bitcoin core – Can an unsynchronized node create a valid transaction?

Node A is holding a chain which is not in sync with the rest of the
nodes and node A decides to post a transaction.

If node A created transaction from valid unspent UTXO (which is valid on longest chain), the transaction will be valid. You don’t have to be even a node to send this valid, signed transaction, you can mail it to the node C which will include it into mempool.

The miners will pick up this transaction and add them to a block in
their own chain which is different than Node A’s chain.

As long as your node has communication with these miners, yes (there are different scenarios of “unsyncing”, I assume hardforks as well, but I guessed you meant orphan blocks mostly, or lack of recent blocks?).

So now when Node A looks at the network, will it just ignore its own
inconsistent chain and pick the miners chain?

No. If you are looking at top of chain A which isn’t in sync with the longest chain, where miners should add the transaction, your node won’t see it. The rest of the network on the longest chain will observe it though.

Will the transaction made by node A even show up in the blockchain?

Yes, in the longest chain.

Material Design – Android App – How to indicate that unsynchronized data exists?

I have an Android application where users can create different types of content in different screens of the app. All content is synchronized with the server in a background thread. Usually, this happens immediately when new data is created. However, if the device is offline, unsynchronized content may persist for a long time.

To alert the user (so he is not surprised when comparing app content and server content via the web interface), I thought about displaying an indicator somewhere in the app.

I'm not sure how / where to show such an indicator. I can not display the indicator in the action bar because it is used in many screens for different purposes.

Ideas so far

  • Display the indicator as a kind of stack on the navigation bar icon ("Hamburger" icon), but that would be pretty small.
  • Use a notification, but since the indicator disappears by itself once the synchronization is complete, this seems to be a kind of misuse of the notification idea.
  • Display a colored line at the top or bottom of the action bar. However, this is not self-explanatory.