Maps JavaScript API 中的網頁元件 (預先發布版)

網頁元件是熱門的 W3C 標準，能將 HTML、CSS 和 JS 封裝在可重複使用的自訂 HTML 元素中。這些可重複使用的元件種類廣泛，有小型的功能組成元素 (例如顯示星級評等)，也有複雜的商業邏輯。本指南將說明 Maps JavaScript API 所提供的網頁元件。

如要進一步瞭解這項標準，請參閱「網頁元件」一文。

適用對象

本說明文件旨在協助您快速起步，探索如何使用網頁元件開發應用程式。建議需先熟悉 HTML 和 CSS 程式設計概念。

顯示地圖

開始學習網頁元件最簡單的方法，就是查看範例。以下範例顯示聖荷西區域的地圖。

TypeScript

// This example adds a map using web components.
function initMap(): void {
    console.log('Maps JavaScript API loaded.');
}

declare global {
    interface Window {
        initMap: () => void;
    }
}
window.initMap = initMap;
index.ts

JavaScript

// This example adds a map using web components.
function initMap() {
  console.log("Maps JavaScript API loaded.");
}

window.initMap = initMap;
index.js

CSS

/* 
 * Always set the map height explicitly to define the size of the div element
 * that contains the map. 
 */
#map {
  height: 100%;
}

/* 
 * Optional: Makes the sample page fill the window. 
 */
html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

gmp-map {
  height: 400px;
}

style.css

HTML

<html>
  <head>
    <title>Add a Map Web Component</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>

    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script type="module" src="./index.js"></script>
  </head>
  <body>
    <gmp-map
      center="37.4220656,-122.0840897"
      zoom="10"
      map-id="DEMO_MAP_ID"
    ></gmp-map>

    <!-- 
      The `defer` attribute causes the callback to execute after the full HTML
      document has been parsed. For non-blocking uses, avoiding race conditions,
      and consistent behavior across browsers, consider loading using Promises.
      See https://developers.google.com/maps/documentation/javascript/load-maps-js-api
      for more information.
      -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initMap&v=beta"
      defer
    ></script>
  </body>
</html>
index.html

測試範例

在本例中，有幾個地方需要注意：

  1. Maps JavaScript API 是非同步呼叫的。回呼函式會用來判斷載入 API 的時間。
  2. 地圖的呈現方式是以 <gmp-map> 自訂元素來決定。
  3. 定義地圖屬性的方式，是在 <gmp-map> 自訂元素中指定屬性。
  4. 樣式可以透過內嵌的方式套用至自訂元素，或是在獨立 CSS 檔案中宣告。

設定基本地圖的樣式

地圖 ID 是指與特定地圖樣式或地圖項目相關聯的 ID。如要使用自選的雲端設定功能，請將雲端式地圖樣式設定 DEMO_MAP_ID 換成您自己的地圖 ID。如要瞭解如何建立地圖 ID 並設定自訂樣式，請參閱「雲端式地圖樣式設定」一文。

在地圖中加入標記

就像建立內建 HTML 代碼的巢狀結構來塑造複雜的內容階層一樣，您也可以在元素內建立 <gmp-advanced-marker> 的巢狀結構來顯示一或多個地圖標記。

TypeScript

// This example adds a map with markers, using web components.
function initMap(): void {
    console.log('Maps JavaScript API loaded.');
}

declare global {
    interface Window {
        initMap: () => void;
    }
}
window.initMap = initMap;
index.ts

JavaScript

// This example adds a map with markers, using web components.
function initMap() {
  console.log("Maps JavaScript API loaded.");
}

window.initMap = initMap;
index.js

CSS

/* 
 * Always set the map height explicitly to define the size of the div element
 * that contains the map. 
 */
#map {
  height: 100%;
}

/* 
 * Optional: Makes the sample page fill the window. 
 */
html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

gmp-map {
  height: 400px;
}

style.css

HTML

<html>
  <head>
    <title>Add a Map with Markers using Web Components</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>

    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script type="module" src="./index.js"></script>
  </head>
  <body>
    <gmp-map center="43.4142989,-124.2301242" zoom="4" map-id="DEMO_MAP_ID">
      <gmp-advanced-marker
        position="37.4220656,-122.0840897"
        title="Mountain View, CA"
      ></gmp-advanced-marker>
      <gmp-advanced-marker
        position="47.648994,-122.3503845"
        title="Seattle, WA"
      ></gmp-advanced-marker>
    </gmp-map>

