├── .github ├── ISSUE_TEMPLATE.md └── PULL_REQUEST_TEMPLATE.md ├── .gitignore ├── LICENSE.txt ├── Readme.md ├── app ├── .gitignore ├── build.gradle ├── proguard-rules.pro └── src │ ├── androidTest │ └── java │ │ └── github │ │ └── nisrulz │ │ └── sample │ │ └── learnkotlin │ │ └── ExampleInstrumentedTest.java │ ├── main │ ├── AndroidManifest.xml │ ├── java │ │ └── github │ │ │ └── nisrulz │ │ │ └── sample │ │ │ └── learnkotlin │ │ │ ├── MainActivity.kt │ │ │ ├── Operator.kt │ │ │ ├── User.kt │ │ │ └── UtilityClass.kt │ └── res │ │ ├── layout │ │ └── activity_main.xml │ │ ├── mipmap-hdpi │ │ └── ic_launcher.png │ │ ├── mipmap-mdpi │ │ └── ic_launcher.png │ │ ├── mipmap-xhdpi │ │ └── ic_launcher.png │ │ ├── mipmap-xxhdpi │ │ └── ic_launcher.png │ │ ├── mipmap-xxxhdpi │ │ └── ic_launcher.png │ │ ├── values-w820dp │ │ └── dimens.xml │ │ └── values │ │ ├── colors.xml │ │ ├── dimens.xml │ │ ├── strings.xml │ │ └── styles.xml │ └── test │ └── java │ └── github │ └── nisrulz │ └── sample │ └── learnkotlin │ └── ExampleUnitTest.java ├── build.gradle ├── gradle └── wrapper │ ├── gradle-wrapper.jar │ └── gradle-wrapper.properties ├── gradlew ├── gradlew.bat ├── img └── github_banner.png └── settings.gradle /.github/ISSUE_TEMPLATE.md: -------------------------------------------------------------------------------- 1 | 2 | 3 | **Do you want to request a *feature* or report a *bug*?** 4 | 5 | **What is the current behavior?** 6 | 7 | **If the current behavior is a bug, please provide the steps to reproduce.** 8 | 9 | 10 | 11 | **Any logs, error output, bugreport etc?** 12 | 13 | 14 | **What is the expected behavior?** 15 | 16 | **Any other comments?** 17 | 18 | 19 | **What versions of software are you using?** 20 | + **Device Information:** 21 | 22 | + **Android Version:** 23 | 24 | + **Configuration Information:** 25 | 26 | + **Misc:** 27 | 28 | -------------------------------------------------------------------------------- /.github/PULL_REQUEST_TEMPLATE.md: -------------------------------------------------------------------------------- 1 | 2 | 3 | **What does this implement/fix? Explain your changes** 4 | 5 | **Does this close any currently open issues?** 6 | 7 | **Any relevant logs, error output, bugreport etc?** 8 | 9 | 10 | **Any other comments?** 11 | 12 | + **Where has this been tested?** 13 | 14 | + **Device Information:** 15 | 16 | + **Android Version:** 17 | 18 | + **Target Platform:** 19 | 20 | + **SDK Version:** 21 | 22 | + **Configuration Information:** 23 | 24 | + **Misc:** 25 | 26 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # [Android] ======================== 2 | # Built application files 3 | *.apk 4 | *.ap_ 5 | 6 | # Files for the Dalvik VM 7 | *.dex 8 | 9 | # Java class files 10 | *.class 11 | 12 | # Generated files 13 | bin/ 14 | gen/ 15 | 16 | # Gradle files 17 | .gradle/ 18 | build/ 19 | /*/build/ 20 | .gradletasknamecache 21 | 22 | # Local configuration file (sdk path, etc) 23 | local.properties 24 | 25 | # Proguard folder generated by Eclipse 26 | proguard/ 27 | 28 | # Log Files 29 | *.log 30 | 31 | 32 | ## Directory-based project format: 33 | .idea/ 34 | 35 | ## File-based project format: 36 | *.ipr 37 | *.iws 38 | 39 | ## Plugin-specific files: 40 | 41 | # IntelliJ 42 | out/ 43 | 44 | # mpeltonen/sbt-idea plugin 45 | .idea_modules/ 46 | 47 | # JIRA plugin 48 | atlassian-ide-plugin.xml 49 | 50 | # Crashlytics plugin (for Android Studio and IntelliJ) 51 | com_crashlytics_export_strings.xml 52 | 53 | 54 | # [Maven] ======================== 55 | target/ 56 | pom.xml.tag 57 | pom.xml.releaseBackup 58 | pom.xml.versionsBackup 59 | pom.xml.next 60 | release.properties 61 | 62 | 63 | # [Gradle-Android] ======================== 64 | # Ignore Gradle GUI config 65 | gradle-app.setting 66 | 67 | # Properties 68 | gradle.properties 69 | 70 | # Mobile Tools for Java (J2ME) 71 | .mtj.tmp/ 72 | 73 | # Package Files # 74 | *.war 75 | *.ear 76 | 77 | # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml 78 | hs_err_pid* 79 | 80 | # Misc 81 | /.idea/workspace.xml 82 | /.idea/libraries 83 | .DS_Store 84 | /captures 85 | **/*.iml -------------------------------------------------------------------------------- /LICENSE.txt: -------------------------------------------------------------------------------- 1 | 2 | Apache License 3 | Version 2.0, January 2004 4 | http://www.apache.org/licenses/ 5 | 6 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 7 | 8 | 1. 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We also recommend that a 186 | file or class name and description of purpose be included on the 187 | same "printed page" as the copyright notice for easier 188 | identification within third-party archives. 189 | 190 | Copyright 2016 Nishant Srivastava 191 | 192 | Licensed under the Apache License, Version 2.0 (the "License"); 193 | you may not use this file except in compliance with the License. 194 | You may obtain a copy of the License at 195 | 196 | http://www.apache.org/licenses/LICENSE-2.0 197 | 198 | Unless required by applicable law or agreed to in writing, software 199 | distributed under the License is distributed on an "AS IS" BASIS, 200 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 201 | See the License for the specific language governing permissions and 202 | limitations under the License. 203 | -------------------------------------------------------------------------------- /Readme.md: -------------------------------------------------------------------------------- 1 | ![Image](https://github.com/nisrulz/LearnKotlin/blob/master/img/github_banner.png) 2 | 3 | ### Show some :heart: 4 | [![GitHub stars](https://img.shields.io/github/stars/nisrulz/LearnKotlin.svg?style=social&label=Star)](https://github.com/nisrulz/LearnKotlin) [![GitHub forks](https://img.shields.io/github/forks/nisrulz/LearnKotlin.svg?style=social&label=Fork)](https://github.com/nisrulz/LearnKotlin/fork) [![GitHub watchers](https://img.shields.io/github/watchers/nisrulz/LearnKotlin.svg?style=social&label=Watch)](https://github.com/nisrulz/LearnKotlin) [![GitHub followers](https://img.shields.io/github/followers/nisrulz.svg?style=social&label=Follow)](https://github.com/nisrulz/LearnKotlin) 5 | [![Twitter Follow](https://img.shields.io/twitter/follow/nisrulz.svg?style=social)](https://twitter.com/nisrulz) 6 | 7 | #### Tutorials 8 | 9 | + [Kotlin Cheatsheet](https://learnxinyminutes.com/docs/kotlin/) 10 | 11 | 12 | License 13 | ======= 14 | 15 | Copyright 2016 Nishant Srivastava 16 | 17 | Licensed under the Apache License, Version 2.0 (the "License"); 18 | you may not use this file except in compliance with the License. 19 | You may obtain a copy of the License at 20 | 21 | http://www.apache.org/licenses/LICENSE-2.0 22 | 23 | Unless required by applicable law or agreed to in writing, software 24 | distributed under the License is distributed on an "AS IS" BASIS, 25 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 26 | See the License for the specific language governing permissions and 27 | limitations under the License. 28 | -------------------------------------------------------------------------------- /app/.gitignore: -------------------------------------------------------------------------------- 1 | /build 2 | -------------------------------------------------------------------------------- /app/build.gradle: -------------------------------------------------------------------------------- 1 | apply plugin: 'com.android.application' 2 | apply plugin: 'kotlin-android' 3 | apply plugin: 'kotlin-android-extensions' 4 | 5 | android { 6 | compileSdkVersion 29 7 | 8 | defaultConfig { 9 | applicationId "github.nisrulz.sample.learnkotlin" 10 | minSdkVersion 14 11 | targetSdkVersion 29 12 | versionCode 1 13 | versionName "1.0" 14 | testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner" 15 | } 16 | buildTypes { 17 | release { 18 | minifyEnabled false 19 | proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' 20 | } 21 | } 22 | sourceSets { 23 | main.java.srcDirs += 'src/main/kotlin' 24 | } 25 | } 26 | 27 | dependencies { 28 | implementation fileTree(dir: 'libs', include: ['*.jar']) 29 | 30 | testImplementation 'junit:junit:4.12' 31 | androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0' 32 | 33 | implementation 'androidx.appcompat:appcompat:1.1.0' 34 | implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version" 35 | } 36 | -------------------------------------------------------------------------------- /app/proguard-rules.pro: -------------------------------------------------------------------------------- 1 | # Add project specific ProGuard rules here. 2 | # By default, the flags in this file are appended to flags specified 3 | # in /Users/nishant/android_sdk/tools/proguard/proguard-android.txt 4 | # You can edit the include path and order by changing the proguardFiles 5 | # directive in build.gradle. 6 | # 7 | # For more details, see 8 | # http://developer.android.com/guide/developing/tools/proguard.html 9 | 10 | # Add any project specific keep options here: 11 | 12 | # If your project uses WebView with JS, uncomment the following 13 | # and specify the fully qualified class name to the JavaScript interface 14 | # class: 15 | #-keepclassmembers class fqcn.of.javascript.interface.for.webview { 16 | # public *; 17 | #} 18 | -------------------------------------------------------------------------------- /app/src/androidTest/java/github/nisrulz/sample/learnkotlin/ExampleInstrumentedTest.java: -------------------------------------------------------------------------------- 1 | package github.nisrulz.sample.learnkotlin; 2 | 3 | import android.content.Context; 4 | import androidx.test.InstrumentationRegistry; 5 | import androidx.test.runner.AndroidJUnit4; 6 | 7 | import org.junit.Test; 8 | import org.junit.runner.RunWith; 9 | 10 | import static org.junit.Assert.*; 11 | 12 | /** 13 | * Instrumentation test, which will execute on an Android device. 14 | * 15 | * @see Testing documentation 16 | */ 17 | @RunWith(AndroidJUnit4.class) 18 | public class ExampleInstrumentedTest { 19 | @Test 20 | public void useAppContext() throws Exception { 21 | // Context of the app under test. 22 | Context appContext = InstrumentationRegistry.getTargetContext(); 23 | 24 | assertEquals("github.nisrulz.sample.learnkotlin", appContext.getPackageName()); 25 | } 26 | } 27 | -------------------------------------------------------------------------------- /app/src/main/AndroidManifest.xml: -------------------------------------------------------------------------------- 1 | 2 | 4 | 5 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | -------------------------------------------------------------------------------- /app/src/main/java/github/nisrulz/sample/learnkotlin/MainActivity.kt: -------------------------------------------------------------------------------- 1 | package github.nisrulz.sample.learnkotlin 2 | 3 | // Get the references for all the views in the layout with a defined ID, via below import. 4 | // This is IMPORTANT to get reference of all views under the exact layout 5 | import android.os.Bundle 6 | import androidx.appcompat.app.AppCompatActivity 7 | import android.widget.Toast 8 | import kotlinx.android.synthetic.main.activity_main.* 9 | 10 | 11 | class MainActivity : AppCompatActivity() { 12 | 13 | override fun onCreate(savedInstanceState: Bundle?) { 14 | super.onCreate(savedInstanceState) 15 | setContentView(R.layout.activity_main) 16 | 17 | var stringToDisplay = "Hello Kotlin World!" 