英文:
How to pass callback function from Java to Kotlin class
问题
以下是您要求的翻译内容：
我有一个 Kotlin 类，如下所示（这只是一个示例，为了方便起见，因此它并没有执行任何有用的操作）
class MyKotlinClass(private val handleSomeCallBack: (ByteArray) -> Unit) {
private val someBuffer = BytesBuilder()
fun myFunction(bytesList: List<Byte>) {
handleSomeCallBack(someBuffer.toArray())
}
}
我想从 Java 类中调用此代码，因此在那个类中，我声明了以下内容：
public MyJavaClass() {
messageParser = new MyKotlinClass(this::handleSomeCallback);
}
传递的回调方法是：
private void handleSomeCallback(byte[] dataBytes) {
}
（MyKotlinClass 在文件中被正确声明）
我遇到的问题是，我无法弄清楚如何将回调传递给 MyKotlinClass 的构造函数。
我尝试了各种方法，包括：
messageParser = new MyKotlinClass(handleSomeCallback(dataBytes));
messageParser = new MyKotlinClass(this::handleSomeCallback(dataBytes));
但无论我尝试什么，都会收到错误。
我认为答案与 lambda 表达式有关，但我无法完全理解从 Java 中调用这个的语法应该是什么。
英文:
I have a Kotlin class as follows (this is a sample for ease, hence it doesn't 'do' anything useful)
class MyKotlinClass (private val handleSomeCallBack: (ByteArray) -> Unit) {
private val someBuffer = BytesBuilder()
fun myFunction(bytesList: List<Byte>) {
handleSomeCallBack(someBuffer.toArray())
}
}
I want to call this code from a java class, hence, in that class I have the following declared:
public MyJavaClass() {
messageParser = new MyClass(handleSomeCallback);
}
The callback method being passed is:
private void handleSomeCallback(byte[] dataBytes) {
}
(MyClass is correctly declared within the file)
The issue I'm having is that I can't figure out how to pass the callback to the constructor of MyKotlinClass.
I have tried a variety of things including
messageParser = new MyClass(handleSomeCallback(byte[] dataBytes));
messageParser = new MyClass(this::handleSomeCallback(byte[] dataBytes));
But no matter what I try I receive an error.
I believe the answer is to do with lambdas but I can't quite see what the syntax should be for calling this from Java.
答案1
得分: 1
你可以选择类似这样的方式：
MyKotlinClass instance = new MyKotlinClass(byteArray -> {
// 你的代码
return Unit.INSTANCE;
});
或者像@ADM在这里建议的那样，将Unit用作你单独方法的返回类型：
只需在你的应用程序build.gradle文件的android块中添加以下内容：
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
英文:
You can go with something like this:
MyKotlinClass instance = new MyKotlinClass(byteArray -> {
// your code
return Unit.INSTANCE;
});
Or use Unit as return type of your separate method like suggested by @ADM here
You just need to add
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
to your android block in app build.gradle
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