When to add javascript interface to listen post messages

[littlesalt]

In order to solve this problem(#309 ), I am using this branches ,but I can't also synchronize your master.
I highly recommend merging the branch into the master branch!

[sakinaboriwala]

@littlesalt

I have commented on 309 . Please check and help me out if possible.

[OPY-bbt]

I solved this problem in iOS and Android, I hope it's helpful。#457

[ashbin]

@OPY-bbt Can you merge please.

[rinlv]

I solved this problem with dynamic channel name for Android and iOS #523. Hope it's helpful

[PhanPirang]

@rinlv I clone your repo, after i click on Display Datetime button, I got "Uncaught ReferenceError: Print is not defined", what's the problem with Channel?

[rinlv]

@PhanPirang Print is the channel, which Flutter will declare to listen to post messages from JS. Never mind about it.