Implement canMakeReadonly().

The method is needed since makeReadOnly() only works on T1T/T2T. Also removed
makeLowlevelReadonly(), since NFC forum does not allow setting the CC and the lock
bits separately.

Change-Id: I8e6d7c065b1f017ef07d878c41df05e1a8193f5a

core/java/android/nfc/technology/Ndef.java

@@ -224,7 +224,22 @@ public final class Ndef extends BasicTagTechnology {
     }
 
     /**
-     * Set the CC field to indicate this tag is read-only
+     * Indicates whether a tag can be made read-only with
+     * {@link #makeReadonly()}
+     */
+    public boolean canMakeReadonly() {
+        if (mNdefType == NFC_FORUM_TYPE_1 || mNdefType == NFC_FORUM_TYPE_2) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /**
+     * Sets the CC field to indicate this tag is read-only
+     * and permanently sets the lock bits to prevent any further NDEF
+     * modifications.
+     * This is a one-way process and can not be reverted!
      * @throws IOException
      */
     public boolean makeReadonly() throws IOException {
@@ -249,17 +264,6 @@ public final class Ndef extends BasicTagTechnology {
         }
     }
 
-    /**
-     * Attempt to use tag specific technology to really make
-     * the tag read-only
-     * For NFC Forum Type 1 and 2 only.
-     */
-    public void makeLowLevelReadonly() {
-        checkConnected();
-
-        throw new UnsupportedOperationException();
-    }
-
     @Override
     public byte[] transceive(byte[] data) {
         checkConnected();