Chrome for Android で NFC デバイスを操作する

if ('NDEFReader' in window) { /* Scan and write NFC tags */ } 

const ndef = new NDEFReader(); ndef.scan().then(() => {   console.log("Scan started successfully.");   ndef.onreadingerror = () => {     console.log("Cannot read data from the NFC tag. Try another one?");   };   ndef.onreading = event => {     console.log("NDEF message read.");   }; }).catch(error => {   console.log(`Error! Scan failed to start: ${error}.`); }); 

ndef.onreading = event => {   const message = event.message;   for (const record of message.records) {     console.log("Record type:  " + record.recordType);     console.log("MIME type:    " + record.mediaType);     console.log("Record id:    " + record.id);     switch (record.recordType) {       case "text":         // TODO: Read text record with record data, lang, and encoding.         break;       case "url":         // TODO: Read URL record with record data.         break;       default:         // TODO: Handle other records with record data.     }   } }; 

const ndef = new NDEFReader(); ndef.write(   "Hello World" ).then(() => {   console.log("Message written."); }).catch(error => {   console.log(`Write failed :-( try again: ${error}.`); }); 

const ndef = new NDEFReader(); ndef.write({   records: [{ recordType: "url", data: "https://w3c.github.io/web-nfc/" }] }).then(() => {   console.log("Message written."); }).catch(error => {   console.log(`Write failed :-( try again: ${error}.`); }); 

const ndef = new NDEFReader(); ndef.write({ records: [     { recordType: "url", data: "https://w3c.github.io/web-nfc/" },     { recordType: "url", data: "https://web.dev/nfc/" } ]}).then(() => {   console.log("Message written."); }).catch(error => {   console.log(`Write failed :-( try again: ${error}.`); }); 

const ndef = new NDEFReader(); ndef.write("Writing data on an empty NFC tag is fun!", { overwrite: false }) .then(() => {   console.log("Message written."); }).catch(error => {   console.log(`Write failed :-( try again: ${error}.`); }); 

const ndef = new NDEFReader(); ndef.makeReadOnly() .then(() => {   console.log("NFC tag has been made permanently read-only."); }).catch(error => {   console.log(`Operation failed: ${error}`); }); 

const ndef = new NDEFReader(); try {   await ndef.write("Hello world");   console.log("Message written.");   await ndef.makeReadOnly();   console.log("NFC tag has been made permanently read-only after writing to it."); } catch (error) {   console.log(`Operation failed: ${error}`); } 

if ("NDEFReader" in window && "makeReadOnly" in NDEFReader.prototype) {   // makeReadOnly() is supported. } 

  document.querySelector("#scanButton").onclick = async () => {     const ndef = new NDEFReader();     // Prompt user to allow website to interact with NFC devices.     await ndef.scan();     ndef.onreading = event => {       // TODO: Handle incoming NDEF messages.     };   }; 

document.onvisibilitychange = event => {   if (document.hidden) {     // All NFC operations are automatically suspended when document is hidden.   } else {     // All NFC operations are resumed, if needed.   } }; 

const ndef = new NDEFReader();  async function startScanning() {   await ndef.scan();   ndef.onreading = event => {     /* handle NDEF messages */   }; }  const nfcPermissionStatus = await navigator.permissions.query({ name: "nfc" }); if (nfcPermissionStatus.state === "granted") {   // NFC access was previously granted, so we can start NFC scanning now.   startScanning(); } else {   // Show a "scan" button.   document.querySelector("#scanButton").style.display = "block";   document.querySelector("#scanButton").onclick = event => {     // Prompt user to allow UA to send and receive info when they tap NFC devices.     startScanning();   }; } 

const abortController = new AbortController(); abortController.signal.onabort = event => {   // All NFC operations have been aborted. };  const ndef = new NDEFReader(); await ndef.scan({ signal: abortController.signal });  await ndef.write("Hello world", { signal: abortController.signal }); await ndef.makeReadOnly({ signal: abortController.signal });  document.querySelector("#abortButton").onclick = event => {   abortController.abort(); }; 

// Waiting for user to tap NFC tag to write to it... const ndef = new NDEFReader(); await ndef.write("Hello world"); // Success! Message has been written.  // Now scanning for 3 seconds... const abortController = new AbortController(); await ndef.scan({ signal: abortController.signal }); const message = await new Promise((resolve) => {   ndef.onreading = (event) => resolve(event.message); }); // Success! Message has been read.  await new Promise((r) => setTimeout(r, 3000)); abortController.abort(); // Scanning is now stopped. 