18 | 19 | /* Raw string is delimited by using triple quote (""") 20 | * Raw strings can contain newlines and any other characters. 21 | */ 22 | var rawStringToDisplay = """ 23 | fun helloWorld(val name : String) { 24 | println("Hello, world!") 25 | } 26 | """ 27 | 28 | //The null check can be simplified using safe call operator (?.) 29 | val number: Int? = null 30 | // This will be executed only if the number is not null 31 | number?.toString() 32 | 33 | // Explicitly throw a NullPointerException 34 | // number!!.toString() 35 | 36 | 37 | // Casting in done by using an 'as' keyword, here also using the Safe” cast operator '?' which 38 | // returns the null value instead of throwing an exception 39 | val x: String? = number as? String 40 | 41 | /* Static Layout Import 42 | Kotlin allows you to import all references to views from the layout with one import. 43 | 44 | The TextView from layout is imported as a TextView instance with the name equal to the ID of the view, 45 | with the name equal to the id in camelCase. 46 | 47 | Note: 1. You don’t need to write semicolons at the end of the lines in Kotlin because they are optional. 48 | 2. When using fragments, make sure imported View references are used after the onCreateView() function call. 49 | Import the layout in onCreateView() function and use the View references to setup the UI in onViewCreated(). 50 | The references won’t be assigned before the onCreateView() method has finished. 51 | */ 52 | txt_helloworld.text = stringToDisplay 53 | 54 | 55 | // Using the kotlin pojo class 56 | // More info about properties at https://kotlinlang.org/docs/reference/properties.html 57 | 58 | // Initializing using the primary constructor 59 | val userName = User("Nishant", "Srivastava") 60 | 61 | // Using contructor to initialize the User object and get value using the custom getter 62 | stringToDisplay += "\n\nUsing primary constructor\n" + "Hello " + userName.fullName 63 | 64 | // Initialize using default setter 65 | userName.firstName = "Harsh" 66 | userName.lastName = "Singh" 67 | 68 | stringToDisplay += "\n\nUsing default setter\n" + "Hello " + userName.fullName 69 | 70 | // Create the operator class instance and display it in the activity 71 | var operator = Operator("John", "Doe") 72 | stringToDisplay += "\n\nUsing inheritance\n" + "Hello " + operator.fullName 73 | 74 | // Using member function 75 | stringToDisplay += "\n\nUsing member function of User object\n" + userName.sayHello("Nishant") 76 | 77 | stringToDisplay += "\n\nUsing local member function\n" + add(5, 10) 78 | 79 | // Using a defined kotlin extension 80 | stringToDisplay += "\n\nUsing kotlin extensions\n" + userName.getUserAge(22) 81 | 82 | stringToDisplay += "\n\nUsing raw string\n$rawStringToDisplay" 83 | 84 | 85 | // Set the value in textview 86 | txt_helloworld.text = stringToDisplay 87 | 88 | 89 | /* Using lambdas 90 | 1. if parameters aren’t used, we can leave them out 91 | 92 | btn_toast.setOnClickListener({ toast("Click") }) 93 | 94 | 2. if the function is the last parameter, it can be moved out of the parentheses 95 | 96 | btn_toast.setOnClickListener() { toast("Click") } 97 | 98 | 3. if the function has only one parameter that is a function, parentheses can be left out 99 | 100 | btn_toast.setOnClickListener { toast("Click") } 101 | 102 | More info : https://kotlinlang.org/docs/reference/lambdas.html 103 | */ 104 | btn_toast.setOnClickListener { view -> toast("Click") } 105 | 106 | } 107 | 108 | private fun toast(s: String) { 109 | Toast.makeText(this, s, Toast.LENGTH_SHORT).show() 110 | } 111 | 112 | // Defining a kotlin extension 113 | // Extension functions don’t modify the original extended class, but are a convenient way of writing utility methods. 