- \n
- Java is very error-prone where Kotlin is less. It even handles one of the biggest and most unexpected mistakes in the industry which is \u201cnullability\u201d. Kotlin uses basic structure to ensure null-safety which makes the language great.<\/span><\/li>\n
- We love to make clean and fewer codes. It\u2019s easy to read, to understand. And obviously, less code means fewer errors. With Java, we have to write lots of code in order to achieve any simple thing done where with Kotlin, even simple things can be done in fewer lines.<\/span><\/li>\n
- As Kotlin is an open-source language, it is growing its own community very fast. And we know well, a bigger community is very useful for the developers.<\/span><\/li>\n
- Kotlin is 100% interoperable with Java which is a blessing for developers who are used to work in Java. You can call Java code from Kotlin and vice-versa seamlessly. Both Kotlin and Java generate the same bytecode.<\/span><\/li>\n
- Kotlin handles Null Pointer Exception (NPE) very well. It guards your code with null checks everywhere which are a time consuming and boring task. By default, all variables are non-null. If a nullable variable is needed, it needs to be marked with a \u201c?\u201d.<\/span><\/li>\n
- One will get great IDE and tooling support for Kotlin. Nothing to worry about in with continuing support, because a well-established company backs it. JetBrains has created many amazing and widely used IDEs in the world. Even if anyone wants his Java file to be converted in Kotlin, they can use the \u201cConvert Java File to Kotlin\u201d option from the IDE.<\/span><\/li>\n<\/ul>\n
Steps to start developing Android applications using Kotlin?<\/b><\/h3>\n
We use Android studio IDE to develop an Android application. We will go through the steps to make a simple Android application using Kotlin in Android studio. For the steps, we can assume that you have the latest version of Android Studio and Java Virtual Machine (JVM) preinstalled on your computer.<\/p>\n
Step 1:<\/strong><\/h4>\n
Open your Android studio. At the time of writing, we are using version 3.4.2 of it. Next click on the Start a new Android Studio project.<\/p>\n
![\"Learn](\"https:\/\/toptechytips.com\/wp-content\/uploads\/2019\/07\/Learn-Android-Development-with-Kotlin-02.jpg\")
Learn Android Development with Kotlin<\/figcaption><\/figure>\n Step 2:<\/b><\/h4>\n
Here we can choose any kind of activity to start our project. For now, we will choose \u201cEmpty Activity\u201d as we don\u2019t need any pre-ready component in our page. Then we will click on \u201cNext\u201d.<\/p>\n
![\"\"](\"https:\/\/toptechytips.com\/wp-content\/uploads\/2019\/07\/Learn-Android-Development-with-Kotlin-05.jpg\")
<\/p>\nStep 3:<\/b><\/h4>\n
Now we will put our required information into the fields. Our application name will be \u201cFirst Kotlin App\u201d for now. We are keeping the package name as an example and choosing the Kotlin language as our application language. Later on, we will click on \u201cFinish\u201d.<\/p>\n
![\"Learn](\"https:\/\/toptechytips.com\/wp-content\/uploads\/2019\/07\/Learn-Android-Development-with-Kotlin-07.jpg\")
Learn Android Development with Kotlin\f<\/span><\/figcaption><\/figure>\n Step 4<\/b>:<\/span><\/h4>\n
Soon, the Gradle will start to synchronize the project materials.<\/p>\n
![\"\"](\"https:\/\/toptechytips.com\/wp-content\/uploads\/2019\/07\/Learn-Android-Development-with-Kotlin-01.jpg\")
Learn Android Development<\/figcaption><\/figure>\n Step 5:<\/b><\/h4>\n
Open the file named \u201cMainActivity\u201d. If we look closely, then it is visible to us the file is written in Kotlin language. Now, we are going to look over the application design. Therefore, we will open the file named \u201cactivity_main.xml\u201d. Let\u2019s see the codes of \u201cMainActivity\u201d before going there.<\/p>\n
