Bug when re-opening the android app with the app icon.

[tralves]

Steps to reproduce:

1. If you open an app
2. Close it with the Android back physical button
3. Open it again through the app icon

Expected

The app opens normaly

Result

You get the error:

This error happened with both the Groceries Vue app and the ui-tests app.

[blackss2]

I have same problem and you can fix that problem with this boiler plate way.

NativeScript/NativeScript#4960

finally i found root of this problem.
what you see is only occurred at Vue cuz it reuse page if not destroyed using below code.
this is first clue.

    if (!prevVnode) {
      // initial render
      vm.$el = vm.__patch__(
        vm.$el, vnode, hydrating, false /* removeOnly */,
        vm.$options._parentElm,
        vm.$options._refElm
      );
    } else {
      // updates
      vm.$el = vm.__patch__(prevVnode, vnode);
    }

other example application doesn't make this problem but application context is not saved.
this is second clue.

if you [start application using auto sync -> home button -> start using app button -> back button] will make second activity.
this is last clue.

my conclusion is that [debug(auto syncing) app] and [run by app icon] doesn't use same activity.
if you add some condtion to if(!prevVnode) -> if(!prevVnode || true), your problem is disappeared.
it means [app icon activity try to getting Page's view] that owned by [debug activity Page's view].
it make [view already has a parent] error.
so it is not nativescript-vue's problem.
it just development side problem that not occurred at released application.

[rigor789]

Just for reference here is the Activity lifecycle diagram, I think we need to implement android specific behavior (hook into the lifecycle) to handle resumed activities: https://developer.android.com/guide/components/activities/activity-lifecycle.html#alc

[seohangyu]

@blackss2
I tried with the release. But still bugs happen.

[blackss2]

Try this
#78