few things you need to set up first. You will need a development environment, which is a combination of tools and setup, that will allow you to start working on your project. This environment is typically a computer.
Android Studio includes a wizard that will help you set up your project. It will let you select the type of project you wish to create and populate it with code and resources. It will guide you through the process of creating a new project, displaying a list of categories, tabs, and sample codes.