    <!-- 
      The `defer` attribute causes the callback to execute after the full HTML
      document has been parsed. For non-blocking uses, avoiding race conditions,
      and consistent behavior across browsers, consider loading using Promises.
      See https://developers.google.com/maps/documentation/javascript/load-maps-js-api
      for more information.
      -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initMap&libraries=marker&v=beta"
      defer
    ></script>
  </body>
</html>
index.html

測試範例

這裡我們在 <gmp-map> 自訂元素內加入了兩個 <gmp-advanced-marker> 元素。title 的文字可為指定元素在游標懸停時額外提供顯示文字，也可當做無障礙標籤。

JavaScript 事件

網頁元件的主要好處是易於使用。只要加入幾行程式碼，就算是對 JavaScript 或進階程式設計瞭解有限的人，還是能順利顯示地圖畫面。導入完成後，您會發現這段程式碼的運作模式，和其他熟悉的 HTML 元素一樣。舉例來說，您可以運用原生瀏覽器事件系統，回應地圖或進階標記動作 (例如按下標記)。

TypeScript

// This example adds a map using web components.
function initMap(): void {
  console.log('Maps JavaScript API loaded.');
  const advancedMarkers = document.querySelectorAll("#marker-click-event-example gmp-advanced-marker");
  for (const advancedMarker of advancedMarkers) {

    customElements.whenDefined(advancedMarker.localName).then(async () => {
      advancedMarker.addEventListener('gmp-click', async () => {

        const infoWindow = new google.maps.InfoWindow({
          //@ts-ignore
          content: advancedMarker.title,
        });
        infoWindow.open({
          //@ts-ignore
          anchor: advancedMarker
        });
      });
    });
  }
}

declare global {
  interface Window {
    initMap: () => void;
  }
}
window.initMap = initMap;
index.ts

JavaScript

// This example adds a map using web components.
function initMap() {
  console.log("Maps JavaScript API loaded.");

  const advancedMarkers = document.querySelectorAll(
    "#marker-click-event-example gmp-advanced-marker",
  );

  for (const advancedMarker of advancedMarkers) {
    customElements.whenDefined(advancedMarker.localName).then(async () => {
      advancedMarker.addEventListener("gmp-click", async () => {
        const infoWindow = new google.maps.InfoWindow({
          //@ts-ignore
          content: advancedMarker.title,
        });

        infoWindow.open({
          //@ts-ignore
          anchor: advancedMarker,
        });
      });
    });
  }
}

window.initMap = initMap;
index.js

CSS

/* 
 * Always set the map height explicitly to define the size of the div element
 * that contains the map. 
 */
#map {
  height: 100%;
}

/* 
 * Optional: Makes the sample page fill the window. 
 */
html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

gmp-map {
  height: 400px;
}

style.css

HTML

<html>
  <head>
    <title>Add a Map Web Component with Events</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>

    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script type="module" src="./index.js"></script>
  </head>
  <body>
    <gmp-map
      id="marker-click-event-example"
      center="43.4142989,-124.2301242"
      zoom="4"
      map-id="DEMO_MAP_ID"
    >
      <gmp-advanced-marker
        position="37.4220656,-122.0840897"
        title="Mountain View, CA"
      ></gmp-advanced-marker>
      <gmp-advanced-marker
        position="47.648994,-122.3503845"
        title="Seattle, WA"
      ></gmp-advanced-marker>
    </gmp-map>

    <!-- 
      The `defer` attribute causes the callback to execute after the full HTML
      document has been parsed. For non-blocking uses, avoiding race conditions,
      and consistent behavior across browsers, consider loading using Promises.
      See https://developers.google.com/maps/documentation/javascript/load-maps-js-api
      for more information.
      -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initMap&libraries=marker&v=beta"
      defer
    ></script>
  </body>
</html>
index.html

測試範例

在本例中，initMap 代表 Maps JavaScript API 完全載入後所需使用的回呼函式。這段程式碼會建立每個標記的事件監聽器，每當有人按下這些標記時，就會顯示資訊視窗。

後續步驟