XamarinForms AppCompat OnOptionsItemSelected

问题

I have recently updated xamarin forms to 1.5.1-pre1 so that I can use the beautiful AppCompat themes. It works and looks very nice.

I do have one problem, in my old FormsApplicationActivity I used to override the OnOptionsItemSelected method to intercept when the user was clicking on the back arrow icon and do some viewmodel cleanup. Apparently this method is not being called after using the FormsAppCompatActivity. How can I intercept the "soft" back button press (toolbar icon not hard back button) ?

I also tried to override the Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer but i can't seem to override it :(

Does anyone have a clue how I can intercept this?

回答1:

Have a look at the last two lines of the OnCreate() After adding them OnOptionsItemSelected was called as expected).

https://raw.githubusercontent.com/UdaraAlwis/Xamarin-Playground/master/XFNavBarBackBtnClickOverride/XFNavBarBackBtnClickOverride/XFNavBarBackBtnClickOverride.Droid/MainActivity.cs

        Toolbar toolbar = this.FindViewById<Toolbar>(Resource.Id.toolbar);

        SetSupportActionBar(toolbar);

回答2:

You can add the following to your custom renderer. You can either user current activity plugin or cast your context to activity.

var toolbar = CrossCurrentActivity.Current?.Activity?.FindViewById<Toolbar>(Resource.Id.toolbar);

toolbar.NavigationClick += ToolbarNavigationClick;

回答3:

In Xamarin.Forms there's a better way to intercept the NavigationBar back button pressed and the hardware back button pressed, which is creating your own NavigationRenderer and overriding the method OnPopViewAsync:

[assembly: ExportRenderer(typeof(NavigationPage), typeof(CustomNavigationRenderer))]
namespace YourApp.Droid
{
    public class CustomNavigationRenderer : NavigationPageRenderer
    {
        public CustomNavigationRenderer(Context context) : base(context)
        {
        }

        protected override async Task<bool> OnPopViewAsync(Page page, bool animated)
        {
            // Write your code here
        }
    }
}

Hope this helps

来源：https://stackoverflow.com/questions/33078590/xamarinforms-appcompat-onoptionsitemselected