是否可以通过意图在活动之间传递URL？

Question

我正在开发一个Android应用程序，它读取NFC标签，检索NDEF消息，然后将其传递给WebView activity以显示那个URL网站。我正在检查Logcat，并且正在读取URL，但我认为URL没有被传递，因为我得到以下错误：

Attempt to cast generated internal exception:
    java.lang.ClassCastException: android.os.Parcelable[] cannot be cast to java.lang.String

这是主要活动：

class MainActivity : AppCompatActivity() {
    // NFC adapter for checking NFC state in the device
    private var nfcAdapter: NfcAdapter? = null

    // Pending intent for NFC intent foreground dispatch.
    // Used to read all NDEF tags while the app is running in the foreground.
    private var nfcPendingIntent: PendingIntent? = null
    // Optional: filter NDEF tags this app receives through the pending intent.
    //private var nfcIntentFilters: Array<IntentFilter>? = null

    private val KEY_LOG_TEXT = "logText"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Restore saved text if available
        if (savedInstanceState != null) {
            dahcor.text = savedInstanceState.getCharSequence(KEY_LOG_TEXT)
        }

        // Check if NFC is supported and enabled
        nfcAdapter = NfcAdapter.getDefaultAdapter(this)
        Log.i("NFC supported", (nfcAdapter != null).toString())
        Log.i("NFC enabled", (nfcAdapter?.isEnabled).toString())


        // Read all tags when app is running and in the foreground
        // Create a generic PendingIntent that will be deliver to this activity. The NFC stack
        // will fill in the intent with the details of the discovered tag before delivering to
        // this activity.
        nfcPendingIntent = PendingIntent.getActivity(this, 0,
                Intent(this, javaClass).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0)

        // Optional: Setup an intent filter from code for a specific NDEF intent
        // Use this code if you are only interested in a specific intent and don't want to
        // interfere with other NFC tags.
        // In this example, the code is commented out so that we get all NDEF messages,
        // in order to analyze different NDEF-formatted NFC tag contents.
        //val ndef = IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED)
        //ndef.addCategory(Intent.CATEGORY_DEFAULT)
        //ndef.addDataScheme("https")
        //ndef.addDataAuthority("*.andreasjakl.com", null)
        //ndef.addDataPath("/", PatternMatcher.PATTERN_PREFIX)
        // More information: https://stackoverflow.com/questions/30642465/nfc-tag-is-not-discovered-for-action-ndef-discovered-action-even-if-it-contains
        //nfcIntentFilters = arrayOf(ndef)

        if (intent != null) {
            // Check if the app was started via an NDEF intent
            Log.i("Found intent in onCreate", intent.action.toString())
            processIntent(intent)
        }

        // Make sure the text view is scrolled down so that the latest messages are visible
    }

    override fun onResume() {
        super.onResume()
        // Get all NDEF discovered intents
        // Makes sure the app gets all discovered NDEF messages as long as it's in the foreground.
        nfcAdapter?.enableForegroundDispatch(this, nfcPendingIntent, null, null);
        // Alternative: only get specific HTTP NDEF intent
        //nfcAdapter?.enableForegroundDispatch(this, nfcPendingIntent, nfcIntentFilters, null);
    }

    override fun onPause() {
        super.onPause()
        // Disable foreground dispatch, as this activity is no longer in the foreground
        nfcAdapter?.disableForegroundDispatch(this);
    }

    override fun onNewIntent(intent: Intent?) {
        super.onNewIntent(intent)
        Log.i("Found intent in onNewIntent", intent?.action.toString())
        // If we got an intent while the app is running, also check if it's a new NDEF message
        // that was discovered
        if (intent != null) processIntent(intent)
    }

    /**
     * Check if the Intent has the action "ACTION_NDEF_DISCOVERED". If yes, handle it
     * accordingly and parse the NDEF messages.
     * @param checkIntent the intent to parse and handle if it's the right type
     */
    private fun processIntent(checkIntent: Intent) {
        // Check if intent has the action of a discovered NFC tag
        // with NDEF formatted contents
        if (checkIntent.action == NfcAdapter.ACTION_NDEF_DISCOVERED) {
            Log.i("New NDEF intent", checkIntent.toString())

