Elements of the Application Model

The application model is the abstraction of capabilities required by OpenHarmony applications. It provides necessary components and running mechanisms for applications. With application models, you can develop applications based on a unified set of models, making application development simpler and more efficient.

The OpenHarmony application model consists of the following elements:

• Application component

  An application component is the basic unit and running entry of an application. When a user starts, uses, or exits an application, the application component transits in different states. This is called the application component lifecycle. The application component provides lifecycle callback functions, through which you can detect application status changes. When compiling an application, you needs to compile application components and their lifecycle callback functions, and configure related information in the application configuration file. In this way, the operating system creates an application component instance based on the configuration file during running, and schedules the lifecycle callback functions, so as to execute your code.

• Application process model

  The application process model defines how application processes are created, destroyed, and communicate with each other.

• Application thread model

  The application thread model defines how a thread in an application process is created and destroyed, how the main thread and UI thread are created, and how the threads communicate with each other.

• Application mission management model

  The application mission management model defines how a mission is created and destroyed, and the relationship between missions and components. A mission is a record about the use of an application component instance. Each time a user starts an application component instance, a mission is generated. For example, when a user starts a video application, the video application mission is displayed on the Recents page. When the user clicks the mission, the system switches the mission to the foreground. If the video editing functionality in the video application is compiled by using an application component, an application component instance for video editing is created when the user starts video editing. In this case, both the video application mission and video editing mission are displayed on the Recents page.

• Application configuration file

  The application configuration file contains information about the application configuration, application components, and permissions, as well as custom information. The information will be provided for the compiler, application market, and operating system in the build, distribution, and running phases.