Crash on Android due to faulty onDestroy() when js->go calls are in flight during destroy

[bafto]

Wails version family

v3

Operating System

Android (experimental)

Description

I encountered a bug where I would get a crash when minimizing the my App on Android:

07-31 16:24:43.096 10758 10758 W cr_AwContents: WebView.destroy() called while WebView is still attached to window.
07-31 16:24:43.100 10758 10758 W WindowOnBackDispatcher: sendCancelIfRunning: isInProgress=false callback=android.view.ViewRootImpl$$ExternalSyntheticLambda14@d9795ca
07-31 16:24:43.105 10758 10758 D ViewRootImpl: Skipping stats log for color mode
07-31 16:24:43.157 10758 10758 W cr_AwContents: Application attempted to call on a destroyed WebView
07-31 16:24:43.157 10758 10758 W cr_AwContents: java.lang.Throwable
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at org.chromium.android_webview.AwContents.p(chromium-SystemWebViewGoogle6432.aab-stable-787112403:10)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at com.android.webview.chromium.WebViewChromium.evaluateJavaScript(chromium-SystemWebViewGoogle6432.aab-stable-787112403:47)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at android.webkit.WebView.evaluateJavascript(WebView.java:895)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at com.wails.app.WailsJSBridge.lambda$sendCallback$1$com-wails-app-WailsJSBridge(WailsJSBridge.java:137)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at com.wails.app.WailsJSBridge$$ExternalSyntheticLambda0.run(D8$$SyntheticClass:0)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at android.os.Handler.handleCallback(Handler.java:1037)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at android.os.Handler.dispatchMessage(Handler.java:108)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at android.os.Looper.loopOnce(Looper.java:304)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at android.os.Looper.loop(Looper.java:430)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at android.app.ActivityThread.main(ActivityThread.java:9345)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at java.lang.reflect.Method.invoke(Native Method)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:593)
07-31 16:24:43.157 10758 10758 W cr_AwContents: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:953)

To Reproduce

In the app I am regularly polling updates from the go backend and I think the bug occured when such a request was in-flight while the View was being destroyed.

Expected behaviour

It should not crash

Screenshots

No response

Attempted Fixes

I am not an expereinced Android native programmer, so I just asked Claude for a quick-fix and that worked for me:

In WailsJSBridge.java:

+    /**
+     * Marks this bridge's WebView as gone. Call before tearing down the
+     * WebView so callbacks from calls already running on {@link #executor}
+     * (e.g. a poll in flight when the Activity is destroyed) no-op instead of
+     * touching a destroyed WebView.
+     */
+    public void markDestroyed() {
+        destroyed = true;
+    }
+
     /**
      * Send a message to Go and return the response synchronously.
      * Called from JavaScript: wails.invoke(message)
@@ -134,7 +148,13 @@ public class WailsJSBridge {
             );
         }
 
-        webView.post(() -> webView.evaluateJavascript(js, null));
+        webView.post(() -> {
+            // Re-checked here, not just by callers before posting: destroy()
+            // can happen in the window between post() and this runnable
+            // actually executing on the UI thread.
+            if (destroyed) return;
+            webView.evaluateJavascript(js, null);
+        });
     }

In MainActivity.java:

@@ -57,6 +58,7 @@ public class MainActivity extends AppCompatActivity {
 
     private WebView webView;
     private WailsBridge bridge;
+    private WailsJSBridge jsBridge;
     // Battery: system-event receivers are registered only while the activity is
     // in the foreground (onStart) and torn down in onStop, so background battery/
     // network/screen broadcasts don't wake the app.
@@ -196,7 +198,8 @@ public class MainActivity extends AppCompatActivity {
         });
 
         // Add JavaScript interface for Go communication
-        webView.addJavascriptInterface(new WailsJSBridge(bridge, webView), "wails");
+        jsBridge = new WailsJSBridge(bridge, webView);
+        webView.addJavascriptInterface(jsBridge, "wails");
     }
 
     private void loadApplication() {
@@ -802,11 +805,26 @@ public class MainActivity extends AppCompatActivity {
     protected void onDestroy() {
         super.onDestroy();
         unregisterSystemEventReceivers();
+        // Mark the JS bridge destroyed before anything else below, so any
+        // invokeAsync call already running on its background executor - e.g.
+        // an in-flight AudioService.Progress() poll - finds the flag set and
+        // skips its evaluateJavascript callback instead of racing destroy().
+        if (jsBridge != null) {
+            jsBridge.markDestroyed();
+        }
         if (bridge != null) {
             bridge.shutdown();
         }
         if (webView != null) {
+            // WebView.destroy() while still attached to the view hierarchy
+            // logs "WebView.destroy() called while WebView is still attached
+            // to window" - detach it first.
+            ViewGroup parent = (ViewGroup) webView.getParent();
+            if (parent != null) {
+                parent.removeView(webView);
+            }
             webView.destroy();
+            webView = null;
         }
     }

