Build web apps in WebView

Use WebView to deliver a web application or a web page as a part of a client application. The WebView class is an extension of Android's View class that lets you display web pages as a part of your activity layout. It doesn't include the features of a fully developed web browser, such as navigation controls or an address bar. All WebView does, by default, is show a web page.

WebView can help you provide information in your app that you might need to update, such as an end-user agreement or a user guide. Within your Android app, you can create an Activity that contains a WebView, then use it to display your document that's hosted online.

WebView can also help when your app provides data to the user that requires an internet connection to retrieve data, such as email. In this case, you might find that it's easier to build a WebView in your Android app that shows a web page with all the user data, rather than performing a network request, then parsing the data and rendering it in an Android layout. Instead, you can design a web page that's tailored for Android-powered devices and then implement a WebView in your Android app that loads the web page.

This document describes how to get started with WebView, how to bind JavaScript from your web page to client-side code in your Android app, how to handle page navigation, and how to manage windows when using WebView.

Work with WebView on earlier versions of Android

To safely use more-recent WebView capabilities on the device your app is running on, add the AndroidX Webkit library. This is a static library you can add to your application to use android.webkit APIs that aren't available for earlier platform versions.

Add it to your build.gradle file as follows:

Kotlin

dependencies {
    implementation("androidx.webkit:webkit:1.8.0")
}

Groovy

dependencies {
    implementation ("androidx.webkit:webkit:1.8.0")
}

Explore the WebView example on GitHub for more details.

Add a WebView to your app

To add a WebView to your app, you can include the <WebView> element in your activity layout or set the entire Activity window as a WebView in onCreate().

Add a WebView in the activity layout

To add a WebView to your app in the layout, add the following code to your activity's layout XML file:

<WebView
    android:id="@+id/webview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

To load a web page in the WebView, use loadUrl(), as shown in the following example:

Kotlin

val myWebView: WebView = findViewById(R.id.webview)
myWebView.loadUrl("http://www.example.com")

Java

WebView myWebView = (WebView) findViewById(R.id.webview);
myWebView.loadUrl("http://www.example.com");

Add a WebView in onCreate()

To add a WebView to your app in an activity's onCreate() method instead, use logic similar to the following:

Kotlin

val myWebView = WebView(activityContext)
setContentView(myWebView)

Java

WebView myWebView = new WebView(activityContext);
setContentView(myWebView);

Then load the page:

Kotlin

myWebView.loadUrl("http://www.example.com")

Java

myWebView.loadUrl("https://www.example.com");

Or load the URL from an HTML string:

Kotlin

// Create an unencoded HTML string, then convert the unencoded HTML string into
// bytes. Encode it with base64 and load the data.
val unencodedHtml =
     "<html><body>'%23' is the percent code for ‘#‘ </body></html>";
val encodedHtml = Base64.encodeToString(unencodedHtml.toByteArray(), Base64.NO_PADDING)
myWebView.loadData(encodedHtml, "text/html", "base64")

Java

// Create an unencoded HTML string, then convert the unencoded HTML string into
// bytes. Encode it with base64 and load the data.
String unencodedHtml =
     "<html><body>'%23' is the percent code for ‘#‘ </body></html>";
String encodedHtml = Base64.encodeToString(unencodedHtml.getBytes(),
        Base64.NO_PADDING);
myWebView.loadData(encodedHtml, "text/html", "base64");

Your app must have access to the internet. To get internet access, request the INTERNET permission in your manifest file, as shown in the following example:

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

You can customize your WebView by doing any of the following:

Enabling fullscreen support using WebChromeClient. This class is also called when a WebView needs permission to alter the host app's UI, such as creating or closing windows or sending JavaScript dialogs to the user. To learn more about debugging in this context, read Debug web apps.
Handling events that impact content rendering, such as errors on form submissions or navigation using WebViewClient. You can also use this subclass to intercept URL loading.
Enabling JavaScript by modifying WebSettings.
Using JavaScript to access Android framework objects that you have injected into a WebView.

Use JavaScript in WebView

If the web page you want to load in your WebView uses JavaScript, you must enable JavaScript for your WebView. After you enable JavaScript, you can create interfaces between your app code and your JavaScript code.

Enable JavaScript

JavaScript is disabled in a WebView by default. You can enable it through the WebSettings attached to your WebView. Retrieve WebSettings with getSettings(), then enable JavaScript with setJavaScriptEnabled().

See the following example:

Kotlin

val myWebView: WebView = findViewById(R.id.webview)
myWebView.settings.javaScriptEnabled = true

Java

WebView myWebView = (WebView) findViewById(R.id.webview);
WebSettings webSettings = myWebView.getSettings();
webSettings.setJavaScriptEnabled(true);

WebSettings provides access to a variety of other settings that you might find useful. For example, if you're developing a web application that's designed specifically for the WebView in your Android app, then you can define a custom user agent string with setUserAgentString(), then query the custom user agent in your web page to verify that the client requesting your web page is your Android app.

