How can I make sure Android Beam doesn't start a new instance of my 'singleTop' activity?

Question

First, the use case : 2 phones have my app opened on the same screen. I want one user to be able to share the screen content (data) with the other one without necessarily opening a new instance of the activity when beaming using NFC. (both Android devices are running Ice Cream Sandwich)

So I have a singleTop activity declared like this in the manifest.

<activity android:name=".activity.MyActivity" android:configChanges="orientation|keyboardHidden" android:launchMode="singleTop">
  <intent-filter android:label="@string/activityLabel">
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.DEFAULT" />
    <data android:mimeType="a.b.c/x.y.z" />
  </intent-filter>
  <intent-filter>
    <action android:name="android.nfc.action.NDEF_DISCOVERED"/>
    <category android:name="android.intent.category.DEFAULT"/>
    <data android:mimeType="application/x.y.z"/>
  </intent-filter>
</activity>

When a VIEW action is fired and the activity is already on top, the onNewIntent() method is called in the same instance if the activity.

When a NDEF_DISCOVERED action is fired and the activity is already on top, the onCreate() method is called in a new instance of the activity.

score 4 · Answer 1 · edited Dec 08 '13 at 14:09

4

You describe the case that the app is already open and the proper Activity is in the foreground. In that case, you can make use of the foreground-dispatching of NFC intents by calling NfcAdapter.enableForegroundDispatch() in your Activity's onResume() (and disableForegroudDispatch() in onPause()). This will force all NFC Intents to be delivered to your Activity (via onNewIntent()).

edited Dec 08 '13 at 14:09

ozbek

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answered Feb 20 '12 at 20:21

NFC guy

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This looks like the way to go but I don't have a 2nd NFC-capable device to test it out now. Doc: http://developer.android.com/guide/topics/nfc/advanced-nfc.html#foreground-dispatch – mmathieum Feb 22 '12 at 00:23
3

Using an NFC tag with an NDEF message would give virtually the same result as receiving data via Android Beam. Perhaps you can try that. – NFC guy Feb 23 '12 at 00:23

score 0 · Answer 2 · answered May 10 '12 at 13:00

0

You should use: android:launchMode="singleInstance" Works for me.

answered May 10 '12 at 13:00

Klaasvaak

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launchMode "singleInstance" is only for home screen replacements. In my case "singleTask" worked perfectly. – Androbin Aug 03 '16 at 14:26

score 0 · Answer 3 · answered Feb 19 '12 at 20:02

I don't have an answer for you. But I have a workaround: have the NDEF_DISCOVERED start a new activity. Make that activity invisible (Theme.NoBackground) and in the onCreate, make it start the MyActivity with singleTop and finish immediately. MyActivity should now appear with onNewIntent.

score 0 · Answer 4 · answered Feb 23 '12 at 02:48

0

Have you looked at the Android Beam sample:

http://developer.android.com/resources/samples/AndroidBeamDemo/index.html

It implements this behavior that you want (minus VIEW intent filtering). I'm not sure if that intent will affect the NDEF_DISCOVERED one, but it would be interesting to maybe modify the Android Beam sample to see if you can cause the same behavior as your app.

answered Feb 23 '12 at 02:48

robertly

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I looked at the Android Beam sample (started by this actually) and it doesn't implement the foreground dispatching that I'm trying to achieve here. – mmathieum Feb 23 '12 at 05:21

How can I make sure Android Beam doesn't start a new instance of my 'singleTop' activity?

4 Answers4