提升應用程式的安全性

val intent = Intent(Intent.ACTION_SEND) val possibleActivitiesList: List<ResolveInfo> =         packageManager.queryIntentActivities(intent, PackageManager.MATCH_ALL)  // Verify that an activity in at least two apps on the user's device // can handle the intent. Otherwise, start the intent only if an app // on the user's device can handle the intent. if (possibleActivitiesList.size > 1) {      // Create intent to show chooser.     // Title is something similar to "Share this photo with."      val chooser = resources.getString(R.string.chooser_title).let { title ->         Intent.createChooser(intent, title)     }     startActivity(chooser) } else if (intent.resolveActivity(packageManager) != null) {     startActivity(intent) }

Intent intent = new Intent(Intent.ACTION_SEND); List<ResolveInfo> possibleActivitiesList = getPackageManager()         .queryIntentActivities(intent, PackageManager.MATCH_ALL);  // Verify that an activity in at least two apps on the user's device // can handle the intent. Otherwise, start the intent only if an app // on the user's device can handle the intent. if (possibleActivitiesList.size() > 1) {      // Create intent to show chooser.     // Title is something similar to "Share this photo with."      String title = getResources().getString(R.string.chooser_title);     Intent chooser = Intent.createChooser(intent, title);     startActivity(chooser); } else if (intent.resolveActivity(getPackageManager()) != null) {     startActivity(intent); }

val url = URL("https://www.google.com") val urlConnection = url.openConnection() as HttpsURLConnection urlConnection.connect() urlConnection.inputStream.use {     ... }

URL url = new URL("https://www.google.com"); HttpsURLConnection urlConnection = (HttpsURLConnection) url.openConnection(); urlConnection.connect(); InputStream in = urlConnection.getInputStream();

val myWebView: WebView = findViewById(R.id.webview)  // channel[0] and channel[1] represent the two ports. // They are already entangled with each other and have been started. val channel: Array<out WebMessagePort> = myWebView.createWebMessageChannel()  // Create handler for channel[0] to receive messages. channel[0].setWebMessageCallback(object : WebMessagePort.WebMessageCallback() {      override fun onMessage(port: WebMessagePort, message: WebMessage) {         Log.d(TAG, "On port $port, received this message: $message")     } })  // Send a message from channel[1] to channel[0]. channel[1].postMessage(WebMessage("My secure message"))

WebView myWebView = (WebView) findViewById(R.id.webview);  // channel[0] and channel[1] represent the two ports. // They are already entangled with each other and have been started. WebMessagePort[] channel = myWebView.createWebMessageChannel();  // Create handler for channel[0] to receive messages. channel[0].setWebMessageCallback(new WebMessagePort.WebMessageCallback() {     @Override     public void onMessage(WebMessagePort port, WebMessage message) {          Log.d(TAG, "On port " + port + ", received this message: " + message);     } });  // Send a message from channel[1] to channel[0]. channel[1].postMessage(new WebMessage("My secure message"));

// Delegates the responsibility of creating the contact to a contacts app, // which has already been granted the appropriate WRITE_CONTACTS permission. Intent(Intent.ACTION_INSERT).apply {     type = ContactsContract.Contacts.CONTENT_TYPE }.also { intent ->     // Make sure that the user has a contacts app installed on their device.     intent.resolveActivity(packageManager)?.run {         startActivity(intent)     } }

// Delegates the responsibility of creating the contact to a contacts app, // which has already been granted the appropriate WRITE_CONTACTS permission. Intent insertContactIntent = new Intent(Intent.ACTION_INSERT); insertContactIntent.setType(ContactsContract.Contacts.CONTENT_TYPE);  // Make sure that the user has a contacts app installed on their device. if (insertContactIntent.resolveActivity(getPackageManager()) != null) {     startActivity(insertContactIntent); }

// Create an Intent to launch a PDF viewer for a file owned by this app. Intent(Intent.ACTION_VIEW).apply {     data = Uri.parse("content://com.example/personal-info.pdf")      // This flag gives the started app read access to the file.     addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION) }.also { intent ->     // Make sure that the user has a PDF viewer app installed on their device.     intent.resolveActivity(packageManager)?.run {         startActivity(intent)     } }

