Bug 8572 - On try make a Ndef ReadOnly throws exeption
Summary: On try make a Ndef ReadOnly throws exeption
Status: RESOLVED INVALID
Alias: None
Product: Android
Classification: Xamarin
Component: Mono runtime / AOT Compiler ()
Version: 4.2.x
Hardware: PC Windows
: --- normal
Target Milestone: ---
Assignee: Bugzilla
URL:
Depends on:
Blocks:
 
Reported: 2012-11-23 11:54 UTC by Marco A. (Gh0stman)
Modified: 2012-11-29 12:28 UTC (History)
2 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED INVALID

Description Marco A. (Gh0stman) 2012-11-23 11:54:07 UTC
CODE:
Ndef ndef = Ndef.Get(tag);
                if (ndef != null)
                {
                    ndef.Connect();

                    if (!ndef.IsWritable)
                    {
                        //displayMessage("Read-only tag.");
                        return false;
                    }

                    // work out how much space we need for the data
                    int size = message.ToByteArray().Length;
                    if (ndef.MaxSize < size)
                    {
                        //displayMessage("Tag doesn't have enough free space.");
                        return false;
                    }

                    ndef.WriteNdefMessage(message);
                    try
                    {
                        bool vReadyOnly = ndef.MakeReadOnly();
                    }
                    catch (Exception ex)
                    {
                        string ret = ex.Message;
                    }
                    RunOnUiThread(() => Toast.MakeText(this, "Crédito gravado com sucesso!", ToastLength.Short));
                    //displayMessage("Tag written successfully.");
                    return true;
                }
EXCEPTION:
{Java.IO.IOException: Exception of type 'Java.IO.IOException' was thrown.
  at Android.Runtime.JNIEnv.CallBooleanMethod (IntPtr jobject, IntPtr jmethod) [0x00023] in /Users/builder/data/lanes/monodroid-mac-monodroid-4.2.7-branch/0e9eea34/source/monodroid/src/Mono.Android/src/Runtime/JNIEnv.g.cs:156 
  at Android.Nfc.Tech.Ndef.MakeReadOnly () [0x0002d] in /Users/builder/data/lanes/monodroid-mac-monodroid-4.2.7-branch/0e9eea34/source/monodroid/src/Mono.Android/platforms/android-15/src/generated/Android.Nfc.Tech.Ndef.cs:155 
  at BusTravelCard.Activities.FinishCard.writeTag (Android.Nfc.Tag tag) [0x00405] in C:\Trabalho\Sistemas\Bus\MonoDroid\BusTravelCard\BusTravelCard\Activities\FinishCard.cs:202 
  --- End of managed exception stack trace ---
java.io.IOException
	at android.nfc.tech.Ndef.makeReadOnly(Ndef.java:375)
	at bustravelcard.activities.FinishCard.n_onNewIntent(Native Method)
	at bustravelcard.activities.FinishCard.onNewIntent(FinishCard.java:55)
	at android.app.Instrumentation.callActivityOnNewIntent(Instrumentation.java:1127)
	at android.app.ActivityThread.deliverNewIntents(ActivityThread.java:2056)
	at android.app.ActivityThread.performNewIntents(ActivityThread.java:2069)
	at android.app.ActivityThread.handleNewIntent(ActivityThread.java:2078)
	at android.app.ActivityThread.access$1400(ActivityThread.java:128)
	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1208)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loop(Looper.java:137)
	at android.app.ActivityThread.main(ActivityThread.java:4517)
	at java.lang.reflect.Method.invokeNative(Native Method)
	at java.lang.reflect.Method.invoke(Method.java:511)
	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
	at dalvik.system.NativeStart.main(Native Method)
}
Comment 1 Marco A. (Gh0stman) 2012-11-23 12:18:09 UTC
Today I write a NDEF message on the card/tag with no problems.
But now I want to protect the NDEF message from be overwriten by someone else (other app).
Looking on the docs I see two options FormatReadOnly(message); or WriteNdefMessage(message); MakeReadOnly();

On this test I was trying to write/protect and re-write with the new variant of the text.

The app is a credit card for a store. User fill with credits (get some bonus and stuff for use the card) and when he/she use the credit the new value is put in the card. The tag is a AES encripted text.

If you guys have any ideas I would love to hear.
Comment 2 Jonathan Pryor 2012-11-29 12:28:54 UTC
This does not appear to be a bug in Mono for Android.

> On try make a Ndef ReadOnly throws exeption

The IOException is a documented error condition:

http://developer.android.com/reference/android/nfc/tech/Ndef.html#makeReadOnly()
http://androidapi.xamarin.com/?link=M%3aAndroid.Nfc.Tech.Ndef.MakeReadOnly()

One interesting note from the documentation:

> It must not be called from the main application thread.

Based on the stack trace, it looks like you're calling it from the main application thread (based on the android.app.ActivityThread.main() entry). If that's the case, Don't Do That™.