{"id":5098,"date":"2023-01-18T13:01:09","date_gmt":"2023-01-18T03:01:09","guid":{"rendered":"https:\/\/learntodroid.com\/?p=5098"},"modified":"2023-01-18T13:01:15","modified_gmt":"2023-01-18T03:01:15","slug":"generating-random-numbers-in-kotlin-for-android","status":"publish","type":"post","link":"http:\/\/10.0.0.14:32769\/generating-random-numbers-in-kotlin-for-android\/","title":{"rendered":"Generating Random Numbers in Kotlin for Android"},"content":{"rendered":"\n<p>Randomness is required in a wide variety of different Android applications. For example, if you wanted your Android app to roll a die, flip a coin, or draw a card from a shuffled deck of cards, you will need some form of random number generation to achieve this.<\/p>\n\n\n\n<p><strong>Kotlin makes it really easy to generate random numbers to use in your Android app.<\/strong><\/p>\n\n\n\n<p><strong>To generate a random integer within a range of two numbers, you can define an <a rel=\"noreferrer noopener\" href=\"https:\/\/kotlinlang.org\/api\/latest\/jvm\/stdlib\/kotlin.ranges\/-int-range\/\" data-type=\"URL\" data-id=\"https:\/\/kotlinlang.org\/api\/latest\/jvm\/stdlib\/kotlin.ranges\/-int-range\/\" target=\"_blank\">IntRange<\/a> and then invoke the <a rel=\"noreferrer noopener\" href=\"https:\/\/kotlinlang.org\/api\/latest\/jvm\/stdlib\/kotlin.ranges\/random.html\" data-type=\"URL\" data-id=\"https:\/\/kotlinlang.org\/api\/latest\/jvm\/stdlib\/kotlin.ranges\/random.html\" target=\"_blank\">random()<\/a> function on the IntRange which will return a random integer that falls within the range.<\/strong><\/p>\n\n\n\n<p><strong>For example, if you wanted to generate a random integer between 1 and 10, you would use the following code.<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"><strong>var randomInteger = (1..10).random()<\/strong><\/pre>\n\n\n\n<p>In the blog post below I will take you through some other ways to generate randomness in your Android app using Kotlin.<\/p>\n\n\n\n<p>I will include code examples written in Kotlin that cover:<\/p>\n\n\n\n<ul>\n<li>How to generate a random integer (using a simulated dice roll as an example)<\/li>\n\n\n\n<li>How to generate a list of random integers (in just one line of code)<\/li>\n\n\n\n<li>How to generate a random double (in just one line of code)<\/li>\n\n\n\n<li>How to select a random item from a list (using a coin flip as an example) <\/li>\n\n\n\n<li>How to shuffle a list in random order (using a playing cards deck as an example)<\/li>\n<\/ul>\n\n\n\n<p>All of the code shared in this tutorial is available on GitHub in the link below.<\/p>\n\n\n\n<p><a rel=\"noreferrer noopener\" href=\"https:\/\/github.com\/learntodroid\/RandomNumbersKotlinAndroid\" target=\"_blank\">https:\/\/github.com\/learntodroid\/RandomNumbersKotlinAndroid<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">How to Generate a Random Integer in Kotlin<\/h2>\n\n\n\n<p>I will include some of the code shared in the introduction of this post for generating a random integer to use in an Android app that simulates rolling a 6-sided dice.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"356\" height=\"74\" src=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-1.png\" alt=\"\" class=\"wp-image-5129\" srcset=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-1.png 356w, http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-1-300x62.png 300w\" sizes=\"(max-width: 356px) 100vw, 356px\" \/><figcaption class=\"wp-element-caption\">Simple Dice Rolling Android App<\/figcaption><\/figure><\/div>\n\n\n<p>For the random number generation, I will create a Kotlin object called RandomSingleton that will be used as a singleton, meaning that only one instance of the object can be created and used throughout the app.<\/p>\n\n\n\n<p>RandomSingleton will include a function called randomInteger that has two Int params which are the from and to values to be used for the range of the random number.<\/p>\n\n\n\n<p>Then I will create an IntRange using those from and to numbers and call the random() function and return the random integer provided.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/4237da9a2270352fb66a8dfe4b8b2b56.js\"><\/script><\/p>\n\n\n<p>In the MainActivity, I will use a Jetpack Compose Composable function to display a Text element showing the rolled number and a Button to roll the dice<\/p>\n\n\n\n<p>When the Button is clicked it will use the randomInteger function on the RandomSingleton passing the from and to values as 1 and 6 respectively which will return the number of a random dice roll.<\/p>\n\n\n\n<p>The app will also display a Toast message with the random number after it has been rolled.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/46a473988c24f7c3c79b00aa351cc555.js\"><\/script><\/p>\n\n\n<h2 class=\"wp-block-heading\">How to Generate a List of Random Numbers in Kotlin<\/h2>\n\n\n\n<p>In Kotlin, you can generate a list of random numbers between two numbers by using the random() function on an IntRange along with the map function.<\/p>\n\n\n\n<p>See the code excerpt from the RandomSingleton object below containing the function listOfRandomNumbers which shows how to accomplish this in just one line of code.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/7d7bc607d4f898723802c80e541d05a5.js\"><\/script><\/p>\n\n\n<p>To make use of the listOfRandomNumbers function in your MainActivity, see the code sample below that contains a Composable function called RandomList that takes in the size of the list and minimum and maximum values for the random numbers.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/10c99dcfde193dbc633de70c905bdebb.js\"><\/script><\/p>\n\n\n<p>It displays the list of generated random numbers using the listOfRandomNumbers function from the RandomSingleton object inside a Text element with a Button displayed underneath. When the Button is clicked it will re-generate and show the random numbers.