You can delete all these: One approach that you can take is instead of trying to customize the Dialog by using setContentView, you can extend DialogFragment with a new Custom Dialog Fragment. You may have noticed that some of the code you’ve replaced uses !!. Kotlin compiler by default doesn’t allow any types to have a value of null at compile-time. function, otherwise (i.e. !なんてやっちゃったら、場合によっては落ちます。 ただKotlinにはJavaにはないスコープ関数や拡張関数、エルビス演算子などがあります。 As @Declan Nnadozie already mentioned: btnYES = findViewById(R.id.btnYES) returns null because btnYES is not a view inside the contentView inflated to PageTwoActivity. For example, a normal property can’t hold a null value and will show a compile error. Optional usage requires creating a new object for the wrapper every time some value is wrapped or transformed to another type — with the exclusion of when the Optional is empty (singleton empty Optional is used). So, in Kotlin, a normal property can’t hold a null value. So here's the solution. So String? java.lang.IllegalStateException: findViewById(R.id.btnYES) must not be null, The error source is eluding us ! In this article, we’ll be looking at the null safety features built into the Kotlin language. 2. bottomnav FindViewById get null (kotlin) 158. In Kotlin, null can form special union types with any other type, making them “nullable” and denoting them with the question mark. To get started, you’ll need to add the kotlin … Tries to assign a nullable view to a lateinit non-nullable view. As we have a list of objects, we will compare the object properties in the predicate. change this btnYES = findViewById(R.id.btnYES) to this btnYES = findViewById(R.id.btnYES)!! It force-casts a nullable variable to a non-null … using find () : find () takes one predicate that returns one boolean. You may have noticed that some of the code you’ve replaced uses !!. april is the Month object with name April and days 30. Maven Dependency. !.findViewById(R.id.btnYES) to handle null references. 2. LINK. The Activity structure is as follows PageTwoActivity has its own XML file with two buttons attached. So next time you declare a variable in your code, don’t rush to add that little question mark and ask yourself the important questions. – still_dreaming_1 Jan 31 at 14:29 python - Is there a way to disable saving to checkpoints for Jupyter Notebooks? Once you’ve spent time hardening your code as just discussed, there will be times you know for sure you’ve instantiated a value. Returns a list containing all elements that are not null. The buttons btnYES and btnNO and the EditText etStudentName can be found in the content that is inflated in the dialog: Here is the PageTwoActivity code. The takeaway here is that null is not necessarily your only choice as a default value, ... Kotlin is but a tool, and a powerful one that is, but how you use that tool can make a world of difference. To do this, we just assign null to lastName. The custom dialog has its own xml file Let’s start with the representation. We have looked at a number of posts and tried a few with no results. At a higher level, a Kotlin type fits in either of the two. anyMatch() method takes a predicate, an expression or a function which returns a boolean value. In Kotlin, there is no additional overhead. January 31, 2020, at 02:40 AM. But the syntax could be reduced and is given below. In Android Studio 4.1+, when you create a new Kotlin project and try to connect an XML layout file with your .kt file using Kotlinx synthetic, you’ll see you can’t do it anymore. import kotlin.test. This might sound same as explicitly checking for a null value. kotlin.internal.InlineOnly public inline fun CharSequence?.isNotEmpty(): Boolean = this != null && length > 0 This would be more comprehensive, so … * fun main(args: Array) { //sampleStart val … Once you’ve spent time hardening your code as just discussed, there will be times you know for sure you’ve instantiated a value. var variable : CustomClass = CustomClass () variable = null //compilation error Then you can approach it similar to how you would a fragment; You inflate a view in onCreateDialog, this is an approach I found in a similar question: Licensed under cc by-sa 3.0 with attribution required. change this internal lateinit var btnYES: Button to this internal lateinit var btnYES: Button? Should we be inflating the custom dialog xml? Note, how we have used the Kotlin keyword when which is a Java analog of the switch-case statement but much more powerful and flexible. We have created a custom alert dialog that was used in a Java project by converting it to Kotlin The error posted below if… Kotlin Program – example.kt If you are familiar with Java, then must have encountered with NullPointerException and to remove this or in other words, we can say that to safely deal with this NullPointerException, the developers of Kotlin introduced Null safety. It also returns from the current function if x is null, so it does more than just only assigning x to y if x is not not null. Kotlin provides comprehensive, native handling of nullable fields – no additional libraries are needed. * fun main(args: Array) { //sampleStart val numbers: List = listOf(1, 2, null, 4) val nonNullNumbers = numbers.filterNotNull() println(nonNullNumbers) // [1, 2, 4] //sampleEnd } Returns a list containing only the non-null results of applying the given transform function to each element in the original array. Then you can approach it similar to how you would a fragment; You inflate a view in onCreateDialog, this is an approach I found in a similar question: https://androidpedia.net/en/knowledge-base/51851505/android-kotlin-findviewbyid-must-not-be-null#answer-0. In Kotlin, we can assign default values to arguments in function calls. In the above code, there will not be any problem on line 3 because fullName variable is not null. So next time you declare a variable in your code, don’t rush to add that little question mark and ask yourself the important questions. Also in Kotlin you do not need findViewById to access the activity's views. The Activity structure is as follows PageTwoActivity has its own XML file with two buttons attached. Based on this predicate, it will return the first element found or null if no element is found. https://typealias.com/guides/java-optionals-and-kotlin-nulls this link offers advice but we have no idea where to start Kotlin's type system is aimed at eliminating the danger of null references from code, also known as the The Billion Dollar Mistake.One of the most common pitfalls in many programming languages, including Java, is that accessing a member of a null reference will result in a null reference exception. Also in Kotlin you do not need findViewById to access the activity's views. In Kotlin, filtering conditions are defined by predicates – lambda functions that take a collection element and return a boolean value: true means that the given element matches the predicate, false means the opposite.. javascript - Ionic 3: Getting value from PlayStore link, sql server - SQL list account managers with predecessor. It checks it using a null check using != null and isEmpty() method of string. In this way, Kotlin with the help of smart casts and special operators make easy to handle null safely. Asserting Not-Null. The default value is used when the argument is omitted. NO name conflicts, So the question is how do we FIX the error? The code below shows both approaches: To get started, you’ll need to add the kotlin … If you checked your local variable and it’s not null, nothing in the world could make it null, so Kotlin compiler allows to treat is as a non-null value. That’s Kotlin’s non-null assertion operator. Hence let is inevitably being understood that it is the replacement of null check e.g. The Elvis operator will evaluate the left expression and will return it if it’s not null else will evaluate the right side expression. Edit Page Filtering. So I search in youtube and I seen a lot of content which uses Fragment for bottom navigation T_T. r - What does a tilde (~) in front of a single variable mean (facet_wrap)? Kotlin Null Safety. KotlinはNull安全なプログラム言語だといいますが、当然ながらNullを取りうる変数objに対して、obj! Null safety is one of the best features of Kotlin. The buttons btnYES and btnNO and the EditText etStudentName can be found in the content that is inflated in the dialog: python - Most elegant way to assign multiple variables to the same value. So, in Kotlin, a normal property can’t hold a null value. Null safety is one of the best features of Kotlin. Filtering is one of the most popular tasks in the collection processing. Nullability and Nullable Types in Kotlin. The buttons btnYES and btnNO and the EditText etStudentName can be found in the content that is inflated in the dialog: Also in Kotlin you do not need findViewById to access the activity's views. if a is not null, it calls the equals(Any?) 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