function readTextRecord(record) {   console.assert(record.recordType === "text");   const textDecoder = new TextDecoder(record.encoding);   console.log(`Text: ${textDecoder.decode(record.data)} (${record.lang})`); } 

const ndef = new NDEFReader(); await ndef.write("Hello World"); 

function a2utf16(string) {   let result = new Uint16Array(string.length);   for (let i = 0; i < string.length; i++) {     result[i] = string.codePointAt(i);   }   return result; }  const textRecord = {   recordType: "text",   lang: "fr",   encoding: "utf-16",   data: a2utf16("Bonjour, François !") };  const ndef = new NDEFReader(); await ndef.write({ records: [textRecord] }); 

function readUrlRecord(record) {   console.assert(record.recordType === "url");   const textDecoder = new TextDecoder();   console.log(`URL: ${textDecoder.decode(record.data)}`); } 

const urlRecord = {   recordType: "url",   data:"https://w3c.github.io/web-nfc/" };  const ndef = new NDEFReader(); await ndef.write({ records: [urlRecord] }); 

function readMimeRecord(record) {   console.assert(record.recordType === "mime");   if (record.mediaType === "application/json") {     const textDecoder = new TextDecoder();     console.log(`JSON: ${JSON.parse(decoder.decode(record.data))}`);   }   else if (record.mediaType.startsWith('image/')) {     const blob = new Blob([record.data], { type: record.mediaType });     const img = new Image();     img.src = URL.createObjectURL(blob);     document.body.appendChild(img);   }   else {     // TODO: Handle other MIME types.   } } 

const encoder = new TextEncoder(); const data = {   firstname: "François",   lastname: "Beaufort" }; const jsonRecord = {   recordType: "mime",   mediaType: "application/json",   data: encoder.encode(JSON.stringify(data)) };  const imageRecord = {   recordType: "mime",   mediaType: "image/png",   data: await (await fetch("icon1.png")).arrayBuffer() };  const ndef = new NDEFReader(); await ndef.write({ records: [jsonRecord, imageRecord] }); 

function readAbsoluteUrlRecord(record) {   console.assert(record.recordType === "absolute-url");   const textDecoder = new TextDecoder();   console.log(`Absolute URL: ${textDecoder.decode(record.data)}`); } 

const absoluteUrlRecord = {   recordType: "absolute-url",   data:"https://w3c.github.io/web-nfc/" };  const ndef = new NDEFReader(); await ndef.write({ records: [absoluteUrlRecord] }); 

function readSmartPosterRecord(smartPosterRecord) {   console.assert(record.recordType === "smart-poster");   let action, text, url;    for (const record of smartPosterRecord.toRecords()) {     if (record.recordType == "text") {       const decoder = new TextDecoder(record.encoding);       text = decoder.decode(record.data);     } else if (record.recordType == "url") {       const decoder = new TextDecoder();       url = decoder.decode(record.data);     } else if (record.recordType == ":act") {       action = record.data.getUint8(0);     } else {       // TODO: Handle other type of records such as `:t`, `:s`.     }   }    switch (action) {     case 0:       // Do the action       break;     case 1:       // Save for later       break;     case 2:       // Open for editing       break;   } } 

const encoder = new TextEncoder(); const smartPosterRecord = {   recordType: "smart-poster",   data: {     records: [       {         recordType: "url", // URL record for smart poster content         data: "https://my.org/content/19911"       },       {         recordType: "text", // title record for smart poster content         data: "Funny dance"       },       {         recordType: ":t", // type record, a local type to smart poster         data: encoder.encode("image/gif") // MIME type of smart poster content       },       {         recordType: ":s", // size record, a local type to smart poster         data: new Uint32Array([4096]) // byte size of smart poster content       },       {         recordType: ":act", // action record, a local type to smart poster         // do the action, in this case open in the browser         data: new Uint8Array([0])       },       {         recordType: "mime", // icon record, a MIME type record         mediaType: "image/png",         data: await (await fetch("icon1.png")).arrayBuffer()       },       {         recordType: "mime", // another icon record         mediaType: "image/jpg",         data: await (await fetch("icon2.jpg")).arrayBuffer()       }     ]   } };  const ndef = new NDEFReader(); await ndef.write({ records: [smartPosterRecord] }); 

function readExternalTypeRecord(externalTypeRecord) {   for (const record of externalTypeRecord.toRecords()) {     if (record.recordType == "text") {       const decoder = new TextDecoder(record.encoding);       console.log(`Text: ${textDecoder.decode(record.data)} (${record.lang})`);     } else if (record.recordType == "url") {       const decoder = new TextDecoder();       console.log(`URL: ${decoder.decode(record.data)}`);     } else {       // TODO: Handle other type of records.     }   } } 

const externalTypeRecord = {   recordType: "example.game:a",   data: {     records: [       {         recordType: "url",         data: "https://example.game/42"       },       {         recordType: "text",         data: "Game context given here"       },       {         recordType: "mime",         mediaType: "image/png",         data: await (await fetch("image.png")).arrayBuffer()       }     ]   } };  const ndef = new NDEFReader(); ndef.write({ records: [externalTypeRecord] }); 

const emptyRecord = {   recordType: "empty" };  const ndef = new NDEFReader(); await ndef.write({ records: [emptyRecord] }); 

const encoder = new TextEncoder(); const aarRecord = {   recordType: "android.com:pkg",   data: encoder.encode("com.example.myapp") };  const ndef = new NDEFReader(); await ndef.write({ records: [aarRecord] });