logo标签列表

检查Firebase数据库中是否存在特定值

javaandroidfirebasefirebase-realtime-database
4

我正在使用Java和Firebase开发一个Android应用程序。以下是我的代码，用于创建用户个人资料并将数据存储在Firebase数据库中。

package com.eNotification.getnotify;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import android.Manifest;
import android.content.ContentResolver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.ConnectivityManager;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.text.TextUtils;
import android.view.View;
import android.webkit.MimeTypeMap;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

import com.eNotification.getnotify.utils.Utils;
import com.google.android.gms.tasks.Continuation;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.textfield.TextInputEditText;
import com.google.android.material.textfield.TextInputLayout;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.StorageTask;
import com.google.firebase.storage.UploadTask;
import com.mikhaellopez.circularimageview.CircularImageView;
import com.squareup.picasso.Picasso;
import com.theartofdev.edmodo.cropper.CropImage;
import com.theartofdev.edmodo.cropper.CropImageView;

import java.util.ArrayList;
import java.util.List;

public class MainActivityCreateProfile extends AppCompatActivity {

    private static final int STORAGE_PERMISSION_CODE=1;

    private TextInputLayout dUsername,dRegNo;
    private TextInputEditText dEditUsername,dEditRegNo;
    private CircularImageView dProfileImage;
    private Spinner dCourse;
    private TextView selected;
    private Button dDoneBtn;

    private String uid,email;
    private String select="Select course",maxid,s;
    private Uri selectedImage=null,uri;

    private FirebaseDatabase firebaseDatabase;
    private DatabaseReference databaseReference;
    private StorageReference storageReference;
    private FirebaseStorage firebaseStorage;

    private StorageTask mUploadTask;

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

        firebaseDatabase = FirebaseDatabase.getInstance();
        firebaseStorage = FirebaseStorage.getInstance();
        databaseReference = FirebaseDatabase.getInstance().getReference().child("USERS");
        storageReference = firebaseStorage.getReference("Profile images");

        uid = getIntent().getStringExtra("uid");
        email = getIntent().getStringExtra("email");

        dProfileImage = findViewById(R.id.dProfileImg);
        dUsername = findViewById(R.id.dUsername);
        dRegNo = findViewById(R.id.dRegNo);
        dEditUsername = findViewById(R.id.dEditUsername);
        dEditRegNo = findViewById(R.id.dEditReg);
        selected = findViewById(R.id.course);
        dCourse = findViewById(R.id.dCourse);

        List<String> categories = new ArrayList<>();
        categories.add(0,"Select course");
        categories.add("BCA");
        categories.add("BBA");
        categories.add("BCOM");
        categories.add("BA");

        ArrayAdapter<String> dataAdapter;
        dataAdapter = new  ArrayAdapter(this,android.R.layout.simple_spinner_item,categories);

        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        dCourse.setAdapter(dataAdapter);
        dCourse.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            //    if (parent.getItemAtPosition(position).equals("Select course")){
              //      Toast.makeText(MainActivityCreateProfile.this, "Select the course", Toast.LENGTH_SHORT).show();
                //} else {
                    selected.setText(parent.getSelectedItem().toString());
                //}
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {
                Toast.makeText(MainActivityCreateProfile.this, "Select a course", Toast.LENGTH_SHORT).show();
            }
        });

        dDoneBtn = findViewById(R.id.dDoneBtn);

        dDoneBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                inputValidation();
            }
        });

        dProfileImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ContextCompat.checkSelfPermission(MainActivityCreateProfile.this,
                        Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
                    Toast.makeText(MainActivityCreateProfile.this, "You have already granted permission", Toast.LENGTH_SHORT).show();
                    SelectImage();
                }  else {
                    requestStoragePermission();
                }
            }
        });
    }

    private void requestStoragePermission() {
        if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivityCreateProfile.this, Manifest.permission.READ_EXTERNAL_STORAGE)) {
            new AlertDialog.Builder(this)
                    .setTitle("Permission needed")
                    .setMessage("This Permission is needed for uploading the Image")
                    .setPositiveButton("ok", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            ActivityCompat.requestPermissions(MainActivityCreateProfile.this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, STORAGE_PERMISSION_CODE);
                        }
                    })
                    .setNegativeButton("cancel", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.dismiss();
                        }
                    })
                    .create().show();
        } else {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, STORAGE_PERMISSION_CODE);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == STORAGE_PERMISSION_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Permission granted", Toast.LENGTH_SHORT).show();
                SelectImage();
            } else {
                Toast.makeText(this, "Permission denied", Toast.LENGTH_SHORT).show();

            }
        }
    }

    public void SelectImage() {
        CropImage.activity()
                .setGuidelines(CropImageView.Guidelines.ON)
                .setAspectRatio(1,1)
                .start(this);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == CropImage.CROP_IMAGE_ACTIVITY_REQUEST_CODE) {
            CropImage.ActivityResult result = CropImage.getActivityResult(data);
            if (resultCode == RESULT_OK) {
                selectedImage = result.getUri();
                Picasso.get().load(selectedImage).into(dProfileImage);
            } else if (resultCode == CropImage.CROP_IMAGE_ACTIVITY_RESULT_ERROR_CODE) {
                Exception error = result.getError();
            }
        }
    }

    private void inputValidation() {
        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        if (cm.getActiveNetworkInfo() != null && cm.getActiveNetworkInfo().isConnected()) {
            //Username validation
            if (!Utils.inputValidation(dEditUsername)) {
                Toast.makeText(this, "Enter the username", Toast.LENGTH_SHORT).show();
                return;
            } else if (!Utils.usernameVerify(dEditUsername)) {
                Toast.makeText(this, "A Username should not exceed 15 characters", Toast.LENGTH_SHORT).show();
                return;
            } else {
                dUsername.setErrorEnabled(false);
            }

