android - 有没有办法使用 Kotlin（不是 Java）将网页下载到本地存储？
问题描述
对于任何想将此问题标记为“重复”的人，请记住，我要求的是 KOTLIN 解决方案，而不是 8 年前的 Java 解决方案。谢谢你。
所以我有这个应用程序，它在 NFC 标签中获取 URL，我希望它下载该网页并将其保存在本地存储中，稍后将在 Webview 中加载。我已经拥有获取 NDEF 消息并将其处理为字符串的功能。我遵循了一些 Java 教程并使用 J2K 转换了文件，但似乎没有一个工作，我相信我做错了什么，但我似乎无法在这里或谷歌上找到解决方案。我曾尝试将 URL 记录到控制台，但我想我也做错了。
我将把 MainActivity 类留给你：
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)
val instance = Download()
Log.i("Url download", instance.toString())
// 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)
Download()
Download()
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)
val url = rawMessages
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
}
// 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())
// }
// }
//}
}
}
/**
* Parse the NDEF message contents and print these to the on-screen log.
*/
private fun processNdefMessages(ndefMessages: Array<NdefMessage?>) {
// Go through all NDEF messages found on the NFC tag
for (curMsg in ndefMessages) {
if (curMsg != null) {
// Print generic information about the NDEF message
Log.i("Message", curMsg.toString())
// The NDEF message usually contains 1+ records - print the number of recoreds
Log.i("Records", curMsg.records.size.toString())
// Loop through all the records contained in the message
for (curRecord in curMsg.records) {
if (curRecord.toUri() != null) {
// URI NDEF Tag
val url = curRecord.toUri().toString()
val intent = Intent(this, Webview::class.java)
intent.putExtra("Url", url)
startActivity(intent)
Log.i("- URI", curRecord.toUri().toString())
} else {
// Other NDEF Tags - simply print the payload
Log.i("- Contents", curRecord.payload!!.contentToString())
}
}
}
}
}
fun Download(args: Array<String>) {
val fileName = intent.getStringExtra("Url")
val url = fileName.toString().trim()
if(url.toString()!=null && url.toString().trim()!=""){
val fileOutputStream: FileOutputStream
try {
fileOutputStream = openFileOutput(url, Context.MODE_PRIVATE)
} catch (e: FileNotFoundException){
e.printStackTrace()
}catch (e: NumberFormatException){
e.printStackTrace()
}catch (e: IOException){
e.printStackTrace()
}catch (e: Exception){
e.printStackTrace()
}
Toast.makeText(applicationContext,"data save", Toast.LENGTH_LONG).show()
}
fun download(urlString: String?) {
// Create URL object
val url = URL(urlString)
fun writeFileOnInternalStorage(mcoContext: Context, sFileName: String?, sBody: String?) {
val dir = File(mcoContext.filesDir, "Files")
if (!dir.exists()) {
dir.mkdir()
// Enter filename in which you want to download
BufferedReader(InputStreamReader(url.openStream())).use { reader ->
BufferedWriter(FileWriter("${url}.html")).use { writer ->
// read each line from stream till end
var line: String?
while (reader.readLine().also { line = it } != null) {
writer.write(line)
}
println("Page downloaded.")
}
}
}
// Exceptions
try {
val gpxfile = File(dir, sFileName)
val writer = FileWriter(gpxfile)
writer.append(sBody)
writer.flush()
writer.close()
} catch (e: Exception) {
e.printStackTrace()
}
}}
}
}