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Detect use of Android back button using JavaScript

Posted by: admin May 14, 2020 Leave a comment

Questions:

My site has breadcrumbs which highlight which stage in a process the user has reached. The breadcrumbs rely on the browser history to tell which stage should be highlighted when the browser back button is used, but on Android devices using the hardware back button this seems to be bypassed and the highlighted breadcrumb does not change.

My site is not using PhoneGap or anything similar as it’s not usually a mobile site, so is it possible to capture use of the Android back button so that I can add an event to set the breadcrumb highlight based on the history log when the button is used, just using JavaScript or jQuery?

How to&Answers:

1. Use popstate event.

https://developer.mozilla.org/en-US/docs/Web/Events/popstate

window.onpopstate = function(e) { 
   updateBreadCrumbObservable();
};

2. Use onhashchange event.

window.onhashchange = function(e) {
   updateBreadCrumbObservable();
}

You can use event argument to get more description about the event fired.

Answer:

You can put check on inside onBackPressed method of the activity and before calling super.onBackPressed(); trigger the method to call javascript method.

for e.g:

override fun onBackPressed() {
    if (handleBackPress) {
        myWebView.loadUrl("javascript:backButtonPressed()")
    }else {
        super.onBackPressed()
    }
}

in the above example if handleBackPress boolean variable is true, then it will try to call backButtonPressed() method of javascript file in the webview.

Let me know if you need any explanation or help.