Xamarin.Forms how do I access a public function from another CS file?

问题

So I'm new to XF and I'm wondering about AppState/Activity life cycle on Android. The code directly below this is in a file called test.xaml.cs.

How the sound works is you can say something like startSound.Play() or startSound.Stop() to start or stop sound in the app. I have noticed a bug that doesn't stop sound when the rest of the app resets via the back button (even though it's held in memory?)

public Test()
    {
        startSound = CrossSimpleAudioPlayer.CreateSimpleAudioPlayer();
        startSound.Load(Path.Combine($"Audio", "startBeep.wav"));

        stopSound = CrossSimpleAudioPlayer.CreateSimpleAudioPlayer();
        stopSound.Load(Path.Combine($"Audio", "stopBeep.wav"));

        winSound = CrossSimpleAudioPlayer.CreateSimpleAudioPlayer();
        winSound.Load(Path.Combine($"Audio", "winBeep.wav"));

        endSound = CrossSimpleAudioPlayer.CreateSimpleAudioPlayer();
        endSound.Load(Path.Combine($"Audio", "endBeep.wav"));

        addSound = CrossSimpleAudioPlayer.CreateSimpleAudioPlayer();
        addSound.Load(Path.Combine($"Audio", "addBeep.wav"));
    }

What I would like to do is in the app.xaml.cs file to go into protected override void OnSleep() and write startSound.stop(); so that the sound stops whenever the app sleeps. However I do not know how to access the public function of Test in test.xaml.cs.

This is the code line for app.xaml.cs

protected override void OnSleep()
    {
        Debug.WriteLine("OnSleep");
        // Handle when your app sleeps
    }

I've used the debug to make sure that the app state changes so I know the OnSleep() works properly.

回答1:

You can use MessagingCenter to accomplish that.

Xamarin.Forms MessagingCenter enables view models and other components to communicate with without having to know anything about each other besides a simple Message contract.

Just send a message in the OnSleep of your App and subscribe to the message on your Test:

In your OnSleep:

MessagingCenter.Send<App>(this, "OnSleep");

In your Test:

MessagingCenter.Subscribe<App>(this, "OnSleep", (sender) => {
    startSound.stop(); 
});

HIH

来源：https://stackoverflow.com/questions/53522477/xamarin-forms-how-do-i-access-a-public-function-from-another-cs-file

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