Unable to reload Android WebView from Javascript

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心在旅途

I\'m quite new to the Android Development and this behaviour is quite weird or could be a result of a bug.

Project description

I\'m creating an App with a WebV

Test Project

Here is the code of a small Android Activity (Kotlin+XML Layout) that will show the problem. Paste them in an new Android Studio project, press some buttons and check Logcat (filter 'PNK').

MainActivity.kt

package it.punkman.webviewreloadbug

import android.os.AsyncTask
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.view.View
import android.webkit.JavascriptInterface
import android.webkit.WebChromeClient
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    class JSInterface(val mainActivity: MainActivity){

        private inner class Reloader : AsyncTask<Int, Void, Int>() {
            override fun doInBackground(vararg params: Int?): Int {
                Thread.sleep(500)
                return 0
            }

            override fun onPostExecute(result: Int?) {
                super.onPostExecute(result)
                Log.d("PNK","Android - Reload Async Real execute!")
                mainActivity.refreshWebView(mainActivity.btnRefresh)
                Toast.makeText(mainActivity,"WebView refreshed! OK!",Toast.LENGTH_LONG).show(); //OK
            }
        }

        @JavascriptInterface
        fun reloadBug(){
            Log.d("PNK","Android - Reload Bug Start")
            mainActivity.refreshWebView(mainActivity.btnRefresh)
            Log.d("PNK","Android - Reload Bug End")
            Toast.makeText(mainActivity,"You cannot see this toast!",Toast.LENGTH_LONG).show(); //Unable to see
        }

        @JavascriptInterface
        fun reloadAsync(){
            Log.d("PNK","Android - Reload Async Start")
            Reloader().execute(0,null,0)
            Log.d("PNK","Android - Reload Async Stop")
        }
    }

    val HTML_SAMPLE_PAGE="""
       <!DOCTYPE html>
       <html>
         <head>
            <script>
                function refreshPage(){
                    alert("DOM - Refresh Start");
                    location.reload(); //Inside an Android WebView this isn't working!
                    alert("DOM - Refresh End\nNothing refreshed, reload ignored");
                }

                function refreshPageJSI_Bug(){
                    alert("JS Interface - Refresh Start");
                    JSI.reloadBug()
                    alert("JS Interface - Refresh End NEVER SHOWN!"); //NEVER SHOWN!
                }

                function refreshPageJSI_Async(){
                    alert("JS Interface - Refresh Start Async");
                    JSI.reloadAsync()
                    alert("JS Interface - Refresh End Async");
                }
            </script>
         </head>
         <body>
           <script>document.write(new Date())</script>
           <br/><br/>
           <button style="width:100%" onclick="refreshPage()">HTML - JS Refresh</button><br/><br/>
           <button style="width:100%" onclick="refreshPageJSI_Bug()">HTML - JavascriptInterface BUG?</button><br/><br/>
           <button style="width:100%" onclick="refreshPageJSI_Async()">HTML - JavascriptInterface with AsyncTask</button>
         </body>
       </html>
    """

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

        // For the purpose of this example
        // the page is just injected from a string
        // but the result is the same

        testWebView.settings.javaScriptEnabled=true
        testWebView.webChromeClient = WebChromeClient()
        testWebView.addJavascriptInterface( JSInterface(this), "JSI")
        testWebView.loadData(HTML_SAMPLE_PAGE,"text/html",null)
    }

    fun refreshWebView(v:View){
        Log.d("PNK","Android - Refresh Start")
        testWebView.reload()
        // OR again using loadUrl - testWebView.loadUrl(HTML_SAMPLE_PAGE)
        Log.d("PNK","Android - Refresh End")
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">
    <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent" tools:layout_editor_absoluteY="8dp"
            tools:layout_editor_absoluteX="8dp">
        <LinearLayout
                android:orientation="horizontal"
                android:layout_width="match_parent"
                android:layout_height="50dp">
            <Button
                    android:layout_width="match_parent"
                    android:layout_height="50dp"
                    android:onClick="refreshWebView"
                    android:text="Android - Refresh"
                    android:id="@+id/btnRefresh"/>

        </LinearLayout>
        <WebView
                android:layout_width="match_parent"
                android:layout_height="match_parent" android:id="@+id/testWebView"/>
    </LinearLayout>
</android.support.constraint.ConstraintLayout>

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