# Controllers (iOS) / Fragments (Android)

The SDK can pop controllers above your UI like product presentation pages (see [Promoting In-App Purchases](https://purchasely.gitbook.io/purchasely/advanced-features/promoting-your-products/promoting-in-app-purchases)) or the subscription lists or any deeplink triggered by a push service.

Of course we will wait for you to tell us when we are free to cover your content by calling `isReadyToPurchase` ([more details](https://purchasely.gitbook.io/purchasely/quick-start-1/sdk-configuration/config-appendices#notifying-the-sdk-when-the-app-is-ready-loaded)) but you might want to take control on the controller animation, position… It can be a side bar with the offer on tablets or toaster messages for the error messages.

You can override the default behaviors and implement yours by using the `PLYUIDelegate`.

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

```swift
Purchasely.setUIDelegate(self)
```

{% endtab %}

{% tab title="Objective-C" %}

```objectivec
[Purchasely setUIDelegate:self];
```

{% endtab %}

{% tab title="Kotlin" %}

```kotlin
Purchasely.uiListener = this
```

{% endtab %}

{% tab title="Java" %}

```java
Purchasely.setUiListener(this);
```

{% endtab %}
{% endtabs %}

To change the transition, size, position … of a presented controller (`PLYUIControllerType` gives you the type of controller displayed):

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

```swift
func display(controller: UIViewController, type: PLYUIControllerType) {
	// Present the controller your way
}
```

{% endtab %}

{% tab title="Objective-C" %}

```objectivec
- (void)displayWithController:(UIViewController *)controller type:(enum PLYUIControllerType)type {
	// Present the controller your way
}
```

{% endtab %}

{% tab title="Kotlin" %}

```kotlin
override fun onAlert(alert: PLYAlertMessage) {
    //TODO display alert dialog, see "Errors & alerts" page
}

override fun onView(@NotNull view: View, type: PLYUIViewType) {
    //TODO display view as you wish in your activity
    //type can be PRODUCT_PAGE, SUBSCRIPTION_LIST or CANCELLATION_PAGE
}
```

{% endtab %}

{% tab title="Java" %}

```java
@Override
public void onAlert(@NotNull PLYAlertMessage alert) {
  //TODO display alert dialog, see "Errors & alerts" page
}

@Override
public void onView(@NotNull View view, @NotNull PLYUIViewType type) {
  //TODO display view as you wish in your activity
  //type can be PRODUCT_PAGE, SUBSCRIPTION_LIST or CANCELLATION_PAGE
}
```

{% endtab %}
{% endtabs %}

{% hint style="warning" %}
Android only : We advise you to call `Purchasely.setUiListener(null)`when done to remove all references to your activity if you are not using `WeakReference`
{% endhint %}