使用Gmail API从收件箱中获取邮件

Question

我在我的Android应用程序中集成了Gmail API，并且我使用了API的入门页面提供的代码进行连接，我已经成功执行了该代码，现在我想从收件箱中获取消息，因为我使用了以下代码为此我得到了

  

403 forbidden error with message Insufficient permission

我没有弄错我在做什么？请帮帮我。

 private class GetMessages extends AsyncTask<Void, Void, List<Message>> {
    private com.google.api.services.gmail.Gmail mService = null;
    private Exception mLastError = null;

    GetMessages(GoogleAccountCredential credential) {
        HttpTransport transport = AndroidHttp.newCompatibleTransport();
        JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
        mService = new com.google.api.services.gmail.Gmail.Builder(
                transport, jsonFactory, credential)
                .setApplicationName("Gmail API Android Quickstart")
                .build();
    }

    /**
     * Background task to call Gmail API.
     * @param params no parameters needed for this task.
     */
    @Override
    protected List<Message> doInBackground(Void... params) {
        try {
            return getDataFromApi();
        } catch (Exception e) {
            mLastError = e;
            cancel(true);
            return null;
        }
    }

    /**
     * Fetch a list of Gmail labels attached to the specified account.
     * @return List of Strings labels.
     * @throws IOException
     */
    private List<Message> getDataFromApi() throws IOException {
        // Get the labels in the user's account.
        String user = "me";
        List<Message> messages = new LinkedList<>();
        ListMessagesResponse listMessageResponse =null;
        Gmail.Users.Messages.List request = mService.users().messages().list(user)
                .setLabelIds(Arrays.asList("INBOX"))
                .setMaxResults(Long.parseLong("10"))
                ;

        do {
            listMessageResponse = request.execute();
            messages.addAll(listMessageResponse.getMessages());
            request.setPageToken(listMessageResponse.getNextPageToken());

        } while (request.getPageToken() != null && request.getPageToken().length() > 0);
        return messages;
    }


    @Override
    protected void onPreExecute() {
        mOutputText.setText("");
        mProgress.show();
    }

    @Override
    protected void onPostExecute(List<Message> output) {
        mProgress.hide();
        if (output == null || output.size() == 0) {
            mOutputText.setText("No results returned.");
        } else {
            mOutputText.setText(TextUtils.join("\n", output));
        }
    }

    @Override
    protected void onCancelled() {
        mProgress.hide();
        if (mLastError != null) {
            if (mLastError instanceof GooglePlayServicesAvailabilityIOException) {
                showGooglePlayServicesAvailabilityErrorDialog(
                        ((GooglePlayServicesAvailabilityIOException) mLastError)
                                .getConnectionStatusCode());
            } else if (mLastError instanceof UserRecoverableAuthIOException) {
                startActivityForResult(
                        ((UserRecoverableAuthIOException) mLastError).getIntent(),
                        MainActivity.REQUEST_AUTHORIZATION);
            } else {
                mOutputText.setText("The following error occurred:\n"
                        + mLastError.getMessage());
            }
        } else {
            mOutputText.setText("Request cancelled.");
        }
    }
}