# Use WebKitWebViewUIImplementation and UIImplementation

The default behavior of the Authgear Mobile SDKs is to launch AuthUI in [ASWebAuthenticationSession](https://developer.apple.com/documentation/authenticationservices/aswebauthenticationsession) in iOS and [Custom Tabs](https://developer.chrome.com/docs/android/custom-tabs) in Android. The latest versions of the mobile SDKs include `WebKitWebViewUIImplementation` a `UIImplementation` which makes it possible to customize the above behavior. For example, setting the `uiImplementation` attribute in the `configure()` method of the Authgear Capacitor SDK to `WebKitWebViewUIImplementation()` will open AuthUI using [WKWebView](https://developer.apple.com/documentation/webkit/wkwebview) on iOS and [android.webkit.WebView](https://developer.android.com/reference/android/webkit/WebView) on Android.

Omitting the `uiImplementation` attribute in the `configure()` method will fall back to the default behavior (launching  AuthUI in ASWebAuthenticationSession/Custom Tabs). You can also explicitly  choose the default behavior by setting `uiImplementation` to `DeviceBrowserUIImplementation()`.

### Example:  Setting UIImplementation

The following examples show how to set the `uiImplementation`  attribute.

{% tabs %}
{% tab title="Ionic" %}

```typescript
authgearCapacitor.configure({
    clientID: "<CLIENT_ID>",
    endpoint: "<AUTHGEAR_ENDPOINT>",
    isSSOEnabled: true,
    uiImplementation: new WebKitWebViewUIImplementation(),
    tokenStorage: new TransientTokenStorage()
});
```

{% endtab %}

{% tab title="React Native" %}

```typescript
authgear
      .configure({
        clientID: "<CLIENT_ID>",
        endpoint: "<AUTHGEAR_ENDPOINT>",
        uiImplementation: new WebKitWebViewUIImplementation()
      })
```

{% endtab %}

{% tab title="Android" %}

```java
private Authgear authgear = new Authgear(
                                getApplication(),
                                "<CLIENT_ID>",
                                "<AUTHGEAR_ENDPOINT>",
                                tokenStorage,
                                new WebKitWebViewUIImplementation(),
                                isSsoEnabled,
                                null,
                                app2appOptions
                                );
```

{% endtab %}

{% tab title="iOS" %}

```swift
Authgear(
            clientId: "<CLIENT_ID>",
            endpoint: "<AUTHGEAR_ENDPOINT>",
            tokenStorage: tokenStorageInstance,
            uiImplementation: WKWebViewUIImplementation(),
            isSSOEnabled: isSSOEnabled,
            app2AppOptions: app2AppOptions
        )
```

{% endtab %}
{% endtabs %}

Setting `uiImplementation` to `WebKitWebViewUIImplementation` in the above example will change the behavior of your application from the default to using `WKWebView` on iOS and `android.webkit.WebView` on Android.&#x20;

### Customizing the WebKitWebView UI

`WebKitWebViewUIImplementation`  allows you to customize some parts of the UI. You can do this by passing your customization options as parameters in WebKitWebViewUIImplementation(). You can customize the following parts of the UI:

**Android**

* `actionBarBackgroundColor`: Use this option to customize the color of the action bar on the WebView Activity screen. The value should be of type integer according to this encoding: <https://developer.android.com/reference/android/graphics/Color#encoding>
* `actionBarButtonTintColor`: This option can be used to set the color of the icons and texts on the action bar. The value should also be of type integer and use the encoding here: <https://developer.android.com/reference/android/graphics/Color#encoding>.

**iOS**

* `navigationBarBackgroundColor`: This option can be used to customize the color of the navigation bar on iOS. The value should be of type [UIColor](https://developer.apple.com/documentation/uikit/uicolor/) or an integer (React Native or Ionic SDKs) using the following encoding: <https://developer.android.com/reference/android/graphics/Color#encoding>.
* `navigationBarButtonTintColor`: This option sets the color of icons and texts on the navigation bar. The value should also be UIColor or an integer (React Native or Ionic SDKs) using the same encoding as `navigationBarBackgroundColor`.
* `modalPresentationStyle`: Sets the type of modal to be shown. The value can be any of the following: "automatic", "fullScreen", "pageSheet".