114 | fun User.getUserAge(age: Int): String { 115 | return "Age : $age" 116 | } 117 | 118 | // Defining a function in kotlin 119 | fun add(x: Int, y: Int): Int { 120 | return x + y 121 | } 122 | } 123 | -------------------------------------------------------------------------------- /app/src/main/java/github/nisrulz/sample/learnkotlin/Operator.kt: -------------------------------------------------------------------------------- 1 | package github.nisrulz.sample.learnkotlin 2 | 3 | /* 4 | Note that you have to delegate to the default constructor of the extended class, which is similar to 5 | calling super() method in the constructor of a new class in Java. 6 | */ 7 | class Operator(name1: String, name2: String) : User(name1, name2) -------------------------------------------------------------------------------- /app/src/main/java/github/nisrulz/sample/learnkotlin/User.kt: -------------------------------------------------------------------------------- 1 | package github.nisrulz.sample.learnkotlin 2 | 3 | /* Converted the Java file to kotlin 4 | 5 | 1.Constructor in Kotlin is defined as: 6 | 7 | class User constructor(firstName: String) { 8 | .. 9 | } 10 | 11 | however if the primary constructor does not have any annotations or visibility modifiers, 12 | the constructor keyword can be omitted: 13 | 14 | class User (firstName: String) { 15 | .. 16 | } 17 | 18 | NOTE : The primary constructor cannot contain any code. Initialization code can be placed in initializer blocks, which are 19 | prefixed with the init keyword: 20 | 21 | class User(firstName: String) { 22 | init { 23 | logger.info("User initialized with value ${firstName}") 24 | } 25 | } 26 | 27 | 2. Inheritance 28 | In Kotlin, all classes extend from Any, which is similar to Object in Java. By default, classes are closed, 29 | like final classes in Java. So, in order to extend a class, it has to be declared as open or abstract 30 | */ 31 | open class User(fName: String, lName: String) { 32 | /* 33 | When defining variables in Kotlin, there are two options: 34 | 1. Mutable variables, defined by var keyword. 35 | 2. Immutable variables, defined by val keyword. 36 | 37 | Note : 1. By default, properties are non-null types, meaning that they can’t accept null value. 38 | 2. By default, everything is of public scope. You don’t have to write public keyword again. 39 | To define a variable to accept a null value, a question mark must be added after the type. 40 | 3. by default, all getter and setter are implicitly available you dont need to define unless you want a custom version for the same. 41 | */ 42 | 43 | // Initializing properties using constructor variables 44 | var firstName: String? = fName 45 | var lastName: String? = lName 46 | 47 | // Custom getter 48 | val fullName: String? get() = "$firstName $lastName" 49 | 50 | // Defining a member function in kotlin 51 | // More info at https://kotlinlang.org/docs/reference/functions.html 52 | fun sayHello(name: String): String { 53 | return "Hello $name" 54 | } 55 | } 56 | -------------------------------------------------------------------------------- /app/src/main/java/github/nisrulz/sample/learnkotlin/UtilityClass.kt: -------------------------------------------------------------------------------- 1 | package github.nisrulz.sample.learnkotlin 2 | 3 | /* 4 | If a non-abstract class does not declare any constructors (primary or secondary), it will have a 5 | generated primary constructor with no arguments. The visibility of the constructor will be public. 6 | If you do not want your class to have a public constructor, you need to declare an empty primary 7 | constructor with non-default visibility: 8 | */ 9 | class UtilityClass private constructor() { 10 | 11 | } -------------------------------------------------------------------------------- /app/src/main/res/layout/activity_main.xml: -------------------------------------------------------------------------------- 1 | 2 | 14 | 15 | 21 | 22 |