Question

我在Clojure中使用了grundid的NFC库，但是当我尝试编写时，我遇到了一个令人讨厌的错误。在Java中它起作用：

public class TextWriter implements NdefOperationsListener {

@Override
public void onNdefOperations(NdefOperations ndefOperations) {
    System.out.println("Formated: " + ndefOperations.isFormatted() + " Writable: " + ndefOperations.isWritable());
    if (ndefOperations.isWritable()) {
        System.out.println("Writing NDEF data...");
        TextRecord record = new TextRecord("It works!");
        if (ndefOperations.isFormatted())
            ndefOperations.writeNdefMessage(record);
        else
            ndefOperations.format(record);
        System.out.println("Done");
    }
    else
        System.out.println("Tag not writable");
}

它开始使用此代码：

protected void launchDemo(NfcTagListener... listeners) throws IOException {
    NfcAdapter nfcAdapter = new NfcAdapter(TerminalUtils.getAvailableTerminal(), TerminalMode.INITIATOR, this);
    for (NfcTagListener tagListener : listeners)
        nfcAdapter.registerTagListener(tagListener);
    nfcAdapter.startListening();
    System.out.println("Waiting for tags, press ENTER to exit");
    System.in.read();
}

此代码由以下内容启动：

test.launchDemo(new MfClassicNfcTagListener(new TextWriter()));

无论如何，这都有效。

clojure代码：

(defn ndef-writer []
  (proxy [NdefOperationsListener] []
    (onNdefOperations [ndefOperations]
                  (println (str "Formatted: " (.isFormatted ndefOperations) " Writable: " (.isWritable ndefOperations)))
                  (if (.isWritable ndefOperations)
                    (do
                      (println "Writing NDEF data...")
                      (if (.isFormatted ndefOperations)
                        (.writeNdefMessage ndefOperations test-record)
                        (.format ndefOperations test-record)))
                    (println "Tag not writable")))

(defn write-demo []
  (doto @nfc-adapter (.registerTagListener (new MfClassicNfcTagListener    (ndef-writer))))
  (.startListening @nfc-adapter)
  (println "Waiting for tag..."))

(defn write-nfc-card []
   (try
     (write-demo)
   (catch Exception e (str "caught exception: " (.getMessage e)))))

但是当我运行clojure代码时，我收到了这个错误：

java.lang.ClassCastException: Cannot cast org.nfctools.ndef.wkt.records.TextRecord to [Lorg.nfctools.ndef.Record;

at java.lang.Class.cast(Class.java:3258)

at clojure.lang.Reflector.boxArg(Reflector.java:427)

at clojure.lang.Reflector.boxArgs(Reflector.java:460)

at clojure.lang.Reflector.invokeMatchingMethod(Reflector.java:58)

at clojure.lang.Reflector.invokeInstanceMethod(Reflector.java:28)

at duva_desktop.nfc.write$ndef_writer$fn__6403.invoke(write.clj:48)

at duva_desktop.nfc.write.proxy$java.lang.Object$NdefOperationsListener$62ccf694.onNdefOperations(Unknown Source)

at org.nfctools.mf.classic.MfClassicNfcTagListener.handleTag(MfClassicNfcTagListener.java:54)

at org.nfctools.NfcAdapter.onTag(NfcAdapter.java:81)

at org.nfctools.spi.acs.InitiatorTerminalTagScanner.handleCard(InitiatorTerminalTagScanner.java:89)

at org.nfctools.spi.acs.InitiatorTerminalTagScanner.run(InitiatorTerminalTagScanner.java:55)

at java.lang.Thread.run(Thread.java:745)

我基本上编码了相同的代码，但后来在Clojure中它失败了，因为它无法将TextRecord转换为Record（TextRecord扩展了WellKnownRecord，它扩展了Record）（它不应该尝试转换吗？）

(instance? Record test-record) true

提前致谢！

P.S。

(def test-record
  (new TextRecord "it workedddd"))

Answer 1

我不熟悉NFC，但问题在错误消息中得到了很好的解释：

java.lang.ClassCastException: Cannot cast org.nfctools.ndef.wkt.records.TextRecord to [Lorg.nfctools.ndef.Record;

注意类名前面的L. L表示它是一个数组。你调用的方法主要是采用varargs，在java中意味着它是数组。因此，您的代码适用于java，但不适用于clojure。在clojure中你必须显式传递数组，你可以这样做：

(into-array [test-record])

使用nfc-tools的clojure classcastexception bug

1 个答案: