using getWebViewLooper API for Android 28+

android/src/main/java/com/pichillilorenzo/flutter_inappwebview/JavaScriptBridgeInterface.java

@@ -35,7 +35,7 @@ public class JavaScriptBridgeInterface {
       return;
     }
 
-    final Handler handler = new Handler(Looper.getMainLooper());
+    final Handler handler = new Handler(inAppWebView.getWebViewLooper());
     handler.post(new Runnable() {
       @Override
       public void run() {
@@ -58,7 +58,7 @@ public class JavaScriptBridgeInterface {
 
     // java.lang.RuntimeException: Methods marked with @UiThread must be executed on the main thread.
     // https://github.com/pichillilorenzo/flutter_inappwebview/issues/98
-    final Handler handler = new Handler(Looper.getMainLooper());
+    final Handler handler = new Handler(inAppWebView.getWebViewLooper());
     handler.post(new Runnable() {
       @Override
       public void run() {

android/src/main/java/com/pichillilorenzo/flutter_inappwebview/content_blocker/ContentBlockerHandler.java

@@ -97,7 +97,7 @@ public class ContentBlockerHandler {
                 final String[] webViewUrl = new String[1];
                 if (!trigger.getLoadType().isEmpty() || !trigger.getIfTopUrl().isEmpty() || !trigger.getUnlessTopUrl().isEmpty()) {
                     final CountDownLatch latch = new CountDownLatch(1);
-                    Handler handler = new Handler(Looper.getMainLooper());
+                    Handler handler = new Handler(webView.getWebViewLooper());
                     handler.post(new Runnable() {
                         @Override
                         public void run() {
@@ -160,7 +160,7 @@ public class ContentBlockerHandler {
                                 "   d.addEventListener('DOMContentLoaded', function(event) { hide(); }); " +
                                 "})(document);";
 
-                        final Handler handler = new Handler(Looper.getMainLooper());
+                        final Handler handler = new Handler(webView.getWebViewLooper());
                         handler.post(new Runnable() {
                             @Override
                             public void run() {

android/src/main/java/com/pichillilorenzo/flutter_inappwebview/in_app_webview/InAppWebView.java

@@ -133,7 +133,7 @@ final public class InAppWebView extends InputAwareWebView implements InAppWebVie
   public LinearLayout floatingContextMenu = null;
   @Nullable
   public Map<String, Object> contextMenu = null;
-  public Handler mainLooperHandler = new Handler(Looper.getMainLooper());
+  public Handler mainLooperHandler = new Handler(getWebViewLooper());
   static Handler mHandler = new Handler();
 
   public Runnable checkScrollStoppedTask;
@@ -1672,6 +1672,14 @@ final public class InAppWebView extends InputAwareWebView implements InAppWebVie
     webMessageListeners.clear();
   }
 
+  @Override
+  public Looper getWebViewLooper() {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+      return super.getWebViewLooper();
+    }
+    return Looper.getMainLooper();
+  }
+
   @Override
   public void postWebMessage(com.pichillilorenzo.flutter_inappwebview.types.WebMessage message, Uri targetOrigin, ValueCallback<String> callback) throws Exception {
     throw new UnsupportedOperationException();

android/src/main/java/com/pichillilorenzo/flutter_inappwebview/types/InAppWebViewInterface.java

@@ -3,6 +3,7 @@ package com.pichillilorenzo.flutter_inappwebview.types;
 import android.content.Context;
 import android.net.Uri;
 import android.net.http.SslCertificate;
+import android.os.Looper;
 import android.webkit.ValueCallback;
 import android.webkit.WebMessage;
 import android.webkit.WebView;
@@ -98,4 +99,5 @@ public interface InAppWebViewInterface {
   void setWebMessageChannels(Map<String, WebMessageChannel> webMessageChannels);
   void disposeWebMessageChannels();
   void disposeWebMessageListeners();
+  Looper getWebViewLooper();
 }

example/integration_test/webview_flutter_test.dart

@@ -5271,6 +5271,10 @@ setTimeout(function() {
         expect(await AndroidInAppWebViewController.getCurrentWebViewPackage(),
             isNotNull);
       }, skip: !Platform.isAndroid);
+
+      test('setWebContentsDebuggingEnabled', () async {
+        expect(AndroidInAppWebViewController.setWebContentsDebuggingEnabled(true), completes);
+      }, skip: !Platform.isAndroid);
     }, skip: !Platform.isAndroid);
 
     group('ios methods', () {