如何在Android的Firestore中的自动生成的文档ID文档中添加多个子集合？

Question

我想要一个类似image的数据库，我可以在其中为每个创建一次的文档添加多个子集合。例如。输入用户详细信息后，会在文档中创建一个子集合（机构部门），这将进一步在同一文档中创建子集合（建议）。我正在使用不同的Java类来获取各种详细信息。例如：我封闭了两个类，即sports_detail和建议：

package com.example.admin.howdy;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.google.firebase.firestore.FirebaseFirestore;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class sportpage extends AppCompatActivity {

    CheckBox kabaddi,volley,basket,other,cricket,race;
    EditText textView,contactsport;
    Button button3;
    FirebaseFirestore mfirestore;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sportpage);
        kabaddi=(CheckBox)findViewById(R.id.checkBox2);
        volley=(CheckBox)findViewById(R.id.checkBox3);
        basket=(CheckBox)findViewById(R.id.checkBox5);
        race=(CheckBox)findViewById(R.id.checkBox4);
        cricket=(CheckBox)findViewById(R.id.checkBox6);
        other=(CheckBox)findViewById(R.id.checkBox7);
        textView=(EditText) findViewById(R.id.sportcontestant);
        contactsport=(EditText) findViewById(R.id.sportcontact);
        mfirestore = FirebaseFirestore.getInstance();
        button3 = (Button) findViewById(R.id.button);
        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sendsportdetail();
                Intent i=new Intent(sportpage.this,Thanks.class);
                startActivity(i);
            }
        });
    }

    private void sendsportdetail()
    {
        Map<String, String> usmap=new HashMap<>();
        String name=textView.getText().toString().trim();
        String contact=contactsport.getText().toString().trim();
        String text="";
        if (kabaddi.isChecked()){
                text = kabaddi.getText().toString();
               usmap.put("Category", text);
            }
        if (basket.isChecked()){
            text = basket.getText().toString();
            usmap.put("Category", text);
        }
        if (volley.isChecked()){
            text = volley.getText().toString();
            usmap.put("Category", text);
        }
        if (cricket.isChecked()){
            text = cricket.getText().toString();
            usmap.put("Category", text);
        }
        if (race.isChecked()){
            text = race.getText().toString();
            usmap.put("Category", text);
        }
        if (other.isChecked()){
            text = other.getText().toString();
            usmap.put("Category", text);
        }
        if(!kabaddi.isChecked()&&!race.isChecked()&&!cricket.isChecked()&&!other.isChecked()&&!basket.isChecked()&&!volley.isChecked())
            Toast.makeText(getBaseContext(),"Please select an option",Toast.LENGTH_LONG).show();
        usmap.put("Name",name);
        usmap.put("Contact",contact);
        //String str=mfirestore.collection("MYPrince").document().getId();
        //Toast.makeText(getBaseContext(),str,Toast.LENGTH_LONG).show();
        mfirestore.collection("MYPrince").document().collection("Sports_Registration").add(usmap);
    }
}

package com.example.admin.howdy;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.firestore.DocumentReference;
import com.google.firebase.firestore.FirebaseFirestore;
import java.util.HashMap;
import java.util.Map;

/**
 * Created by admin on 01-Aug-18.
 */

public class third extends Activity {

    Button submitbutton;
    EditText name, email, suggestion;
    FirebaseFirestore myfirestore;
    /*FirebaseDatabase firebaseDatabase=FirebaseDatabase.getInstance();
    DatabaseReference mRootReference=firebaseDatabase.getReference();
    DatabaseReference namereference=mRootReference.child("Name");
    DatabaseReference emailreference=mRootReference.child("Email");
    DatabaseReference feedbackreference=mRootReference.child("Feedback");
    //DatabaseReference databaseReference;
    */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.third);
        myfirestore= FirebaseFirestore.getInstance();
        name = (EditText) findViewById(R.id.editText3);
        email = (EditText) findViewById(R.id.editText);
        suggestion = (EditText) findViewById(R.id.editText2);
        submitbutton = (Button) findViewById(R.id.button3);
        submitbutton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (name.getText().toString().length()>0 && email.getText().toString().length()>0 && suggestion.getText().toString().length()>0) {
                    sendsuggestion();
                    Intent myintent3 = new Intent(third.this, second.class);
                    startActivity(myintent3);
                } else {
                    Toast.makeText(getBaseContext(), "Please Enter all the fields!", Toast.LENGTH_LONG).show();
                }
            }
        });
    }
    private void sendsuggestion()
    {
        Map<String, String> usmap=new HashMap<>();
        String username=name.getText().toString().trim();
        usmap.put("Name",username);
        //namereference.setValue(username);
        String useremail=email.getText().toString().trim();
        usmap.put("Email",useremail);
        //emailreference.setValue(useremail);
        String usersuggestion=suggestion.getText().toString();
        usmap.put("Suggestion",usersuggestion);
        //feedbackreference.setValue(usersuggestion);
        String str=myfirestore.collection("MYPrince").document().getId();
        myfirestore.collection("MYPrince").document(str).collection("Suggestions").add(usmap).addOnSuccessListener(new OnSuccessListener<DocumentReference>() {
            @Override
            public void onSuccess(DocumentReference documentReference) {
                Toast.makeText(getBaseContext(),"Your suggestion has been sent. Thanks for your time.",Toast.LENGTH_LONG).show();
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                String error=e.getMessage();
                Toast.makeText(getBaseContext(),"Error"+error,Toast.LENGTH_LONG).show();
            }
        });
    }
}

但是在完成所有这些操作之后，我得到了如下数据库： image2