Playground.Forms.Droid can't resume after being hidden by back key

[flyingxu]

Steps to reproduce

1. Clone the latest code, develop branch

2. Set Playground.Forms.Droid as the startup project, compile it. (in my case, I have to change the compiler SDK to 7.1 and the target SDK same as compiling SDK because the original setting of SDK is not installed on my computer).

3. Run Playground.Forms.Droid on real device or simulator. After a loading page, the "Root page" is displayed.

4. Press "Back" button of the device or the simulator to hide the app. Then Tap the app again to resume it.

Expected behavior

"Playground.Forms.Droid" should display the Root page.

Actual behavior

There is a white blank page displaying. At the phase, the Back key is not working (I can't exit or hide the app by pressing back button)

Configuration

Version: 5.4 (should be the latest develop branch)

Platform:

• iOS
• Android
• WPF
• UWP
• MacOS
• tvOS
• Xamarin.Forms

Xamarin.Forms version is 2.4.0.282, the original version which is not updated during the test.

[flyingxu]

The issue still exists after I upgraded "Xamarin.Forms" to version="2.4.0.38779"