显示java.lang.NullPointerException：尝试调用虚拟方法 'java.lang.String中com.google.firebase.auth.FirebaseUser.getUid（）'

Question

Process: com.example.vicevirus.myapplication, PID: 13471 
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference 
       at com.example.vicevirus.myapplication.RegisterActivity$1.onComplete(RegisterActivity.java:48) 
       at com.google.android.gms.tasks.zzc$1.run(Unknown Source) 
       at android.os.Handler.handleCallback(Handler.java:751) 
       at android.os.Handler.dispatchMessage(Handler.java:95) 
       at android.os.Looper.loop(Looper.java:154) 
       at android.app.ActivityThread.main(ActivityThread.java:6119) 
       at java.lang.reflect.Method.invoke(Native Method) 
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

这是机器人监视器上。我该如何解决这个问题？

package com.example.vicevirus.myapplication; 

import android.app.ProgressDialog; 
     import android.support.annotation.NonNull; 
     import android.support.v7.app.AppCompatActivity; 
     import android.os.Bundle; 
     import android.view.View; 
     import android.widget.EditText; 
     import android.widget.Toast; 
     import com.google.android.gms.tasks.OnCompleteListener; 
     import com.google.android.gms.tasks.OnSuccessListener; 
     import com.google.android.gms.tasks.Task; 
     import com.google.firebase.auth.AuthResult; 
     import com.google.firebase.auth.FirebaseAuth; 
     import com.google.firebase.database.DatabaseReference; 
     import com.google.firebase.database.FirebaseDatabase; 

public class RegisterActivity extends AppCompatActivity { 
    private EditText email,name,password; 
    DatabaseReference databaseReference; 
    FirebaseAuth mAuth; 
    private DatabaseReference userIdRef; 
    ProgressDialog registerDialog; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_register); 
     email=(EditText)findViewById(R.id.email); 
     name=(EditText)findViewById(R.id.name); 
     password=(EditText)findViewById(R.id.password); 
     databaseReference= FirebaseDatabase.getInstance().getReference().child("chat_users"); 
     mAuth=FirebaseAuth.getInstance(); 
     registerDialog=new ProgressDialog(this); 
     registerDialog.setMessage("Registering.."); 
    } 
    public void submit(View view) { 
     registerDialog.show(); 
     mAuth.createUserWithEmailAndPassword(email.getText().toString(),password.getText().toString()).addOnCompleteListener(this, new OnCompleteListener<AuthResult>() { 
      @Override 
      public void onComplete(@NonNull Task<AuthResult> task) { 
       if(task.isComplete()) 
       { 
        registerDialog.dismiss(); 
        Toast.makeText(getApplicationContext(),"Registered successfully",Toast.LENGTH_SHORT).show(); 
        userIdRef=databaseReference.child(mAuth.getCurrentUser().getUid()); 
        userIdRef.child("name").setValue(name.getText().toString()); 
        finish(); 
       } 
       registerDialog.dismiss(); 
      } 
     }); 
    } 
} 

Answer 1

这个问题似乎是您的用户尚未登陆，甚至注册。所以调用mAuth.getCurrentUser()返回null。

查看this page of the FireBase documentation了解您需要如何实施注册用户。这可能是失败的。检查task.isSuccessful()是必要的，以检查这一点。