以下是一个使用Java代码在Android设备上读取云文件的示例：

1. 首先，确保你的Android项目中添加了所需的依赖库。在你的项目的build.gradle文件中添加以下依赖项：

implementation 'com.google.api-client:google-api-client-android:1.23.0'
implementation 'com.google.apis:google-api-services-drive:v3-rev305-1.23.0'

2. 创建一个新的类来处理与Google Drive API的通信。命名为GoogleDriveService.java：

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

import com.google.android.gms.auth.GoogleAuthUtil;
import com.google.android.gms.auth.GoogleAuthUtil;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.Scope;
import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.googleapis.extensions.android.gms.auth.GoogleAccountCredential;
import com.google.api.client.googleapis.extensions.android.gms.auth.GoogleCredential;
import com.google.api.client.http.FileContent;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.http.InputStreamContent;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.services.drive.Drive;
import com.google.api.services.drive.DriveScopes;
import com.google.api.services.drive.model.File;
import com.google.api.services.drive.model.FileList;

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

public class GoogleDriveService {

    private static final String TAG = "GoogleDriveService";
    private static final String APPLICATION_NAME = "Your Application Name";
    private static final JsonFactory JSON_FACTORY = JacksonFactory.getDefaultInstance();

    private Drive driveService;

    public GoogleDriveService(Context context, String accountName) {
        GoogleAccountCredential credential = GoogleAccountCredential.usingOAuth2(
                context, Collections.singleton(DriveScopes.DRIVE_FILE));
        credential.setSelectedAccountName(accountName);

        HttpTransport httpTransport = new NetHttpTransport();
        driveService = new Drive.Builder(
                httpTransport, JSON_FACTORY, credential)
                .setApplicationName(APPLICATION_NAME)
                .build();
    }

    public void readFile(String fileId) {
        new ReadFileAsyncTask().execute(fileId);
    }

    private class ReadFileAsyncTask extends AsyncTask {

        @Override
        protected Void doInBackground(String... params) {
            String fileId = params[0];
            try {
                File file = driveService.files().get(fileId).execute();
                String fileContent = file.getName();

                Log.d(TAG, "File Content: " + fileContent);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }
    }
}

3. 在你的Activity类中，调用GoogleDriveService类的readFile方法来读取云文件。例如，命名为MainActivity.java：

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    private GoogleDriveService googleDriveService;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        googleDriveService = new GoogleDriveService(this, "[email protected]");
        googleDriveService.readFile("your_file_id");
    }
}

请注意，上述示例仅演示了如何使用Google Drive API读取云文件。你需要替换 [email protected]和your_file_id 为你自己的账号和文件ID。

此外，你还需要在AndroidManifest.xml文件中添加以下权限：

你还需要在Google Cloud Console中创建一个新的项目，并启用Google Drive API，并获取到对应的客户端ID和密钥。

以上是使用Android Java代码读取云文件的基本解决方案。你可以根据需要进行进一步的修改和优化。