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在 Web 应用中使用 Google Picker API 功能

本文档介绍了如何使用 Google Picker API 功能，例如启用多选、隐藏导航窗格，以及选择具有应用当前 OAuth 2.0 令牌的用户账号。

前提条件

在此示例中，您需要指定以下几项：

如需查找客户端 ID 和 API 密钥，请执行以下操作：
1. 在 Google Cloud 控制台中，依次前往“菜单”图标 > API 和服务 > 凭据。
  
  转到“凭据”页面
如需查找应用 ID，请执行以下操作：
1. 在 Google Cloud 控制台中，依次前往“菜单”图标 > IAM 和管理 > 设置。
  
  转到“设置”
2. 使用项目编号作为应用 ID。

同一 Google Cloud 云项目必须同时包含客户端 ID 和应用 ID，因为它们用于授权访问用户的文件。

在 HTML 文档中创建图片选择器应用

以下代码示例展示了如何使用图片选择器或上传页面，用户可以从 Web 应用中的按钮打开该选择器或上传页面。

创建一个标准 HTML 文档来托管 Google 选择器：

<!DOCTYPE html>
<html>
<head>
  <title>Google Picker API Quickstart</title>
  <meta charset="utf-8" />
</head>
<body>
<p>Google Picker API Quickstart</p>

<!--Add buttons to initiate auth sequence and sign out.-->
<button id="authorize_button" onclick="handleAuthClick()">Authorize</button>
<button id="signout_button" onclick="handleSignoutClick()">Sign Out</button>

<pre id="content" style="white-space: pre-wrap;"></pre>

使用 JavaScript 调用 Google Picker API：

<script type="text/javascript">
  /* exported gapiLoaded */
  /* exported gisLoaded */
  /* exported handleAuthClick */
  /* exported handleSignoutClick */

  // Authorization scopes required by the API; multiple scopes can be
  // included, separated by spaces.
  const SCOPES = 'https://www.googleapis.com/auth/drive.metadata.readonly';

  // Replace with your client ID and API key from https://console.cloud.google.com/.
  const CLIENT_ID = 'CLIENT_ID';
  const API_KEY = 'API_KEY';

  // Replace with your project number from https://console.cloud.google.com/.
  const APP_ID = 'APP_ID';

  let tokenClient;
  let accessToken = null;
  let pickerInited = false;
  let gisInited = false;

  document.getElementById('authorize_button').style.visibility = 'hidden';
  document.getElementById('signout_button').style.visibility = 'hidden';

  /**
   * Callback after api.js is loaded.
   */
  function gapiLoaded() {
    gapi.load('client:picker', initializePicker);
  }

  /**
   * Callback after the API client is loaded. Loads the
   * discovery doc to initialize the API.
   */
  async function initializePicker() {
    await gapi.client.load('https://www.googleapis.com/discovery/v1/apis/drive/v3/rest');
    pickerInited = true;
    maybeEnableButtons();
  }

  /**
   * Callback after Google Identity Services are loaded.
   */
  function gisLoaded() {
    tokenClient = google.accounts.oauth2.initTokenClient({
      client_id: CLIENT_ID,
      scope: SCOPES,
      callback: '', // defined later
    });
    gisInited = true;
    maybeEnableButtons();
  }

  /**
   * Enables user interaction after all libraries are loaded.
   */
  function maybeEnableButtons() {
    if (pickerInited && gisInited) {
      document.getElementById('authorize_button').style.visibility = 'visible';
    }
  }

  /**
   *  Sign in the user upon button click.
   */
  function handleAuthClick() {
    tokenClient.callback = async (response) => {
      if (response.error !== undefined) {
        throw (response);
      }
      accessToken = response.access_token;
      document.getElementById('signout_button').style.visibility = 'visible';
      document.getElementById('authorize_button').innerText = 'Refresh';
      await createPicker();
    };

    if (accessToken === null) {
      // Prompt the user to select a Google Account and ask for consent to share their data
      // when establishing a new session.
      tokenClient.requestAccessToken({prompt: 'consent'});
    } else {
      // Skip display of account chooser and consent dialog for an existing session.
      tokenClient.requestAccessToken({prompt: ''});
    }
  }

  /**
   *  Sign out the user upon button click.
   */
  function handleSignoutClick() {
    if (accessToken) {
      google.accounts.oauth2.revoke(accessToken);
      accessToken = null;
      document.getElementById('content').innerText = '';
      document.getElementById('authorize_button').innerText = 'Authorize';
      document.getElementById('signout_button').style.visibility = 'hidden';
    }
  }

  /**
   *  Create and render a Google Picker object for searching images.
   */
  function createPicker() {
    const view = new google.picker.View(google.picker.ViewId.DOCS);
    view.setMimeTypes('image/png,image/jpeg,image/jpg');
    const picker = new google.picker.PickerBuilder()
        .enableFeature(google.picker.Feature.NAV_HIDDEN)
        .enableFeature(google.picker.Feature.MULTISELECT_ENABLED)
        .setDeveloperKey(API_KEY)
        .setAppId(APP_ID)
        .setOAuthToken(accessToken)
        .addView(view)
        .addView(new google.picker.DocsUploadView())
        .setCallback(pickerCallback)
        .build();
    picker.setVisible(true);
  }

  /**
   * Displays the file details of the user's selection.
   * @param {object} data - Contains the user selection from the Google Picker.
   */
  async function pickerCallback(data) {
    if (data.action === google.picker.Action.PICKED) {
      let text = `Google Picker response: \n${JSON.stringify(data, null, 2)}\n`;
      const selectedDoc = data[google.picker.Response.DOCUMENTS][0];
      const fileId = selectedDoc[google.picker.Document.ID];
      console.log(fileId);
      const res = await gapi.client.drive.files.get({
        'fileId': fileId,
        'fields': '*',
      });
      text += `Drive API response for first document: \n${JSON.stringify(res.result, null, 2)}\n`;
      window.document.getElementById('content').innerText = text;
    }
  }
</script>
<script async defer src="https://apis.google.com/js/api.js" onload="gapiLoaded()"></script>
<script async defer src="https://accounts.google.com/gsi/client" onload="gisLoaded()"></script>

替换以下内容：

CLIENT_ID：您在为 Web 应用授权 OAuth 2.0 凭证时创建的客户端 ID。
API_KEY：您创建的 API 密钥凭据。
APP_ID：Google Cloud 项目中的项目编号。

借助 setOAuthToken 函数，应用可以使用当前的身份验证令牌来确定 Google 选择器使用哪个 Google 账号来显示文件。如果用户登录了多个 Google 账号，Google 选择器可以显示相应授权账号的文件。

关闭 HTML 文档：

</body>
</html>

从 Google 选择器获取文件 ID 后，应用便可按照 files 资源的 get 方法中所述，提取文件元数据并下载文件内容。

创建图片选择器对象

以下代码示例展示了构建、渲染和处理 Google Picker API 以创建图片选择器的核心逻辑。