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This article mainly explains "how to achieve Java and Kotlin Intermodulation". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to achieve Java and Kotlin Intermodulation".

1. Kt call-Java parameter non-null handling @ NotNullclass TestJava {public void toNotNull (@ NotNull String title) {} public void toNull (String title) {}} Kotlin call

II. Kt calls-variables and methods declared using the kt keyword in Java

The java method is called in kotlin. If the keyword Kotlin is included in the parameter, the backquotation mark ``must be added.

Public Object object;// uses the keyword named method public void is () {} Kotlin in kotlin to call testJava.`is` () testJava.`object`. Third, Kt invokes Java-SAM transformation

When calling a method with interface parameters in Kotlin, if there is only one method for this interface, then the SAM transformation can be implemented through lambda expressions, thus simplifying our code.

Examples are as follows:

Public class TestJavaSam {void singleFun (@ NotNull IListener iListener) {} void noParameter (@ NotNull IListener iListener,int sum) {} void noParameterClean (int sum,@NotNull IListener iListener) {}} interface IListener {void onClick () } call fun main () {val sam = TestJavaSam () sam.singleFun {} sam.noParameter in Kotlin ({/ / if you change the order of java method parameters, it will be more concise, as follows}, 123) sam.noParameterClean (123) {}} IV. Java is prohibited from calling a method @ JvmSynthetic in Kt.

In Kotlin, some methods do not want to be exposed to Java calls, so you can add this annotation to the method.

@ JvmSyntheticfun toMain () {}

ToMain () will not be called in Java at this time.

5. Java calls the Kt- extension function @ file:JvmName ("xx")

When we use the extension function of Kotlin in java, we all use the corresponding class name + Kt to call the relevant method. Sometimes we want to customize the corresponding tool class, which is a bit troublesome, as follows:

For example, we have a top-level extension function in UiExpand.kt:

Fun Int.px () {} * * Java calls * * / / Java calls the kotlin class-(UiExpand)-Int.px () extension method UiExpandKt.px (20)

As shown above, when called in Java, we must have the file name + kt suffix before we can call it.

By adding @ file:JvmName ("Ui") to the UiExpand.kt package name, we can implement the custom generated class name to call the

As follows:

Ui.px () VI. Java calls kt- member variable @ JvmField

In Java, when we call the member variables of Kotlin, the compiler will automatically generate the corresponding get,set methods for us, which is very consistent with the way Java Bean is written, but there are some that we just want to call directly, so we can do so at this time.

Kotlindata class TestKotlinBean (@ JvmField val message: String, @ JvmField val title: String) * * Java calls * * TestKotlinBean testKotlinBean = new TestKotlinBean ("", "); String message = testKotlinBean.message; String title = testKotlinBean.title

Of course, for the following example, even if you don't need to add the above comments, you can call it directly in java, eliminating get,set.

Lateinit var sum: Stringobject UserPicCache {const val KEY_CACHE = "CACHE"} @ get:JvmName,@set:JvmName

Sometimes we just want it to generate one of the set or get methods, and we can use the above annotation.

Kotlindata class TestKotlinBean (@ set:JvmName ("setMessage") var message: String, @ get:JvmName ("getTitle") val title: String)

Call in Java:

TestKotlinBean testKotlinBean = new TestKotlinBean ("", "); testKotlinBean.setMessage (" message "); testKotlinBean.getTitle (); VII. Java calls Kt- companion object @ JvmStatic

When we call a method or variable of a Kotlin companion object in Java, it must be called through the class name .Companion. Xx. At this point, we can increase

@ JvmStatic to call directly.

Kotlinclass Log {companion object {var time: String = "" fun toLog () {}

Call in Java:

ToLog.toLog (); ToLog.getTime ()

It is important to note, however, that @ JvmStatic does not improve performance because the compiler generates a static method accordingly, and two static methods set,get for variable variables.

8. Java calls the Kt- method default parameter value @ JvmOverloads

In Kotlin, we may add some default values for method parameters to facilitate better use, but in Java, if the corresponding method parameters are not passed during the call, an error will be prompted, which can be modified with the @ JvmOverloads method.

Kotlinobject DialogUtils {@ JvmStatic @ JvmOverloads fun showPromptDialog (title: String = "hint") {} calls DialogUtils.showPromptDialog (); DialogUtils.showPromptDialog ("title") in java; Thank you for reading, the above is the content of "how to achieve Java and Kotlin Intermodulation". After the study of this article, I believe you have a deeper understanding of how to achieve Java and Kotlin Intermodulation, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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