Android Beam - payload transfer from both devices

问题:

Ok, I watched the Google I/O from 2011 presentation on NFC on peer to peer.

The demo was done on Gingerbread and using the application Sticky Notes found

Now in this demo, both device the onNewIntent() was called at the same time so both devices are trying to share information to one another.

On ICS and above, you have Android Beam..

With Android Beam, you have to touch to trigger the onNewIntent() event that will send the NDef message across.

Now the problem with this is that now to trigger the onNewIntent() on both devices, both user on each device has to "Touch To Beam" at the same time.

Is there a way that when you Touch To Beam on one device, both can have the onNewIntent() to be called?

I am trying to develop an app that will exchange data to each other but for it to work in a nice friendly fashion I need the devices to share the data at the same time once the Touch To Beam has been initiated on one device. I do hope this is possible.

Edit: It looks like this might not be possible to do :(

回答1:

As far as I can tell, the feature you want is not available over NFC itself. The touch-to-beam/SNEP/NPP transfer is one direction only on Android. The user that clicks his screen will push an NDEF message to the other phone.

What I believe they've done in the video is set up a bluetooth connection with the NDEF message to make the transfer (as you saw in the stickynotes demo). Unfortunately there is no nice API for this.

However, the EasyNFC project promises to be able to allow you to create a bluetooth connection and socket between two phones/applications. Check it out here

I had a try and didn't really like the Touch-to-Beam UI that was still required in the set up of the bluetooth connection. It also didnt really suit my needs, as I wanted to transfer phone to computer and didn't really want to implement NFC P2P and a bluetooth connection.

回答2:

Did you try this:
Use the Touch to Beam on phone-1 to "PUSH" the data, while on the other (phone-2), use the NDEF_DISCOVERED/TECH_DISCOVERED intent to trigger/start the data capture/reception. I vaguely remember one of the above intents were triggered when a PUSH is done. Although, every transmission requires a "Touch" to start the beaming.

回答3:

When you think in general, Android should not allow the NFC data transfer in both direction at the same time. Lets think of a scenario where I want to send a thing to my friend with NFC. What is actively open on my friend's phone is not important. I should send this thing even the same app is not open on the receiver side. There may be another app in my friends phone that tries to send another thing to me. When we touch our phones, Android Beam (TM) appears and he data is sent from the phone that is touched.

In you case I think you should disable Android Beam (TM) by setting setNdefPushMessage(null) and do sending both ways using the old way.

回答4:

https://developer.android.com/preview/api-overview.html

I think it will be available in L!!!

NFC enhancements

Your app can invoke the Android Beam on the user’s device to share data by calling android.nfc.NfcAdapter.invokeBeam(). This avoids the need for the user to manually tap the device against another NFC-capable device to complete the data transfer.