Xamarin.Forms 生命週期不是實際的應用程式生命週期，而是它的跨平臺表示

讓我們看看不同平臺的本機應用程式生命週期方法。

Android 系統

//Xamarin.Forms.Platform.Android.FormsApplicationActivity lifecycle methods:
protected override void OnCreate(Bundle savedInstanceState);
protected override void OnDestroy();
protected override void OnPause();
protected override void OnRestart();
protected override void OnResume();
protected override void OnStart();
protected override void OnStop();

iOS 版

//Xamarin.Forms.Platform.iOS.FormsApplicationDelegate lifecycle methods:
public override void DidEnterBackground(UIApplication uiApplication);
public override bool FinishedLaunching(UIApplication uiApplication, NSDictionary launchOptions);
public override void OnActivated(UIApplication uiApplication);
public override void OnResignActivation(UIApplication uiApplication);
public override void WillEnterForeground(UIApplication uiApplication);
public override bool WillFinishLaunching(UIApplication uiApplication, NSDictionary launchOptions);
public override void WillTerminate(UIApplication uiApplication);

Windows

//Windows.UI.Xaml.Application lifecycle methods:
public event EventHandler<System.Object> Resuming;
public event SuspendingEventHandler Suspending;    
protected virtual void OnActivated(IActivatedEventArgs args);
protected virtual void OnFileActivated(FileActivatedEventArgs args);
protected virtual void OnFileOpenPickerActivated(FileOpenPickerActivatedEventArgs args);
protected virtual void OnFileSavePickerActivated(FileSavePickerActivatedEventArgs args);
protected virtual void OnLaunched(LaunchActivatedEventArgs args);
protected virtual void OnSearchActivated(SearchActivatedEventArgs args);
protected virtual void OnShareTargetActivated(ShareTargetActivatedEventArgs args);
protected virtual void OnWindowCreated(WindowCreatedEventArgs args);

//Windows.UI.Xaml.Window lifecycle methods:
public event WindowActivatedEventHandler Activated;
public event WindowClosedEventHandler Closed;
public event WindowVisibilityChangedEventHandler VisibilityChanged;

而現在 Xamarin.Forms app 生命週期方法：

//Xamarin.Forms.Application lifecycle methods:
protected virtual void OnResume();
protected virtual void OnSleep();
protected virtual void OnStart();

只需觀察列表就可以輕鬆告訴你，Xamarin.Forms 跨平臺應用程式生命週期視角大大簡化了。它為你提供了關於你的應用程式處於什麼狀態的一般線索，但在大多數生產情況下，你將必須構建一些與平臺相關的邏輯。