You may have noticed that you can follow other links within the WebView once you launch PhotoPageActivity. However, no matter how many links you follow, the Back button always brings you immediately back to PhotoGalleryActivity. What if you instead want the Back button to bring users through their browsing history within the WebView?
Implement this behavior by overriding the Back button method Activity.onBackPressed(). Within that method you can use a combination of WebView’s browsing history methods (WebView.canGoBack() and WebView.goBack()) to do the right thing. If there are items in the WebView’s browsing history, go back to the previous item. Otherwise, allow the Back button to behave as normal by calling through to super.onBackPressed().