Application life cycle and page life cycle of applets

1. Application life cycle

The process of applet from start->run->destroy

Application lifecycle functions

Application lifecycle functions are declared in app.js, and the execution sequence is as follows

• onLaunch (triggered when the applet is initialized, only triggered once globally, and executed before all page cycle functions)
• onShow (triggered when the applet starts, or enters the foreground display from the background, and executes before all page cycle functions)
• onHide (triggered when the applet enters the background display from the foreground)
• onError (triggered when a script error occurs in the applet or an error is reported in an API call)
• onPageNotFound (triggered when the page to be opened by the applet does not exist)
• onUnhandledRejection (triggered when the applet has an unhandled Promise rejection)
• onThemeChange (triggered when the system switches the theme)

2. Page life cycle

Each page load->render->destroy process

Page lifecycle functions

The page life cycle function is declared in the .js file of the page, and the execution sequence is as follows

• onLoad (executed when the page is created, only called once in a page life cycle, can receive an object parameter, which contains the wx.navigateTo()parameters spliced ​​​​in the url when the page is opened, often used for initialization and dumping data)

  ①It is executed when the page displayed when the applet is opened

  ② It is executed when wx.navigateTothe opened

  ③It is called and executed when the page is opened wx.switchTabfor the first time

• onShow (executed when the page appears in the foreground)

• onReady (executed when the page is rendered for the first time, monitor the completion of the first rendering of the page, and only call once in a page life cycle, you can modify the page content in this function, such as calling wx.setNavigationBarTitle)

  ①It is executed when the page displayed when the applet is opened

  ② It is executed when wx.navigateTothe opened

  ③It is called and executed when the page is opened wx.switchTabfor the first time

• onHide (the page is not closed, it is only executed when it changes from the foreground to the background)

  ① Normal page use Execute when wx.navigateToswitching to other pages

  ②The tabBar page is used to execute when wx.switchTabswitching to other pages

• onUnload (executed when the page is destroyed, only called once in a page life cycle)

• onPullDownRefresh (executed when pull-down refresh is triggered)

• onReachBottom (executed when the page bottoms out)

• onShareAppMessage (executed when the page is shared by the user)

• onPageScroll (executed when the page scrolls)

• onResize (executed when the page size changes)

• onTabItemTap (when the current tabBar page is triggered when the tab is clicked, if a custom tabbar is used, it will not be triggered. An object parameter can be received, which contains the index, pagePath, text and other data of the clicked tab)

Note:

​ ① wx.switchTabWhen calling (only jump to the tabBar page ), close all other non-tabBar pages , that is, execute all non-tabBar unclosed pagesonUnload

​ ② wx.reLaunchWhen , all unclosed pages will be closed (including the current page), that is, all unclosed pages will executeonUnload

​ ③ wx.redirectToWhen (can only jump to non-tabBar pages ), the current page is closed and the current page is executedonUnload

​ ④ wx.navigateToWhen , save the current page (use wx.navigateBackto return), and jump to a page in the application. But you can't jump to the tabbar page, the current page executesonHide

​ ⑤ When calling wx.navigateBack(returning to the previous page or multi-level page), all pop-up pages between the current page (including the current page) and the target page are closed , and the executiononUnload