The following examples show how to set custom background color, tint color, and modal presentation style.

{% tabs %}
{% tab title="Ionic" %}

```typescript
authgearCapacitor.configure({
  clientID: "<CLIENT_ID>",
  endpoint: "<AUTHGEAR_ENDPOINT>",
  uiImplementation: new WebKitWebViewUIImplementation({
    ios: {
      modalPresentationStyle: "fullScreen"
    },
    android: {
      actionBarBackgroundColor: 0xffffff00,
      actionBarButtonTintColor: 0xff000000
    }
  }),
  tokenStorage: new TransientTokenStorage()
});
```

{% endtab %}

{% tab title="React Native" %}

```typescript
authgear
      .configure({
        clientID: "<CLIENT_ID>",
        endpoint: "<AUTHGEAR_ENDPOINT>",
        uiImplementation: new WebKitWebViewUIImplementation({
          ios: {
            modalPresentationStyle: "fullScreen"
          },
          android: {
            actionBarBackgroundColor: 0xffffff00,
            actionBarButtonTintColor: 0xff000000
          }
        })
      })
```

{% endtab %}

{% tab title="Android" %}

```java
private int actionBarBackgroundColor = 0xffffff00;
private int actionBarButtonTintColor = 0xff000000;
private Authgear authgear = new Authgear(
                                getApplication(),
                                "<CLIENT_ID>",
                                "<AUTHGEAR_ENDPOINT>",
                                tokenStorage,
                                new WebKitWebViewUIImplementation(actionBarBackgroundColor, actionBarButtonTintColor),
                                isSsoEnabled,
                                null,
                                app2appOptions
                                );
```

{% endtab %}

{% tab title="iOS" %}

```swift
Authgear(
            clientId: "<CLIENT_ID>",
            endpoint: "<AUTHGEAR_ENDPOINT>",
            tokenStorage: tokenStorageInstance,
            uiImplementation: WKWebViewUIImplementation(
               modalPresentationStyle: UIModalPresentationStyle.fullScreen,
               navigationBarBackgroundColor: UIColor.yellow,
               navigationBarButtonTintColor: UIColor.black
            ),
            isSSOEnabled: isSSOEnabled,
            app2AppOptions: app2AppOptions
        )
```

{% endtab %}
{% endtabs %}

### Implementing your Custom UIImplementation

You can implement your own custom `UIImplementation` when the `WebKitWebViewUIImplementation` does not meet the requirements of your use case.

The WebKitWebViewUIImplementation class itself is basically a class that implements `UIImplementation` and overrides the `openAuthorizationURL()`method. Hence your custom implementation may look like this:

```typescript
class MyUIImplementation implements UIImplementation {
 async openAuthorizationURL(options: OpenAuthorizationURLOptions):
Promise<string> {
 // Call your own plugin code to implement this.
 }
}
```

Then, you can use your custom implementation like this:

```typescript
authgear.configure({
 clientID: "my_client_id",
 endpoint: "my_endpoint",
 isSSOEnabled: true,
 uiImplementation: new MyUIImplementation(),
})
```

To get a deeper understanding of how to implement your UIImplementation, see the code for the [WebKitWebViewUIImplementation](https://github.com/authgear/authgear-sdk-android/blob/main/sdk/src/main/java/com/oursky/authgear/WebKitWebViewUIImplementation.kt) implementation.

### Unsupported Features and Services

When you drop the default DeviceBrowserUIImplementation to use your own custom UI implementation that uses WebView, it is important to note that you'll be losing the following features and services:

1. **Login with Google:** Google prohibits the use of `WebKitWebView` with the Google SSO. Learn more here: <https://developers.googleblog.com/2021/06/upcoming-security-changes-to-googles-oauth-2.0-authorization-endpoint.html>. As a result `WebKitWebViewUIImplementation` and Google SSO cannot be used together.
2. **Passkey:** Passkey is not supported in WebKitWebView.