Untitled

package com.danser.js_test

import android.annotation.SuppressLint
import android.app.Activity
import android.os.Bundle
import android.webkit.JavascriptInterface
import android.webkit.WebView
import kotlinx.android.synthetic.main.activity_main.*
import kotlin.random.Random

class MainActivity : Activity() {

    lateinit var jsExecutor: JSExecutor

    public override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)


        WebView.setWebContentsDebuggingEnabled(true)

        jsExecutor = JSExecutor(this)

        bExecute.setOnClickListener {
            callJavaScriptFunctionAndGetResultBack(333, Random.nextInt(100, 200))
        }
    }

    private fun callJavaScriptFunctionAndGetResultBack(val1: Int, val2: Int) {
        jsExecutor.execute(
            jsCode = JS_CODE,
            methodUrl = "addSomething(%s, %s)",
            params = *arrayOf(val1, val2)
        ) { result ->
            runOnUiThread { tvResult.text = "Callback got val: $result" }
        }
    }
}

private val JS_CODE =
"""
    function addSomething(a, b) {
        console.log('log from javascript');
        return a + b;
    }
"""


class JSExecutor(activity: Activity) {

    private val webView = WebView(activity)
    private val jsInterface: JavaScriptInterface = JavaScriptInterface(activity, webView)

    init {
        initWebView()
    }

    @SuppressLint("SetJavaScriptEnabled")
    private fun initWebView() {
        webView.settings.javaScriptEnabled = true
        webView.addJavascriptInterface(jsInterface, HANDLER_NAME)
    }

    fun execute(jsCode: String, methodUrl: String, vararg params: Any, onResult: (Int) -> Unit) {
        jsInterface.onResult = onResult
        webView.loadUrl(getHtml(jsCode))
        webView.loadUrl(getMethodUrl(methodUrl, *params))
    }

    private fun getMethodUrl(method: String, vararg params: Any): String {
        val methodCall = String.format(method, *params)
        return "javascript:window.$HANDLER_NAME.setResult( $methodCall )"
    }

    private fun getHtml(jsText: String): String =
        """<html><head><script type="text/javascript">function addSomething(a, b) {
        console.log('log from javascript');
        return a + b;
    }</script></head></html>"""

    class JavaScriptInterface(
        private val activity: Activity,
        private val webView: WebView
    ) {
        var onResult: (Int) -> Unit = {}

        @JavascriptInterface
        fun loadURL(url: String) {
            activity.runOnUiThread { webView.loadUrl(url) }
        }

        @JavascriptInterface
        fun setResult(result: Int) {
            onResult(result)
        }
    }

    companion object {
        private const val HANDLER_NAME = "interface handler"
    }

}