            // Retrieve the raw NDEF message from the tag
            val rawMessages = checkIntent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES)
            if (rawMessages != null) {
                Log.i("Raw messages", rawMessages.size.toString())
            }

            // Complete variant: parse NDEF messages
            if (rawMessages != null) {
                val messages = arrayOfNulls<NdefMessage?>(rawMessages.size)// Array<NdefMessage>(rawMessages.size, {})
                for (i in rawMessages.indices) {
                    messages[i] = rawMessages[i] as NdefMessage
                    val intent = Intent(this, Webview::class.java)
                    intent.putExtra("Url", rawMessages)
                    startActivity(intent)
                }
                // Process the messages array.
                processNdefMessages(messages)
            }

            // Simple variant: assume we have 1x URI record
            //if (rawMessages != null && rawMessages.isNotEmpty()) {
            //    val ndefMsg = rawMessages[0] as NdefMessage
            //    if (ndefMsg.records != null && ndefMsg.records.isNotEmpty()) {
            //        val ndefRecord = ndefMsg.records[0]
            //        if (ndefRecord.toUri() != null) {
            //            logMessage("URI detected", ndefRecord.toUri().toString())
            //        } else {
            //            // Other NFC Tags
            //            logMessage("Payload", ndefRecord.payload.contentToString())
            //        }
            //    }
            //}

        }
    }

这是Webview activity，它应该获取URL并加载它：

class Webview : AppCompatActivity() {

    private lateinit var webview: Webview1
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_webview)

        val myWebView: WebView = findViewById(R.id.webview)
        val url = intent.getStringExtra("Url").toString()
        if (url != null) {
            Log.i("Url", url)
        }
        myWebView.webViewClient = object : WebViewClient () {
            override fun shouldOverrideUrlLoading(view: WebView?, url: String?): Boolean {

                if (url != null) {
                    view?.loadUrl(url)
                }
                return true
            }
        }
        myWebView.loadUrl(url)
        myWebView.settings.javaScriptEnabled=true
        myWebView.settings.allowContentAccess=true
        myWebView.settings.domStorageEnabled=true
        myWebView.settings.useWideViewPort=true
    }
}

我想获取从标记接收到的URL到

myWebView.loadUrl()

稍后将加载网站。谢谢你的帮助。

Answer 1

与：

val messages = arrayOfNulls<NdefMessage?>(rawMessages.size);

您将得到一个ndefmessage数组。每个“ndefmessage”都扩展了Parcelable，因此扩展了Parcelable的任何对象都可以很容易地在一个Bundle中put（）。在这种特殊情况下，您有“ndefmessage[]”，表示“parcelable[]”，因此您必须执行以下操作：

intent.putParcelableArray("urls", rawMessages);

和activity：

Parcelable[] parcelables = b.getParcelableArray("urls");
  //just to be sure only NdefMessages can be used
final ArrayList<NdefMessage> ndefMessages = new ArrayList<>();
if (parcelables != null) {
  for (Parcelable parcelable : parcelables) {
      if (!(parcelable instanceof NdefMessage)) continue;
      ndefMessages.add(parcelable);
  }
}
  //HERE: "ndefMessages" contains all NdefMessages received

我从来没有使用过Kotlin但它应该可以工作（当我将Java代码复制/粘贴到KT文件时，AndroidStudio问我是否要将其转换为Kotlin...）：

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val parcelables = savedInstanceState?.getParcelableArray("urls")
    val ndefMessages = ArrayList<NdefMessage>();
    if (parcelables != null) {
        for (parcelable in parcelables) {
            if (parcelable !is NdefMessage) continue
            ndefMessages.add(parcelable)
        }
    }
}

Answer 2

您正在有意传递可Parcelable对象

intent.putExtra("Url", rawMessages)

从rawmessages获取字符串url，然后您将在Webview activity中收到该url