Working with the WebView

Overview

If you want to deliver a web application (or just a web page) as a part of a client application, you can do it using WebView. The WebView class is an extension of Android's View class that allows you to display web pages as a part of your activity layout. Since Android 4.4, it is based on the Chrome on Android v33.0.0 according to this reference.

This document shows you how to get started with WebView and how to do some additional things, such as handle page navigation and bind JavaScript from your web page to client-side code in your Android application. See the official WebView docs for a more detailed look.

An alternative for using WebViews is Chrome Custom Tabs, which provides more flexibility in terms of customizing the toolbar, adding animations, or warming up the browser ahead of time. Chrome Custom Tabs only works if Chrome on Android is installed on the browser. For more information, see this guide.

Usage

Load External Pages

To get Internet access, request the INTERNET permission in your manifest file. For example:

<manifest ... >
    <uses-permission android:name="android.permission.INTERNET" />
    ...
</manifest>

To add a WebView to your Application, simply include the <WebView> element in your activity layout:

<?xml version="1.0" encoding="utf-8"?>
<WebView  xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/webview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

First, we need to configure the WebView to behave with reasonable defaults using WebSettings and creating a WebViewClient:

public class MainActivity extends Activity {
   private WebView myWebView;

   @Override		
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      myWebView = (WebView) findViewById(R.id.webview);
      // Configure related browser settings
      myWebView.getSettings().setLoadsImagesAutomatically(true);
      myWebView.getSettings().setJavaScriptEnabled(true);
      myWebView.setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY);
      // Configure the client to use when opening URLs
      myWebView.setWebViewClient(new MyBrowser());
      // Load the initial URL
      myWebView.loadUrl("http://www.example.com");
   }
   
   // Manages the behavior when URLs are loaded
   private class MyBrowser extends WebViewClient {
      @SuppressWarnings("deprecation")
      @Override
      public boolean shouldOverrideUrlLoading(WebView view, String url) {
          view.loadUrl(url);
          return true;
      }

      @TargetApi(Build.VERSION_CODES.N)
      @Override
      public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
          view.loadUrl(request.getUrl().toString());
          return true;
      }
   }
}

You can attach javascript functions and use them within the mobile webpages as described here in the official docs.

Handling responsive layouts

By default, the WebView does not account for the default scale size if HTML pages include viewport metadata. If you wish to enable the page to load with responsive layouts, you need to set it explicitly:

// Enable responsive layout
myWebView.getSettings().setUseWideViewPort(true);
// Zoom out if the content width is greater than the width of the viewport
myWebView.getSettings().setLoadWithOverviewMode(true);

You can also enable the ability to zoom-in controls on the page:

myWebView.getSettings().setSupportZoom(true);
myWebView.getSettings().setBuiltInZoomControls(true); // allow pinch to zooom
myWebView.getSettings().setDisplayZoomControls(false); // disable the default zoom controls on the page

Loading Local Pages

In case you want to store a copy of a webpage locally to be loaded into a WebView, you can put it in the android assets folder. If you do not find one under your main/ directory, then you can create one. Place the html, css, js, etc in this folder.

For example, say I wanted to load a page entitled index.html. I would create my file under {ProjectName}/app/src/main/assets/index.html

then, in your activity or fragment you can use the code

public class MainActivity extends Activity {
   private WebView myWebView;

   @Override		
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      myWebView = (WebView) findViewById(R.id.webview);
      myWebView.getSettings().setJavaScriptEnabled(true);
      myWebView.setWebViewClient(new WebViewClient());
      String path = Uri.parse("file:///android_asset/index.html").toString();
      myWebView.loadUrl(path);
   }

}

Sharing cookies between WebViews and networking clients

WebViews currently use their own cookie manager, which means that any network requests you make outside of these web views are usually stored separately. This can cause problems when trying to retain the same cookies (i.e. for authentication or cross-site script forgery (CSRF) headers). The simplest approach as proposed in this Stack Overflow article is to implement a cookie handler that forwards all requests to the WebView cookie store. See this gist for an example.

References

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