Bind JavaScript code to Android code

When developing a web application that's designed specifically for the WebView in your Android app, you can create interfaces between your JavaScript code and client-side Android code. For example, your JavaScript code can call a method in your Android code to display a Dialog, instead of using JavaScript's alert() function.

To bind a new interface between your JavaScript and Android code, call addJavascriptInterface(), passing it a class instance to bind to your JavaScript and an interface name that your JavaScript can call to access the class.

Warning: Using addJavascriptInterface() lets JavaScript control your Android app. Although this can be useful, it can also be a dangerous security issue. When the HTML in the WebView is untrustworthy—for example, part or all of the HTML is provided by an unknown person or process—then an attacker can include HTML that executes your client-side code and possibly any code of the attacker's choosing. Therefore, don't use addJavascriptInterface() unless you wrote all of the HTML and JavaScript that appears in your WebView. Don't let the user navigate within your WebView to web pages that aren't your own. Instead, let the user's default browser application open foreign links. By default, the user's web browser opens all URL links, so this warning primarily applies if you handle page navigation yourself, as described in the following section.

For example, you can include the following class in your Android app:

Kotlin

/** Instantiate the interface and set the context.  */
class WebAppInterface(private val mContext: Context) {

    /** Show a toast from the web page.  */
    @JavascriptInterface
    fun showToast(toast: String) {
        Toast.makeText(mContext, toast, Toast.LENGTH_SHORT).show()
    }
}

Java

public class WebAppInterface {
    Context mContext;

    /** Instantiate the interface and set the context. */
    WebAppInterface(Context c) {
        mContext = c;
    }

    /** Show a toast from the web page. */
    @JavascriptInterface
    public void showToast(String toast) {
        Toast.makeText(mContext, toast, Toast.LENGTH_SHORT).show();
    }
}

In this example, the WebAppInterface class lets the web page create a Toast message, using the showToast() method.

You can bind this class to the JavaScript that runs in your WebView with addJavascriptInterface(), as shown in the following example:

Kotlin

val webView: WebView = findViewById(R.id.webview)
webView.addJavascriptInterface(WebAppInterface(this), "Android")

Java

WebView webView = (WebView) findViewById(R.id.webview);
webView.addJavascriptInterface(new WebAppInterface(this), "Android");

This creates an interface called Android for JavaScript running in the WebView. At this point, your web application has access to the WebAppInterface class. For example, here's some HTML and JavaScript that creates a toast message using the new interface when the user taps a button:

<input type="button" value="Say hello" onClick="showAndroidToast('Hello Android!')" />

<script type="text/javascript">
    function showAndroidToast(toast) {
        Android.showToast(toast);
    }
</script>

There's no need to initialize the Android interface from JavaScript. The WebView automatically makes it available to your web page. So, when a user taps the button, the showAndroidToast() function uses the Android interface to call the WebAppInterface.showToast() method.

Handle page navigation

When the user taps a link from a web page in your WebView, by default, Android launches an app that handles URLs. Usually, the default web browser opens and loads the destination URL. However, you can override this behavior for your WebView so links open within your WebView. You can then let the user navigate backward and forward through their web page history that's maintained by your WebView.

To open links tapped by the user, provide a WebViewClient for your WebView using setWebViewClient(). All links the user taps load in your WebView. If you want more control over where a clicked link loads, create your own WebViewClient that overrides the shouldOverrideUrlLoading() method. The following example assumes that MyWebViewClient is an inner class of Activity.

Kotlin

private class MyWebViewClient : WebViewClient() {

    override fun shouldOverrideUrlLoading(view: WebView?, url: String?): Boolean {
        if (Uri.parse(url).host == "www.example.com") {
            // This is your website, so don't override. Let your WebView load
            // the page.
            return false
        }
        // Otherwise, the link isn't for a page on your site, so launch another
        // Activity that handles URLs.
        Intent(Intent.ACTION_VIEW, Uri.parse(url)).apply {
            startActivity(this)
        }
        return true
    }
}

Java

private class MyWebViewClient extends WebViewClient {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
        if ("www.example.com".equals(request.getUrl().getHost())) {
      // This is your website, so don't override. Let your WebView load the
      // page.
      return false;
    }
    // Otherwise, the link isn't for a page on your site, so launch another
    // Activity that handles URLs.
    Intent intent = new Intent(Intent.ACTION_VIEW, request.getUrl());
    startActivity(intent);
    return true;
  }
}

Then create an instance of this new WebViewClient for the WebView:

Kotlin

val myWebView: WebView = findViewById(R.id.webview)
myWebView.webViewClient = MyWebViewClient()

Java

WebView myWebView = (WebView) findViewById(R.id.webview);
myWebView.setWebViewClient(new MyWebViewClient());

Now when the user taps a link, the system calls the shouldOverrideUrlLoading() method, which checks whether the URL host matches a specific domain, as defined in the preceding example. If it does match, then the method returns false and doesn't override the URL loading. It lets the WebView load the URL as usual. If the URL host doesn't match, then an Intent is created to launch the default Activity for handling URLs, which resolves to the user's default web browser.

