android - Firebase 数据库无法更新

Question

有一个设置选项，您可以在其中设置您的姓名和地址。它应该在当前用户的数据库中更新。每当输入信息并按下“确认”按钮时，应用程序就会崩溃。请帮我调试一下。我附上了一张数据库应该是什么样子的图片。

Here is what the database looks like

下面是logcat

2020-05-09 18:42:26.825 749-749/com.example.macdate E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.macdate, PID: 749
    java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.tasks.Task com.google.firebase.database.DatabaseReference.updateChildren(java.util.Map)' on a null object reference
        at com.example.macdate.SettingsActivity.saveUserInformation(SettingsActivity.java:143)
        at com.example.macdate.SettingsActivity.access$000(SettingsActivity.java:38)
        at com.example.macdate.SettingsActivity$2.onClick(SettingsActivity.java:86)
        at android.view.View.performClick(View.java:6294)
        at android.view.View$PerformClick.run(View.java:24770)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

下面是需要注意的代码

package com.example.macdate;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;

import com.bumptech.glide.Glide;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
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.UploadTask;

import java.io.ByteArrayOutputStream;
import java.util.HashMap;
import java.util.Map;
import java.io.IOException;


public class SettingsActivity extends AppCompatActivity {

    private EditText mNameField, mPhoneField;

    private Button mBack, mConfirm;

    private ImageView mProfileImage;

    private FirebaseAuth mAuth;
    private DatabaseReference mCustomerDatabase;

    private String userId, name, phone, profileImageUrl;

    private Uri resultUri;

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

        String userSex = getIntent().getExtras().getString("userSex");
        mNameField = (EditText) findViewById(R.id.name);
        mPhoneField = (EditText) findViewById(R.id.phone);

        mProfileImage = (ImageView) findViewById(R.id.profileImage);

        mBack = (Button) findViewById(R.id.back);
        mConfirm = (Button) findViewById(R.id.confirm);

        mAuth = FirebaseAuth.getInstance();
        FirebaseUser mFirebaseUser = mAuth.getCurrentUser();
        if(mFirebaseUser != null && userSex != null) {
            userId = mFirebaseUser.getUid();
            mCustomerDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(userSex).child(userId);
            getUserInfo();
        }

        mProfileImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(Intent.ACTION_PICK);
                intent.setType("image/*");
                startActivityForResult(intent, 1);
            }
        });
        mConfirm.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                saveUserInformation();
            }
        });
        mBack.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                finish();
                return;
            }
        });
    }


    private void getUserInfo() {
        mCustomerDatabase.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                if(dataSnapshot.exists() && dataSnapshot.getChildrenCount()>0){
                    Map<String, Object> map = (Map<String, Object>) dataSnapshot.getValue();
                    if(map.get("name")!=null){
                        name = map.get("name").toString();
                        mNameField.setText(name);
                    }
                    if(map.get("phone")!=null){
                        phone = map.get("phone").toString();
                        mPhoneField.setText(phone);
                    }

                    if(map.get("profileImageUrl")!=null){
                        profileImageUrl = map.get("profileImageUrl").toString();
                        switch(profileImageUrl){
                            case "default":
                                Glide.with(getApplication()).load(R.mipmap.ic_launcher).into(mProfileImage);
                                break;
                            default:
                                Glide.with(getApplication()).load(profileImageUrl).into(mProfileImage);
                                break;
                        }
                    }
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

    }

    private void saveUserInformation() {
        name = mNameField.getText().toString();
        phone = mPhoneField.getText().toString();

        Map userInfo = new HashMap();
        userInfo.put("name", name);
        userInfo.put("phone", phone);
        mCustomerDatabase.updateChildren(userInfo);
        if(resultUri != null){
            StorageReference filepath = FirebaseStorage.getInstance().getReference().child("profileImages").child(userId);
            Bitmap bitmap = null;

            try {
                bitmap = MediaStore.Images.Media.getBitmap(getApplication().getContentResolver(), resultUri);
            } catch (IOException e) {
                e.printStackTrace();
            }

            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.JPEG, 20, baos);
            byte[] data = baos.toByteArray();
            UploadTask uploadTask = filepath.putBytes(data);
            uploadTask.addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    finish();
                }
            });
            uploadTask.addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
                @Override
                public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
                    Task<Uri> downloadUrl = taskSnapshot.getMetadata().getReference().getDownloadUrl();

                    Map userInfo = new HashMap();
                    userInfo.put("profileImageUrl", downloadUrl.toString());
                    mCustomerDatabase.updateChildren(userInfo);

                    finish();
                    return;
                }
            });
        }else{
            finish();
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == 1 && resultCode == Activity.RESULT_OK){
            final Uri imageUri = data.getData();
            resultUri = imageUri;
            mProfileImage.setImageURI(resultUri);
        }
    }

}*

Answer 1

错误信息:

java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.tasks.Task com.google.firebase.database.DatabaseReference.updateChildren(java.util.Map)' on a null object reference

告诉您 mCustomerDatabase 为空。

mCustomerDatabase 为空，因为您在开始使用它之前没有为其分配值。查看执行分配的代码:

        FirebaseUser mFirebaseUser = mAuth.getCurrentUser();
        if(mFirebaseUser != null && userSex != null) {
            userId = mFirebaseUser.getUid();
            mCustomerDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(userSex).child(userId);
            getUserInfo();
        }

mCustomerDatabase 在某些情况下不会获得值。您将必须调试您的代码以找出为什么 mFirebaseUser 或 userSex 为空。