要实现安卓无需用户交互发送Gmail的功能，可以使用Android的Gmail API。下面是一个使用Java语言的示例代码：

首先，在AndroidManifest.xml文件中添加以下权限和服务声明：

接下来，创建一个名为GmailSender的类，用于发送Gmail消息：

import android.accounts.Account;
import android.accounts.AccountManager;
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;

import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.googleapis.extensions.android.gms.auth.GoogleAccountCredential;
import com.google.api.client.googleapis.json.GoogleJsonResponseException;
import com.google.api.client.googleapis.services.AbstractGoogleClientRequest;
import com.google.api.client.googleapis.services.CommonGoogleClientRequestInitializer;
import com.google.api.client.googleapis.services.json.AbstractGoogleJsonClient;
import com.google.api.client.googleapis.services.json.AbstractGoogleJsonClient.Builder;
import com.google.api.client.http.HttpRequestInitializer;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.services.gmail.Gmail;
import com.google.api.services.gmail.GmailScopes;
import com.google.api.services.gmail.model.Message;
import com.google.api.services.gmail.model.MessagePart;
import com.google.api.services.gmail.model.ModifyMessageRequest;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Collections;
import java.util.List;

public class GmailSender {

    private static final String TAG = "GmailSender";
    private static final String APPLICATION_NAME = "Your Application Name";
    private static final String SCOPES = GmailScopes.GMAIL_SEND;
    private static final String USER_ID = "me";

    private Context context;
    private Gmail gmailService;

    public GmailSender(Context context) {
        this.context = context;
        this.gmailService = buildGmailService();
    }

    private Gmail buildGmailService() {
        GoogleAccountCredential credential = GoogleAccountCredential.usingOAuth2(
                context, Collections.singleton(SCOPES))
                .setSelectedAccount(getGoogleAccount());

        HttpRequestInitializer requestInitializer = new CommonGoogleClientRequestInitializer() {
            @Override
            protected void initialize(AbstractGoogleClientRequest request) throws IOException {
                super.initialize(request);
                request.setDisableGZipContent(true);
            }
        };

        Builder builder = new Builder(
                AndroidHttp.newCompatibleTransport(),
                new JacksonFactory(),
                credential)
                .setHttpRequestInitializer(requestInitializer)
                .setApplicationName(APPLICATION_NAME);

        return builder.build();
    }

    private String getGoogleAccount() {
        Account[] accounts = AccountManager.get(context).getAccountsByType("com.google");
        if (accounts.length > 0) {
            return accounts[0].name;
        }
        return null;
    }

    public void sendEmail(String recipient, String subject, String body) {
        new SendEmailTask(recipient, subject, body).execute();
    }

    private class SendEmailTask extends AsyncTask {

        private String recipient;
        private String subject;
        private String body;

        public SendEmailTask(String recipient, String subject, String body) {
            this.recipient = recipient;
            this.subject = subject;
            this.body = body;
        }

        @Override
        protected Void doInBackground(Void... params) {
            try {
                Message message = createMessageWithEmail(createEmail(recipient, subject, body));
                gmailService.users().messages().send(USER_ID, message).execute();
                Log.d(TAG, "Email sent successfully");
            } catch (IOException e) {
                Log.e(TAG, "Failed to send email", e);
            }
            return null;
        }

        private Message createMessageWithEmail(Message emailContent) throws IOException {
            ByteArrayOutputStream buffer = new ByteArrayOutputStream();
            emailContent.encode(buffer);
            byte[] bytes = buffer.toByteArray();
            String encodedEmail = android.util.Base64.encodeToString(bytes, android.util.Base64.URL_SAFE);
            Message message = new Message();
            message.setRaw(encodedEmail);
            return message;
        }

        private Message create