But like I said, this is just a quick-and-dirty AI fix that worked for my specific issue, maybe you should look into it in more detail.

System Details

ails v3.0.0-alpha2.117 › Wails Doctor
                                                                                                                                                                                                                                                                                 
# System
        
┌───────────────────────────────────────────────────────────────────────────────┐
| Name                | Linux Mint                                              |
| Version             | 22.1                                                    |
| ID                  | linuxmint                                               |
| Branding            | 22.1 (Xia)                                              |
| Platform            | linux                                                   |
| Architecture        | amd64                                                   |
| Desktop Environment | i3                                                      |
| NVIDIA Driver       | N/A                                                     |
| XDG_SESSION_TYPE    | x11                                                     |
| CPU                 | 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz          |
| GPU                 | TigerLake-LP GT2 [Iris Xe Graphics] (Intel Corporation) |
| Memory              | 15GB                                                    |
└───────────────────────────────────────────────────────────────────────────────┘
                   
# Build Environment
                   
┌──────────────────────────────────────────────────────────────────────┐
| Wails CLI      | v3.0.0-alpha2.117                                   |
| Go Version     | go1.26.5                                            |
| -buildmode     | exe                                                 |
| -compiler      | gc                                                  |
| CGO_CFLAGS     |                                                     |
| CGO_CPPFLAGS   |                                                     |
| CGO_CXXFLAGS   |                                                     |
| CGO_ENABLED    | 1                                                   |
| CGO_LDFLAGS    |                                                     |
| DefaultGODEBUG | cryptocustomrand=1,tlssecpmlkem=0,urlstrictcolons=0 |
| GOAMD64        | v1                                                  |
| GOARCH         | amd64                                               |
| GOOS           | linux                                               |
└──────────────────────────────────────────────────────────────────────┘
              
# Dependencies
              
┌──────────────────────────────────────────────────────────────────────────────────────┐
| *Android NDK            | /home/bafto/Android/Sdk/ndk/29.0.13113456                  |
| *Android SDK            | /home/bafto/Android/Sdk                                    |
| *Android platform-tools | Installed                                                  |
| *Java (Android)         | openjdk version "21.0.11" 2026-04-21                       |
| gcc                     | 12.10ubuntu1                                               |
| gtk3 (legacy)           | 3.24.41-4ubuntu1.3                                         |
| gtk4                    | 4.14.5+ds-0ubuntu0.10                                      |
| npm                     | 11.5.1                                                     |
| pkg-config              | 1.8.1-2build1                                              |
| webkit2gtk (legacy)     | 2.52.3-0ubuntu0.24.04.1                                    |
| webkitgtk-6.0           | 2.52.3-0ubuntu0.24.04.1                                    |
| docker                  | *Docker version 29.7.0, build c1eba93 (daemon not running) |
|                                                                                      |
└────────────────────────────── * - Optional Dependency ───────────────────────────────┘
         
# Signing
         
┌─────────────────────────────────────────────┐
| macOS Signing   | Not configured            |
| Windows Signing | Not configured            |
| Linux Signing   | Not configured            |
└─────────────────────────────────────────────┘
                     
# Checking for issues
                     
 SUCCESS  No issues found
           
# Diagnosis
           
 SUCCESS  Your system is ready for Wails development!

Additional context

No response

[coderabbitai]

🔗 Related PRs

#4435 - fix: prevent crash when closing window with pending async calls [merged]
#4767 - fix: use structured logging for debug/info methods [merged]
#5170 - fix(v3): macOS SingleInstance + URL scheme — relay URL to first instance (#5089) [merged]
#5562 - feat(mobile): iOS and Android support for Wails v3 (experimental) [merged]
#5602 - feat(v3/mobile): IOS/Android manager API + event rename; first-class mobile docs [merged]

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