Handle custom URLs

WebView applies restrictions when requesting resources and resolving links that use a custom URL scheme. For example, if you implement callbacks such as shouldOverrideUrlLoading() or shouldInterceptRequest(), then WebView invokes them only for valid URLs.

For example, WebView might not call your shouldOverrideUrlLoading() method for links like this:

<a href="showProfile">Show Profile</a>

Invalid URLs, like the one shown in the preceding example, are handled inconsistently in WebView, so we recommend using a well-formed URL instead. You can use a custom scheme or an HTTPS URL for a domain that your organization controls.

Instead of using a simple string in a link, as in the previous example, you can use a custom scheme such as the following:

<a href="example-app:showProfile">Show Profile</a>

You can then handle this URL in your shouldOverrideUrlLoading() method like this:

Kotlin

// The URL scheme must be non-hierarchical, meaning no trailing slashes.
const val APP_SCHEME = "example-app:"

override fun shouldOverrideUrlLoading(view: WebView?, url: String?): Boolean {
    return if (url?.startsWith(APP_SCHEME) == true) {
        urlData = URLDecoder.decode(url.substring(APP_SCHEME.length), "UTF-8")
        respondToData(urlData)
        true
    } else {
        false
    }
}

Java

// The URL scheme must be non-hierarchical, meaning no trailing slashes.
private static final String APP_SCHEME = "example-app:";

@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
    if (url.startsWith(APP_SCHEME)) {
        urlData = URLDecoder.decode(url.substring(APP_SCHEME.length()), "UTF-8");
        respondToData(urlData);
        return true;
    }
    return false;
}

The shouldOverrideUrlLoading() API is primarily intended for launching intents for specific URLs. When implementing it, make sure to return false for URLs the WebView handles. You aren't limited to launching intents, though. You can replace launching intents with any custom behavior in the preceding code samples.

Navigate web page history

When your WebView overrides URL loading, it automatically accumulates a history of visited web pages. You can navigate backward and forward through the history with goBack() and goForward().

For example, the following shows how your Activity can use the device Back button to navigate backward:

Kotlin

override fun onKeyDown(keyCode: Int, event: KeyEvent?): Boolean {
    // Check whether the key event is the Back button and if there's history.
    if (keyCode == KeyEvent.KEYCODE_BACK && myWebView.canGoBack()) {
        myWebView.goBack()
        return true
    }
    // If it isn't the Back button or there isn't web page history, bubble up to
    // the default system behavior. Probably exit the activity.
    return super.onKeyDown(keyCode, event)
}

Java

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    // Check whether the key event is the Back button and if there's history.
    if ((keyCode == KeyEvent.KEYCODE_BACK) && myWebView.canGoBack()) {
        myWebView.goBack();
        return true;
    }
    // If it isn't the Back button or there's no web page history, bubble up to
    // the default system behavior. Probably exit the activity.
    return super.onKeyDown(keyCode, event);
}

If you app uses AndroidX AppCompat 1.6.0+, you can simplify the previous snippet even more:

Kotlin

onBackPressedDispatcher.addCallback {
    // Check whether there's history.
    if (myWebView.canGoBack()) {
        myWebView.goBack()
    }
}

Java

onBackPressedDispatcher.addCallback {
    // Check whether there's history.
    if (myWebView.canGoBack()) {
        myWebView.goBack();
    }
}

The canGoBack() method returns true if there is web page history for the user to visit. Likewise, you can use canGoForward() to check whether there is a forward history. If you don't perform this check, then after the user reaches the end of the history, goBack() and goForward() do nothing.

Handle device configuration changes

During runtime, activity state changes occur when a device's configuration changes, such as when users rotate the device or dismiss an input method editor (IME). These changes cause a WebView object's activity to be destroyed and a new activity to be created, which also creates a new WebView object that loads the destroyed object's URL. To modify your activity's default behavior, you can change how it handles orientation changes in your manifest. To learn more about handling configuration changes during runtime, read Handle configuration changes.

Manage windows

By default, requests to open new windows are ignored. This is true whether they are opened by JavaScript or by the target attribute in a link. You can customize your WebChromeClient to provide your own behavior for opening multiple windows.

To keep your app more secure, it's best to prevent popups and new windows from opening. The safest way to implement this behavior is to pass "true" into setSupportMultipleWindows() but not override the onCreateWindow() method, which setSupportMultipleWindows() depends on. This logic prevents any page that uses target="_blank" in its links from loading.