Android 访问用户时出现NullPointerException'；使用谷歌日历API的日历列表

我想使用GoogleCalendarAPI来提取日历、事件等。我有android中AccountManager类的身份验证令牌。因此，通过这种方式，如果用户使用其google帐户登录手机，那么我可以轻松检索与他相关的身份验证令牌。 之后，我将执行以下操作：

 public Calendar useCalendarAPI(final String accessToken) {

 try{

      HttpTransport transport = new NetHttpTransport();
      AccessProtectedResource accessProtectedResource = new GoogleAccessProtectedResource(accessToken);
      Calendar.Builder builder = Calendar.builder(transport, new JacksonFactory());
      builder.setApplicationName("My App Name");
      builder.setHttpRequestInitializer(accessProtectedResource);
      JsonHttpRequestInitializer json = new JsonHttpRequestInitializer() {
          public void initialize(JsonHttpRequest request) {
                CalendarRequest calRequest = (CalendarRequest) request;
                calRequest.setKey(Common.API_KEY);
                calRequest.setOauthToken(accessToken);
            }
            };
      builder.setJsonHttpRequestInitializer(json);

      Calendar calendarService= builder.build();
      
      if(calendarService!= null)
      {
          return calendarService;
      }
      else
          return null;
      }catch (Exception e) {
        // TODO: handle exception
          e.getMessage();
    }

在此之后，我收到一个名为“calendarService”的日历对象

这是从Google日历API文档中复制的。 检查此链接
但是我在下面一行得到了null指针异常

CalendarList calendarList = calendarService.calendarList().list().execute();

请提出一些建议

---

谢谢

嘿，我有一个小的工作样本，它也是用你提到的同一个日历文档制作的。如果您可以随代码一起提供堆栈跟踪，也会有所帮助

 public static void main(String[] args) throws IOException {
    HttpTransport httpTransport = new NetHttpTransport();
    JacksonFactory jsonFactory = new JacksonFactory();
    String clientId = "CLIENT ID";
    String clientSecret = "CLIENT SECRET";
    String redirectUrl = "urn:ietf:wg:oauth:2.0:oob";
    String scope = "https://www.googleapis.com/auth/calendar";
    String authorizationUrl = new GoogleAuthorizationRequestUrl(clientId, redirectUrl, scope)
    .build();
    System.out.println("Go to the following link in your browser:");
    System.out.println(authorizationUrl);
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    System.out.println("What is the authorization code?");
    String code = in.readLine();
    AccessTokenResponse response = new GoogleAuthorizationCodeGrant(httpTransport, jsonFactory,
        clientId, clientSecret, code, redirectUrl).execute();
    GoogleAccessProtectedResource accessProtectedResource = new GoogleAccessProtectedResource(
        response.accessToken, httpTransport, jsonFactory, clientId, clientSecret,
        response.refreshToken);

    Calendar calendarService = Calendar.builder(httpTransport, jsonFactory)
        .setApplicationName("YOUR_APPLICATION_NAME")
        .setHttpRequestInitializer(accessProtectedResource)
        .build();
    try     
    {
      com.google.api.services.calendar.model.CalendarList calendarList = calendarService.calendarList().list().execute();

      while (true) {
        for (CalendarListEntry calendarListEntry : calendarList.getItems()) {
          System.out.println(calendarListEntry.getSummary());
        }
        String pageToken = calendarList.getNextPageToken();
        if (pageToken != null && !pageToken.equalsIgnoreCase("")) {
          calendarList = calendarService.calendarList().list().setPageToken(pageToken).execute();

        } else {
          break;
        }
      }

    } catch (Exception e) {
      e.printStackTrace();
    }
  }

---

看起来您需要将

calendarService

作为参数传递给

getCalendarsList（）

函数

我通过Google calendar private API实现了日历集成。谢谢

 public static void main(String[] args) throws IOException {
    HttpTransport httpTransport = new NetHttpTransport();
    JacksonFactory jsonFactory = new JacksonFactory();
    String clientId = "CLIENT ID";
    String clientSecret = "CLIENT SECRET";
    String redirectUrl = "urn:ietf:wg:oauth:2.0:oob";
    String scope = "https://www.googleapis.com/auth/calendar";
    String authorizationUrl = new GoogleAuthorizationRequestUrl(clientId, redirectUrl, scope)
    .build();
    System.out.println("Go to the following link in your browser:");
    System.out.println(authorizationUrl);
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    System.out.println("What is the authorization code?");
    String code = in.readLine();
    AccessTokenResponse response = new GoogleAuthorizationCodeGrant(httpTransport, jsonFactory,
        clientId, clientSecret, code, redirectUrl).execute();
    GoogleAccessProtectedResource accessProtectedResource = new GoogleAccessProtectedResource(
        response.accessToken, httpTransport, jsonFactory, clientId, clientSecret,
        response.refreshToken);

    Calendar calendarService = Calendar.builder(httpTransport, jsonFactory)
        .setApplicationName("YOUR_APPLICATION_NAME")
        .setHttpRequestInitializer(accessProtectedResource)
        .build();
    try     
    {
      com.google.api.services.calendar.model.CalendarList calendarList = calendarService.calendarList().list().execute();

      while (true) {
        for (CalendarListEntry calendarListEntry : calendarList.getItems()) {
          System.out.println(calendarListEntry.getSummary());
        }
        String pageToken = calendarList.getNextPageToken();
        if (pageToken != null && !pageToken.equalsIgnoreCase("")) {
          calendarList = calendarService.calendarList().list().setPageToken(pageToken).execute();

        } else {
          break;
        }
      }

    } catch (Exception e) {
      e.printStackTrace();
    }
  }