Is there a way to use Java 8 functional interfaces on Android API below 24?

Question

I can use retrolambda to enable lambdas with Android API level <24. So this works

myButton.setOnClickListener(view -> Timber.d(\"Lambdas work!\"));
         


        

Answer 1

Android support library(AndroidX) now has Consumer and Supplier:

• androidx.core.util.Consumer (appears in androidx.appcompat:appcompat:1.0.2)
• androidx.core.util.Supplier (appears in androidx.appcompat:appcompat:1.1.0-alpha01)

sadly only these two interfaces gets added as of writing.

Now we have Kotlin, it doesn't require you to specify the functional interface explicitly:

    fun test() {
        val text = withPrintStream {
            it.println("Header bla bla ")
            it.printf("%s, %s, %s,", "a", "b", "c").println()
        }
    }

    // Equivalent to the following code in Java:
    //     Consumer action;
    //     action.accept(ps);
    fun withPrintStream(action: (PrintStream) -> Unit): String {
        val byteArrayOutputStream = ByteArrayOutputStream()
        val ps = PrintStream(byteArrayOutputStream)
        action(ps)
        ps.flush()
        return byteArrayOutputStream.toString()
    }