wait for channelCallback

[paolosanchi]

In android I want to launch my app by scanning the nfc tag, so I followed what's specified in the doc's section "Launching your Android Application when Scanning a Tag"
The issue is that if I scan the tag with the app turned off it crashes at launch time.
It seems that the method execute(), which sets channelCallback is called after sendEvent()

So channelCallback is null and there is nothing that catches the exception

phonegap-nfc/src/android/src/com/chariotsolutions/nfc/plugin/NfcPlugin.java

Lines 730 to 745 in d325b86

	// Send the event data through a channel so the JavaScript side can fire the event
	private void sendEvent(String type, JSONObject tag) {
	try {
	JSONObject event = new JSONObject();
	event.put("type", type); // TAG_DEFAULT, NDEF, NDEF_MIME, NDEF_FORMATABLE
	event.put("tag", tag); // JSON representing the NFC tag and NDEF messages
	PluginResult result = new PluginResult(PluginResult.Status.OK, event);
	result.setKeepCallback(true);
	channelCallback.sendPluginResult(result);
	} catch (JSONException e) {
	Log.e(TAG, "Error sending NFC event through the channel", e);
	}
	}

the stack of sendEvent() is this one:
onNewIntent() -> parseMessage() -> cordova.getThreadPool().execute(()=>) -> fireNdefEvent() -> sendEvent()

So what I done is to wait until channelCallback got set.

Warning!
What I did is to add a potential infinite loop, which could potentially block the thread, but it seems that sendEvent() is executed on a thread took from the threadPool (cordova.getThreadPool().execute(()=>)) so it should be fine.

In the end, it does the job done.

Maybe the problem comes from my environment:

• ionic (angular)
• capacitorJs
• phonegap codrova plugin

[paolosanchi]

I've added another commit to avoid the infinite loop, that's a waste of cpu, so I've added a list of sleeping thread that has to be awaken then the channel is ready