无法将信息添加到 Cloud Firestore

以下代码的目标是从 Android 设备 (api 24) 将数据保存到 Cloud Firestore 中

public class MainActivity extends AppCompatActivity {

public static final String NUM_KEY="num";
public static final String SMS_KEY="sms";
private static final String TAG = "MainActivity";
private DocumentReference mDocRef = FirebaseFirestore.getInstance().document("android/websms");

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

public void saveSMS(View view){
    EditText num = (EditText) findViewById(R.id.num);
    EditText sms = (EditText) findViewById(R.id.msg);
    String quotenum = num.getText().toString();
    String quotesms =  sms.getText().toString();
    Button button = (Button) findViewById(R.id.button);
    Map<String,Object> dataToSave = new HashMap<String, Object>();

    dataToSave.put(NUM_KEY,quotenum);
    dataToSave.put(SMS_KEY,quotesms);
        mDocRef.set(dataToSave).addOnSuccessListener(new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void aVoid) {
                Log.d(TAG, "Document has been saved");
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Log.w(TAG,"Document was not saved",e);
            }
        });

}

我正在 YouTube 上关注一些 Firestore 教程，它似乎有点过时了，因为当我在 Android 设备上运行它时，我在控制台上收到以下错误

04-17 02:09:50.718 2600-2712/com.example.joao.websms1 E/art：Android 版本 >= 6.0 上不存在 String#value 字段

预先感谢任何愿意提供帮助的人。

¿你尝试过使用方法push吗？

mDocRef.push(dataToSave).addOnSuccessListener(new OnSuccessListener<Void>() {
        @Override
        public void onSuccess(Void aVoid) {
            Log.d(TAG, "Document has been saved");
        }
    }).addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            Log.w(TAG,"Document was not saved",e);
        }
    });