            //Reg no Validation
            if (!Utils.inputValidation(dEditRegNo)) {
                Toast.makeText(this, "Enter the Register No", Toast.LENGTH_SHORT).show();
                return;
            } else if (!Utils.regNoVerify(dEditRegNo)) {
                Toast.makeText(this, "Enter correct Register No", Toast.LENGTH_SHORT).show();
                return;
            }
            createProfile();
        }else {
            Toast.makeText(this, "Check internet connection", Toast.LENGTH_SHORT).show();
        }
    }

    public String GetFileExtension(Uri uri) {

        ContentResolver contentResolver = getContentResolver();
        MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
        return mimeTypeMap.getExtensionFromMimeType(contentResolver.getType(uri)) ;

    }

    private void createProfile(){
        final String username = dEditUsername.getText().toString();
        final String regNo = dEditRegNo.getText().toString();
        final String course = dCourse.getSelectedItem().toString();
        maxid = databaseReference.push().getKey();

        if (!TextUtils.isEmpty(username) && (!TextUtils.isEmpty(regNo))) {
            if (!course.equals(select)) {
                databaseReference.orderByChild("regNo").equalTo(regNo).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                            if (dataSnapshot.exists()){
                                Toast.makeText(MainActivityCreateProfile.this, "Reg no. exist", Toast.LENGTH_SHORT).show();
                            } else {
                                s = "https://firebasestorage.googleapis.com/v0/b/getnotify-da5c1.appspot.com/o/Permanent%2Fuser.png?alt=media&token=017d9013-ede2-49c7-b53b-6e96d90e3398";
                                UserDetails userDetails = new UserDetails(s, username, regNo, course, email);
                                databaseReference.child(maxid).setValue(userDetails);
                                Toast.makeText(MainActivityCreateProfile.this, "Upload Successful", Toast.LENGTH_SHORT).show();
                            }
                        }


                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {
                        Toast.makeText(MainActivityCreateProfile.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
                    }
                });
            } else {
                Toast.makeText(this, "Select a course", Toast.LENGTH_SHORT).show();
            }
        } else {
            Toast.makeText(this, "Enter username and Register No.", Toast.LENGTH_SHORT).show();
        }
    }
}

我面临一个问题，想要检查数据库中是否已存在注册号，以下是用于检查的代码：

databaseReference.orderByChild("regNo").equalTo(regNo).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                            if (dataSnapshot.exists()){
                                Toast.makeText(MainActivityCreateProfile.this, "Reg no. exist", Toast.LENGTH_SHORT).show();
                            } else {
                                s = "https://firebasestorage.googleapis.com/v0/b/getnotify-da5c1.appspot.com/o/Permanent%2Fuser.png?alt=media&token=017d9013-ede2-49c7-b53b-6e96d90e3398";
                                UserDetails userDetails = new UserDetails(s, username, regNo, course, email);
                                databaseReference.child(maxid).setValue(userDetails);
                                Toast.makeText(MainActivityCreateProfile.this, "Upload Successful", Toast.LENGTH_SHORT).show();
                            }
                        }


                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {
                        Toast.makeText(MainActivityCreateProfile.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
                    }
                });

代码运行正确。它检测数据库中的值是否存在，如果存在，则显示Toast消息“Reg No. exist”；如果不存在，则成功在数据库中创建子项，但它仍然显示Toast消息“Reg No. exist”，而不是“Upload successful”。由于我对这些概念比较新，如果您知道任何信息，请帮忙解决。
数据库节点: https://istack.dev59.com/Szoyt.webp
请粘贴您的数据库节点图像。 - Hasan Bou Taam
尝试在DocumentReference上使用get而不是addValueEventListener。 - Hussain
@svi.data 图像已添加 - Dhanush Ambig
将图像添加到您的问题中，而不是链接。 - Hasan Bou Taam
@Hussain，你能简要解释一下吗？ - Dhanush Ambig
2个回答
2
根据Hussain的回答，每当您的数据库发生更改时，都会调用addValueEventListener()，为了解决这种情况，您可以调用addListenerForSingleValueEvent()。它只会被调用一次。
除此之外，在实时数据库中没有获取选项。
databaseReference.orderByChild("regNo").equalTo(regNo)
    .addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.exists()) {
                //Do what you want to try
            }else{
                //Create New Node in Database
            }
        }

        @Override
            public void onCancelled(DatabaseError databaseError) {

        }
    });
请告诉我如何添加 .whereEqualTo。 - Dhanush Ambig
@Ashsh 你说要添加 databaseReference.whereEqualTo，但我无法使用它。Android Studio 在 .whereEqualTo 上显示错误。 - Dhanush Ambig
@DhanushAmbig 我不小心给了你Firestore查询，因为我现在没有使用IDE。 - Ashish
1
这里可能出现问题的代码是这样的。您正在尝试使用addValueEventListener在用户databaseReference上检查regno是否存在。
根据Android文档，addValueEventListener执行以下操作：
添加一个监听器以便在此位置的数据发生更改时进行更改。每次数据更改时，都会使用不可变的数据快照调用您的监听器。
因此，当dataSnapshot不存在时，它会创建一个新节点，最终addValueEventListener再次触发，而您的toast将打印Reg no. exist。
你可以做的是：
databaseReference
    .child(regNo)
    .addListenerForSingleValueEvent(new ValueEventListenerAdapter() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            if (snapshot.exists()) {
               // Document exists
            } else {
               // Do something
            }
        }
    });
.whereEqualTo不起作用。如何添加它。 - Dhanush Ambig
网页内容由stack overflow 提供, 点击上面的
可以查看英文原文，
原文链接