package com.example.firstkotlinapp\r\nimport androidx.appcompat.app.AppCompatActivity\r\nimport android.os.Bundle\r\nclass MainActivity : AppCompatActivity() {\r\n override fun onCreate(savedInstanceState: Bundle?)\r\n super.onCreate(savedInstanceState)\r\n setContentView(R.layout.activity_main)\r\n }\r\n}<\/pre>\n![\"\"](\"https:\/\/toptechytips.com\/wp-content\/uploads\/2019\/07\/Learn-Android-Development-with-Kotlin-04.jpg\")
Learn Android Development with Kotlin<\/figcaption><\/figure>\n Step 6:<\/b><\/h4>\n
This is our design file. We can put our preferred design using XML here and then inflate it. For now, the \u201cHello World!\u201d is visible at the center of the page within a TextView. Let\u2019s have a look at codes,<\/p>\n
<?XML version=\"1.0\" encoding=\"utf-8\"?>\r\n<androidx.constraintlayout.widget.ConstraintLayout\r\n xmlns:android=\"http:\/\/schemas.android.com\/apk\/res\/android\"\r\n xmlns:tools=\"http:\/\/schemas.android.com\/tools\"\r\n xmlns:app=\"http:\/\/schemas.android.com\/apk\/res-auto\"\r\n android:layout_width=\"match_parent\"\r\n android:layout_height=\"match_parent\"\r\n tools:context=\".MainActivity\">\r\n<TextView\r\n android:layout_width=\"wrap_content\"\r\n android:layout_height=\"wrap_content\"\r\n android:text=\"Hello World!\"\r\n app:layout_constraintBottom_toBottomOf=\"parent\"\r\n app:layout_constraintLeft_toLeftOf=\"parent\"\r\n app:layout_constraintRight_toRightOf=\"parent\"\r\n app:layout_constraintTop_toTopOf=\"parent\"\/>\r\n<\/androidx.constraintlayout.widget.ConstraintLayout><\/pre>\n
![\"Learn](\"https:\/\/toptechytips.com\/wp-content\/uploads\/2019\/07\/Learn-Android-Development-with-Kotlin-08.jpg\")
Learn Android Development with Kotlin<\/figcaption><\/figure>\n Step 7:<\/b><\/h4>\n
Now we will run the application using our physical Android device, Xiaomi Redmi Note 7 Pro. Click on \u201cOK\u201d now.<\/p>\n
Learn Android Development with Kotlin<\/figcaption><\/figure>\n Step 8:<\/b><\/h4>\n
Now the application is in front of us now. This is our very first Android application written in Kotlin.<\/p>\n
![\"\"](\"https:\/\/toptechytips.com\/wp-content\/uploads\/2019\/07\/Learn-Android-Development-with-Kotlin-03-473x1024.jpg\")
Learn Android Development with Kotlin<\/figcaption><\/figure>\n Syntax Changes (Java to Kotlin)<\/b><\/h4>\n
It\u2019s time to go through some pieces of code. We will see some basic differences in coding syntax between Java and Kotlin.<\/p>\n
Terminator of Statement<\/b><\/h4>\n
In Java, we have \u2018;\u2019 as our terminator of a statement which means, we put it at the end of every statement to mark it as complete.<\/p>\n
\/\/Java\r\n Log.d(TAG, \u201cHello, I am a log\u201d);\r\n\/\/Kotlin\r\n Log.d(TAG, \u201cHello, I am a log\u201d)<\/pre>\n
Thus, we are using the same statement in respectively Java and Kotlin language above.<\/p>\n
Inheritance<\/b><\/h4>\n
We are used to with the \u201cextend\u201d keyword to inherit any class while writing its child class in Java. But in Kotlin, we don\u2019t need to use the keyword. Rather we will use the \u201c:\u201d character to indicate the inheritance. Let\u2019s see some codes,<\/p>\n
\/\/ Java way to inherit the AppCompatActivity using the extends keyword\r\n public class MainActivity extends AppCompatActivity {}\r\n\/\/ Kotlin way to inherit the AppCompatActivity using the : keyword\r\n class MainActivity : AppCompatActivity() {}<\/pre>\nNullable Variable<\/h4>\n
In Java, we don\u2019t have an option to handle nullability. It is like variables in Java can contain null in common. But in Kotlin, by default, not all the variables can contain null. To assign null to a variable, we need to make it nullable by adding \u2018?\u2019 to the type of it. Let\u2019s see some codes,<\/p>\n