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"353\" height=\"72\" src=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-2.png\" alt=\"\" class=\"wp-image-5145\" srcset=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-2.png 353w, http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-2-300x61.png 300w\" sizes=\"(max-width: 353px) 100vw, 353px\" \/><\/figure><\/div>\n\n\n<h2 class=\"wp-block-heading\">How to Generate a Random Double in Kotlin<\/h2>\n\n\n\n<p>In Kotlin, you can use the nextDouble function on the <a rel=\"noreferrer noopener\" href=\"https:\/\/kotlinlang.org\/api\/latest\/jvm\/stdlib\/kotlin.random\/-random\/\" data-type=\"URL\" data-id=\"https:\/\/kotlinlang.org\/api\/latest\/jvm\/stdlib\/kotlin.random\/-random\/\" target=\"_blank\">Random class<\/a> to generate a random Double that falls within the range of two numbers.<\/p>\n\n\n\n<p>The nextDouble function takes two parameters both of the type Double.<\/p>\n\n\n\n<p>The random Double that is generated by the nextDouble function will be greater than or equal to the first parameter and will be less than the second parameter.<\/p>\n\n\n\n<p>I have updated the RandomSingleton object to include a function for generating a random Double called randomDouble.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/fbaa81f440ca717dfd2dde4e3d190074.js\"><\/script><\/p>\n\n\n<p>To use the randomDouble function in the RandomSingleton object in the Android app, see a code excerpt below from the MainActivity class.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/824d1ae96bdd83ee7ff32d1acd0ef414.js\"><\/script><\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"356\" height=\"73\" src=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-3.png\" alt=\"\" class=\"wp-image-5158\" srcset=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-3.png 356w, http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-3-300x62.png 300w\" sizes=\"(max-width: 356px) 100vw, 356px\" \/><\/figure><\/div>\n\n\n<h2 class=\"wp-block-heading\">How to Select a Random Item from a List in Kotlin<\/h2>\n\n\n\n<p>In Kotlin, to retrieve a random item from a List all you need to do is call the random() function on a list and it will return a random item.<\/p>\n\n\n\n<p>I have updated the RandomSingleton object to include a function called randomStringFromList that takes a List of Strings as a parameter and will return a random item from that list using the random() function.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/8f46c68594f55af49369360134611696.js\"><\/script><\/p>\n\n\n<p>This can be used in the MainActivity class with the following code excerpt.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/45e0975a8db2db1328b101e7dfb5c17d.js\"><\/script><\/p>\n\n\n<p>In the MainActivity we are using the randomStringFromList function on the RandomSingleton object by passing a List of the two faces of a coin (heads and tails) then retrieving the random result, simulating a random coin flip.<\/p>\n\n\n\n<p>The result of the coin flip is shown in a Text element and the user can flip the coin again by clicking the Button.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"357\" height=\"71\" src=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-4.png\" alt=\"\" class=\"wp-image-5164\" srcset=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-4.png 357w, http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-4-300x60.png 300w\" sizes=\"(max-width: 357px) 100vw, 357px\" \/><figcaption class=\"wp-element-caption\">Simple Coin Flipping Android App<\/figcaption><\/figure><\/div>\n\n\n<h2 class=\"wp-block-heading\">How to Shuffle a List in Random Order in Kotlin<\/h2>\n\n\n\n<p>In Kotlin, to randomize the order of a list, you can call the shuffle() function on a list.<\/p>\n\n\n\n<p>I have updated the RandomSingleton object to include a function called shuffleListOfStrings that takes a MutableList of Strings as a parameter and will return the MutableList of Strings in a random order once it has been shuffled using the shuffle() function.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/ed9f5977ff59c79762709c65a5f6e328.js\"><\/script><\/p>\n\n\n<p>This can be used in the MainActivity class with the following code excerpt.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/07548de3f95569418176ac4f0e22e4e9.js\"><\/script><\/p>\n\n\n<p>The code above uses the shuffleListOfStrings function on the RandomSingleton object to take in a MutableList of Strings which are made up of a list of playing cards that need to be shuffled.<\/p>\n\n\n\n<p>The implementation for the Deck class is also provided below.<\/p>\n\n\n<p><script src=\"https:\/\/gist.github.com\/learntodroid\/15c17f19dd9c0783993f2623e09590cb.js\"><\/script><\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"357\" height=\"118\" src=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-5.png\" alt=\"\" class=\"wp-image-5175\" srcset=\"http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-5.png 357w, http:\/\/10.0.0.14:32769\/wp-content\/uploads\/2023\/01\/image-5-300x99.png 300w\" sizes=\"(max-width: 357px) 100vw, 357px\" \/><figcaption class=\"wp-element-caption\">Simple Playing Cards Shuffling Android App<\/figcaption><\/figure><\/div>","protected":false},"excerpt":{"rendered":"<p>Randomness is required in a wide variety of different Android applications. For example, if you wanted your Android app to roll a die, flip a coin, or draw a card<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","footnotes":""},"categories":[12],"tags":[],"acf":[],"_links":{"self":[{"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/posts\/5098"}],"collection":[{"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/comments?post=5098"}],"version-history":[{"count":5,"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/posts\/5098\/revisions"}],"predecessor-version":[{"id":5179,"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/posts\/5098\/revisions\/5179"}],"wp:attachment":[{"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/media?parent=5098"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/categories?post=5098"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/10.0.0.14:32769\/wp-json\/wp\/v2\/tags?post=5098"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}