// Create an Intent to launch a PDF viewer for a file owned by this app. Intent viewPdfIntent = new Intent(Intent.ACTION_VIEW); viewPdfIntent.setData(Uri.parse("content://com.example/personal-info.pdf"));  // This flag gives the started app read access to the file. viewPdfIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);  // Make sure that the user has a PDF viewer app installed on their device. if (viewPdfIntent.resolveActivity(getPackageManager()) != null) {     startActivity(viewPdfIntent); }

// Creates a file with this name, or replaces an existing file // that has the same name. Note that the file name cannot contain // path separators. val FILE_NAME = "sensitive_info.txt" val fileContents = "This is some top-secret information!" File(filesDir, FILE_NAME).bufferedWriter().use { writer ->     writer.write(fileContents) }

// Creates a file with this name, or replaces an existing file // that has the same name. Note that the file name cannot contain // path separators. final String FILE_NAME = "sensitive_info.txt"; String fileContents = "This is some top-secret information!"; try (BufferedWriter writer =              new BufferedWriter(new FileWriter(new File(getFilesDir(), FILE_NAME)))) {     writer.write(fileContents); } catch (IOException e) {     // Handle exception. }

val FILE_NAME = "sensitive_info.txt" val contents = File(filesDir, FILE_NAME).bufferedReader().useLines { lines ->     lines.fold("") { working, line ->         "$working\n$line"     } }

final String FILE_NAME = "sensitive_info.txt"; StringBuffer stringBuffer = new StringBuffer(); try (BufferedReader reader =              new BufferedReader(new FileReader(new File(getFilesDir(), FILE_NAME)))) {      String line = reader.readLine();     while (line != null) {         stringBuffer.append(line).append('\n');         line = reader.readLine();     } } catch (IOException e) {     // Handle exception. }

val hash = calculateHash(stream) // Store "expectedHash" in a secure location. if (hash == expectedHash) {     // Work with the content. }  // Calculating the hash code can take quite a bit of time, so it shouldn't // be done on the main thread. suspend fun calculateHash(stream: InputStream): String {     return withContext(Dispatchers.IO) {         val digest = MessageDigest.getInstance("SHA-512")         val digestStream = DigestInputStream(stream, digest)         while (digestStream.read() != -1) {             // The DigestInputStream does the work; nothing for us to do.         }         digest.digest().joinToString(":") { "%02x".format(it) }     } }

Executor threadPoolExecutor = Executors.newFixedThreadPool(4); private interface HashCallback {     void onHashCalculated(@Nullable String hash); }  boolean hashRunning = calculateHash(inputStream, threadPoolExecutor, hash -> {     if (Objects.equals(hash, expectedHash)) {         // Work with the content.     } });  if (!hashRunning) {     // There was an error setting up the hash function. }  private boolean calculateHash(@NonNull InputStream stream,                               @NonNull Executor executor,                               @NonNull HashCallback hashCallback) {     final MessageDigest digest;     try {         digest = MessageDigest.getInstance("SHA-512");     } catch (NoSuchAlgorithmException nsa) {         return false;     }      // Calculating the hash code can take quite a bit of time, so it shouldn't     // be done on the main thread.     executor.execute(() -> {         String hash;         try (DigestInputStream digestStream =                 new DigestInputStream(stream, digest)) {             while (digestStream.read() != -1) {                 // The DigestInputStream does the work; nothing for us to do.             }             StringBuilder builder = new StringBuilder();             for (byte aByte : digest.digest()) {                 builder.append(String.format("%02x", aByte)).append(':');             }             hash = builder.substring(0, builder.length() - 1);         } catch (IOException e) {             hash = null;         }          final String calculatedHash = hash;         runOnUiThread(() -> hashCallback.onHashCalculated(calculatedHash));     });     return true; }

val cacheFile = File(myDownloadedFileUri).let { fileToCache ->     File(cacheDir.path, fileToCache.name) }

File cacheDir = getCacheDir(); File fileToCache = new File(myDownloadedFileUri); String fileToCacheName = fileToCache.getName(); File cacheFile = new File(cacheDir.getPath(), fileToCacheName);