\/\/Java way to access a UI button\r\n private Button mMyButton;\r\n mMyButton = (Button)findViewById(R.id.my_button);\r\n mMyButton.setText(\u201cMy Button\u201d);\r\n\/\/ Kotlin way to access a UI button\r\n private var mMyButton: Button? = null\r\n mMyButton = findViewById(R.id.my_button) as Button?\r\n mMyButton.text = \u201cMy Button\u201d<\/pre>\n
Overridden Methods<\/b><\/h4>\n
We usually see @override annotation over overridden methods in Java (which is optional). But in Kotlin, it has been set strictly to put override before function head to ensure the method is overridden and its readability. Let\u2019s see some codes,<\/p>\n
\/\/Java way to write an overridden method\r\n @Override\r\n protected void onCreate(Bundle savedInstanceState) {\r\n }\r\n\/\/Kotlin way to write an overridden method\r\n override fun onCreate(savedInstanceState: Bundle?) {\r\n }<\/pre>\nType Casting<\/b><\/h4>\n
We sometimes want to convert our object of a type to another type which is called typecasting. In Java, we generally use \u201c(Casting Type)\u201d before the object to make the typecasting. But in Kotlin, there are some changes. Kotlin has introduced a new keyword named \u201cas\u201d to typecast the objects. Let\u2019s see some codes,<\/p>\n
\/\/Java way to typecast an object\r\n mMyButton = (Button)findViewById(R.id.my_button);\r\n\/\/Kotlin way to typecast an object\r\n mMyButton = findViewById(R.id.my_button) as Button?<\/pre>\n
Setting Properties to an Object<\/b><\/h4>\n
In Java, we use setter methods to set the property to objects. It is a traditional way of setting values, whereas, In Kotlin, object property can be assigned just like a variable assignment. Let\u2019s see some codes,<\/p>\n
\/\/Java way to set text at a UI button\r\n private Button mMyButton;\r\n mMyButton = (Button)findViewById(R.id.my_button);\r\n mMyButton.setText(\u201cMy Button\u201d);\r\n\/\/Kotlin way to set text at a UI button\r\n private var mMyButton: Button? = null\r\n mMyButton = findViewById(R.id.my_button) as Button?\r\n mMyButton.text = \u201cMy Button\u201d\r\n<\/pre>\n
Model\/Data Class<\/b><\/h4>\n
\u00a0We need to use different constructors and lots of setter-getter methods in order to achieve the proper model class in Java whereas, it can be easily achieved with fewer codes using Data class in Kotlin. Let\u2019s see some codes,<\/p>\n
\/\/Java way to make a model class\r\n public class Student {\r\n private String mName, mClassName, mDepartment;\r\n private int mID;\r\n public Student(String mName, String mClassName, String mDepartment, int mID) {\r\n this.mName = mName;\r\n this.mClassName = mClassName;\r\n this.mDepartment = mDepartment;\r\n this.mID = mID;\r\n}\r\npublic Student(String mName, String mClassName, int mID) {\r\n this.mName = mName;\r\n this.mClassName = mClassName;\r\n this.mDepartment = \"DEFAULT\";\r\n this.mID = mID;\r\n }\r\npublic String getName() {\r\n return mName;\r\n }\r\npublic void setName(String name) {\r\n mName = name;\r\n }\r\npublic String getClassName() {\r\n return mClassName;\r\n }\r\npublic void setClassName(String className) {\r\n mClassName = className;\r\n }\r\npublic String getDepartment() {\r\n return mDepartment;\r\n }\r\npublic void setDepartment(String department) {\r\n mDepartment = department;\r\n }\r\npublic int getID() {\r\n return mID;\r\n }\r\npublic void setID(int ID) {\r\n mID = ID;\r\n }\r\n}\r\n\/\/Kotlin way to make a model class\r\n data class Student (\r\n var name: String,\r\n var className: String,\r\n var department: String = \"DEFAULT\",\r\n var id: Int\r\n )\r\n<\/pre>\n - We love to make clean and fewer codes. It\u2019s easy to read, to understand. And obviously, less code means fewer errors. With Java, we have to write lots of code in order to achieve any simple thing done where with Kotlin, even simple things can be done in fewer lines.<\/span><\/li>\n