1e41f4b71Sopenharmony_ci# Lifecycle 2e41f4b71Sopenharmony_ci 3e41f4b71Sopenharmony_ci 4e41f4b71Sopenharmony_ci## Application lifecycle 5e41f4b71Sopenharmony_ci 6e41f4b71Sopenharmony_ciYou can define the following application lifecycle methods in the **app.js** file. 7e41f4b71Sopenharmony_ci 8e41f4b71Sopenharmony_ci| Attribute | Type | Description | Called When | 9e41f4b71Sopenharmony_ci| --------- | ---------- | -------- | ------------------ | 10e41f4b71Sopenharmony_ci| onCreate | () => void | Listens for application creation.| The application is created.| 11e41f4b71Sopenharmony_ci| onDestroy | () => void | Listens for application destruction.| The application exits.| 12e41f4b71Sopenharmony_ci 13e41f4b71Sopenharmony_ci## Page Lifecycle 14e41f4b71Sopenharmony_ci 15e41f4b71Sopenharmony_ciYou can define the following page lifecycle functions in the **.js** file of the page. 16e41f4b71Sopenharmony_ci 17e41f4b71Sopenharmony_ci> **NOTE** 18e41f4b71Sopenharmony_ci> 19e41f4b71Sopenharmony_ci> To avoid affecting the page switching performance, do not perform complex, time-consuming operations in a lifecycle function. 20e41f4b71Sopenharmony_ci 21e41f4b71Sopenharmony_ci| Attribute | Type | Description | Called When | 22e41f4b71Sopenharmony_ci| --------- | ---------- | ------------ | -------------------------------------- | 23e41f4b71Sopenharmony_ci| onInit | () => void | Listens for page initialization. | Page initialization is complete. This function is called only once in the page lifecycle.| 24e41f4b71Sopenharmony_ci| onReady | () => void | Listens for page creation.| A page is created. This function is called only once in the page lifecycle. | 25e41f4b71Sopenharmony_ci| onShow | () => void | Listens for page display. | The page is displayed. | 26e41f4b71Sopenharmony_ci| onHide | () => void | Listens for page hiding. | The page is hidden. | 27e41f4b71Sopenharmony_ci| onDestroy | () => void | Listens for page destruction. | The page is destroyed. | 28e41f4b71Sopenharmony_ci 29e41f4b71Sopenharmony_ciThe lifecycle functions of page A are called in the following sequence: 30e41f4b71Sopenharmony_ci 31e41f4b71Sopenharmony_ci- Open page A: Call onInit(), onReady(), and onShow() in sequence. 32e41f4b71Sopenharmony_ci- Open page B on page A: onHide() -> onDestroy() 33e41f4b71Sopenharmony_ci- Go back to page A from page B: onInit() -> onReady() -> onShow() 34e41f4b71Sopenharmony_ci- Exit page A: onHide() -> onDestroy() 35e41f4b71Sopenharmony_ci- Hide page A: onHide() 36e41f4b71Sopenharmony_ci- Show background page A on the foreground: onShow() 37e41f4b71Sopenharmony_ci 38e41f4b71Sopenharmony_ci 39
