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https://issues.apache.org/jira/browse/CB-12815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16013887#comment-16013887
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Rich Storm commented on CB-12815:
---------------------------------
Possible solution. Instead of setTimeout, use a Promise that resolves
immediately.
Promise.resolve(cordova.callbackFromNative(callbackId, success, status, args,
keepCallback));
> WKWebView plugin will not execute Javascript while app is backgrounded
> ----------------------------------------------------------------------
>
> Key: CB-12815
> URL: https://issues.apache.org/jira/browse/CB-12815
> Project: Apache Cordova
> Issue Type: Bug
> Components: cordova-plugin-wkwebview-engine
> Environment: iOS
> Reporter: Rich Storm
> Assignee: Shazron Abdullah
> Labels: Background, Javascript, WKWebView
>
> iOS 10 now has power saving requirements and will not allow background tasks
> to function to save battery. For example, a VoIP app can no longer use a
> polling strategy to stay awake. The new recommended way, according to Apple
> (https://developer.apple.com/library/content/documentation/Performance/Conceptual/EnergyGuide-iOS/OptimizeVoIP.html),
> is to use VoIP silent push notifications to wake up the app and do the work.
> I have verified that all VoIP silent push notifications arrive correctly when
> using the UIWebView with a vanilla Cordova install. However, when adding the
> cordova-plugin-wkwebview-engine, the Javascript callbacks do not fire
> correctly when receiving the VoIP silent push notification while the app is
> in the background. What happens is the first notification is queued, then the
> next notification forces the first notification result to the callback.
> Effectively, making each push notification 1 behind. When the app is put back
> into the foreground, the last push notification callback is fired.
> When the app is in the foreground, all works fine.
> The issue is with the call to "setTimeout" in the iOSExec.nativeCallback
> function. It makes sense that if Apple is trying to minimize background
> execution to save battery, then they would limit the use of the setTimeout
> feature.
> This issue is fixed by changing the iOSExec.nativeCallback function to call
> the cordova.callbackFromNative function directly without a setTimeout
> wrapper. I understand that removing setTimeout is not an elegant solution and
> may cause deadlocks. Maybe a new argument isBackground or something to that
> effect.
> src/www/ios/ios-wkwebview-exec.js
> {code:javascript}
> iOSExec.nativeCallback = function(callbackId, status, message,
> keepCallback, debug) {
> var success = status === 0 || status === 1;
> var args = convertMessageToArgsNativeToJs(message);
>
> // setTimeout(function(){
> cordova.callbackFromNative(callbackId, success, status, args,
> keepCallback);
> // }, 0);
> };
> {code}
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