How to check if variable value is Changed in other thread in Kotlin?

Issue

I am trying to change my Variable inside my WebViewClient but my Function don't wait for page to load. I think It is because WebView has its own thread. If that is the case then how can I pause my function to wait for page. or is there any other method to keep the value in my Function?

private fun getNewUrl(url: String): String {
    var newUrl = "null"
    val webView = WebView(applicationContext)

    webView.webViewClient = object : WebViewClient() {
        override fun onPageFinished(view: WebView?, url: String?) {
           super.onPageFinished(view, url)
           Toast.makeText(applicationContext, "Page Loaded", Toast.LENGTH_SHORT).show()
           newUrl = url.toString()
       }
   }

   webView.loadUrl(url)
   return newUrl
}

Solution

Yes. Because that call happens Asynchronously. It doesn't block the execution of following lines.

So you need to have your listener class called when that result is loaded & use that result.

For example:

Create an interface:

interface OnPageLoadedListener {

    fun onLoaded(url: String)
} 

Pass it as an argument to your function:

private fun getNewUrl(url: String, onPageLoadedListener: OnPageLoadedListener) {
        var newUrl: String
        val webView = WebView(applicationContext)
        webView.webViewClient = object : WebViewClient() {
            override fun onPageFinished(view: WebView?, url: String?) {
                super.onPageFinished(view, url)
                Toast.makeText(applicationContext, "Page Loaded", Toast.LENGTH_SHORT).show()
                pageUrl = url.toString()
                newUrl = url.toString()
                onPageLoadedListener.onLoaded(newUrl)
            }
        }
        webView.loadUrl(url)
    }

Call your function:

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        getNewUrl("https://www.google.com/", object : OnPageLoadedListener {
            override fun onLoaded(url: String) {
                Toast.makeText(applicationContext, url, Toast.LENGTH_SHORT).show()
            }
        })
    }

Answered By - Mayur Gajra