Atomic Service Full Screen Launch Component (FullScreenLaunchComponent)

With the FullScreenLaunchComponent component, you can launch atomic services in full screen mode, providing a more native and user-friendly experience within applications.

Basic Concepts

• FullScreenLaunchComponent component

Provided by ArkUI, FullScreenLaunchComponent is a component that allows you to define and use it in your application through the ArkTS-based declarative development paradigm. This component is encapsulated based on UIExtension, but unlike the system API UIExtensionComponent, it grants usage permissions to third-party applications. If the atomic service to be launched grants permission for full-screen embedding, the host application can run the atomic service in full-screen embedded mode. Without permission, the application will launch the atomic service in a separate, pop-up mode.

• EmbeddableUIAbility component

Defined and used in the provider application, UIExtensionAbility allows the provider to run in a separate process. It offers two launch modes: one for redirecting to the provider and another for embedding the provider directly within the application.

Implementation Principles

FullScreenLaunchComponent offers the capability to launch atomic services in full-screen mode. When an atomic service needs to be launched, the AMS checks whether the provider has authorized the host application to run the atomic service in an embedded manner. If authorization is granted, the host application runs the atomic service in full-screen embedded mode; otherwise, the host application launches the atomic service in a separate, pop-up mode.

Running an atomic service in full-screen embedded mode means to embed it into the host application’s component tree using UIExtensionComponent and, by launching the EmbeddableUIAbility, display the content of the provider, offering a seamless, component-based interaction experience.

Launching an atomic service in a separate, pop-up mode means to launch the EmbeddableUIAbility outside of the component hierarchy, offering an interaction experience similar to that of a standalone window.

Available Capabilities

Basic Component Capabilities

• When the service provider authorizes the host application to run the atomic service in an embedded manner, the host application runs the atomic service EmbeddableUIAbility in full-screen embedded mode.
• When the service provider does not authorize the host application to run the atomic service in an embedded manner, the host application launches the atomic service EmbeddableUIAbility in a separate, pop-up mode.
• You can customize an icon placeholder component, which, when touched, launches the atomic service.

Available Capabilities of the EmbeddableUIAbility Process

The FullScreenLaunchComponent is designed to facilitate the sharing of capabilities across different applications, offering a high degree of flexibility. It operates by launching the provider application’s capabilities through a cross-process approach for use by the current (host) application. This mechanism involves service interactions between two separate processes, which is fundamentally different from the interactions between common components and their host applications.

Below is a detailed list of the attributes, events, components, Node-APIs, and other features that the provider application can utilize within the FullScreenLaunchComponent.

This list specifies the features that are not supported and those that are partially supported.

Universal Attributes

The universal attributes are not supported.

Components

By default, the provider application cannot interact with the host application’s components or process context. Specifically, the following are not supported:

• Effects that exceed a component’s boundaries, such as the Navigation component displaying into the safe area
• Components that rely on other components or require cross-component or cross-application control and access, for example, PluginComponent for accessing other components or FormComponent for displaying pages from other applications across processes
• Components that depend on the host application’s window information or process UIContext instance for capabilities, interactions, or animations, such as the FolderStack component

The details are as follows.

Node-API

The capabilities provided by Node-APIs in the FullScreenLaunchComponent scenario must account for their potential to extend beyond the current component and interact with the host application’s components and process context. Specifically, the following are not supported:

• The API may require information from the host application’s context or window, such as UIContext.
• The API may control or influence not just the component itself but also other components or aspects of the host application, such as UI appearance.

The details are as follows.

Constraints

Security Capability Constraints

The FullScreenLaunchComponent (on the host) can access applications that have integrated the EmbeddableUIAbility (on the provider side), offering a universal capability for application sharing. As capabilities of the FullScreenLaunchComponent do not independently include a security mechanism, the provider application must utilize other ArkUI capabilities to protect against potential attacks from the host application.

Considering the extensive capabilities of the FullScreenLaunchComponent, if there are security concerns within the provider application that cannot be resolved within the FullScreenLaunchComponent, alternative approaches should be considered. Using the FullScreenLaunchComponent without proper security measures poses potential risks to both the provider and host applications.

Usage modes:

• When the service provider authorizes the host application to run the atomic service in an embedded manner, the host application runs the atomic service in full-screen embedded mode.
• When the service provider does not authorize the host application to run the atomic service in an embedded manner, the host application runs the atomic service in a separate, pop-up mode.

The full-screen embedded mode restricts the host application’s interaction capabilities, as it can no longer create subwindows that could cover the provider application’s window.

Nesting Constraints

The FullScreenLaunchComponent does not allow for a nested dependency chain, for example, application A (UIAbility) -> application B (EmbeddableUIAbility) -> application C (EmbeddableUIAbility).

Event Processing Mechanism Constraints

The FullScreenLaunchComponent does not support the universal events. Instead, it passes events to the provider’s EmbeddableUIAbility after coordinate transformation.

Events are handled synchronously or asynchronously based on their use case:

• Interactions between the host process and the provider process are handled asynchronously by default: This avoids performance issues and deadlocks, which could affect the overall interaction experience.
• Synchronous event handling principles: Synchronous events are supported where they have a low trigger frequency and minimal performance impact; they should meet the actual use scenarios.

When using the FullScreenLaunchComponent, comply with the following design constraints:

Asynchronous event handling scenarios: Both the FullScreenLaunchComponent component and the host application’s components may receive events simultaneously. You need to manage this based on the use scenario. For example, you can configure the host application components not to handle the events. If this is not feasible, you are advised to replace the FullScreenLaunchComponent component to ensure a seamless interaction experience.

Page Rendering Experience Constraints

As the FullScreenLaunchComponent involves cross-process application calls, the processing between the host application process and the provider application process cannot be synchronized, leading to different experience issues compared to regular components. Be aware of the performance constraints of rendering pages across multiple processes with this component and take targeted measures.

• Flickering white screen: Initiating a new process through the FullScreenLaunchComponent to deliver functionality involves a sequence of steps – creation, launch, and page rendering – that require time to complete. During this period, users may notice a brief display of the FullScreenLaunchComponent’s default white background, resulting in a flickering white screen.
• Desynchronization between rendering and display: When the host application page changes rapidly (such as during screen rotation or window resizing), there can be a desynchronization between the rendering of the host application page and the content displayed within the FullScreenLaunchComponent component. This issue arises from cross-process interactions; while the provider application’s process tasks are triggered by the host application, layout tasks are handled in the respective process’s JavaScript thread. There is no guarantee of synchronization between the host application’s and provider application’s rendering tasks, resulting in desynchronization.

When developing the provider application, consider the following design constraints:

• Use scenarios with minimal layout changes.
• When layout changes occur, the provider application’s JavaScript thread should execute as few tasks as possible to ensure that it can respond to layout change tasks promptly.

You can mitigate the flickering white screen issue with the provider application in the following ways:

• Adjust the background color of the FullScreenLaunchComponent (for instructions, see Background) to match the background color of the host application’s and provider application’s pages, to deliver a seamless transition and prevent noticeable changes during the loading process.

If the mitigation does not fully meet the application’s interaction requirements due to the constraints of cross-process capabilities, it is recommended that you consider alternative solutions.

Other Constraints

• Modifying or switching the atomic service EmbeddableUIAbility launched from the background is not supported during runtime.

• This component cannot be previewed from the DevEco Studio Previewer.

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