我正在尝试使用firebase。而且我遇到了一个问题。我的代码没有错误。但是当我运行它时，我得到了这个错误：
E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException
at com.example.espina.momshie.MainActivity.checkUserValidation(MainActivity.java:159)
at com.example.espina.momshie.MainActivity.access$000(MainActivity.java:28)
at com.example.espina.momshie.MainActivity$1$1.onDataChange(MainActivity.java:71)
at com.google.android.gms.internal.zzdtz.zza(Unknown Source)
at com.google.android.gms.internal.zzdvu.zzbuu(Unknown Source)
at com.google.android.gms.internal.zzdwa.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4960)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
at dalvik.system.NativeStart.main(Native Method)
我不知道为什么会这样，但我怀疑它是toString（）警告。我该如何解决这个问题？
我还没有实现String Builder，所以这个问题与另一个问题有点不同。
顺便说一句，这是我的代码：
package com.example.espina.momshie;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import com.Welcome.Welcome;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
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.loginpack.LoginActivity;
import java.util.Iterator;
public class MainActivity extends AppCompatActivity {
//VIEW AND WIDGETS
Button createUser, moveToLogin;
EditText userEmailEdit, userPasswordEdit;
//FIREBASE AUTH FIELDS
FirebaseAuth nAuth;
FirebaseAuth.AuthStateListener nAuthlistener;
DatabaseReference mDatabaseRef, mUserCheckData;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//ASSIGN ID
createUser = (Button) findViewById(R.id.createUserBtn);
moveToLogin = (Button) findViewById(R.id.moveToLogin);
userEmailEdit = (EditText) findViewById(R.id.emailEditTextCreate);
userPasswordEdit = (EditText) findViewById(R.id.passEditTextCreate);
//ASSIGN INSTANCE
mDatabaseRef = FirebaseDatabase.getInstance().getReference();
mUserCheckData = FirebaseDatabase.getInstance().getReference().child("Users");
nAuth = FirebaseAuth.getInstance();
nAuthlistener = new FirebaseAuth.AuthStateListener(){
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
FirebaseUser user = firebaseAuth.getCurrentUser();
if (user != null) {
final String emailForVer = user.getEmail();
mUserCheckData.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
checkUserValidation(dataSnapshot, emailForVer);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
} else {
}
}
};
//ON CLICK LISTENER
createUser.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
final String userEmailString, userPassString;
userEmailString = userEmailEdit.getText().toString().trim();
userPassString = userPasswordEdit.getText().toString().trim();
if (!TextUtils.isEmpty(userEmailString) && !TextUtils.isEmpty(userPassString))
{
nAuth.createUserWithEmailAndPassword(userEmailString,userPassString).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful())
{
DatabaseReference mChildDatabase = mDatabaseRef.child("Users").push();
String key_user = mChildDatabase.getKey();
mChildDatabase.child("isVerified").setValue("unverified");
mChildDatabase.child("userKey").setValue(key_user);
mChildDatabase.child("emailUser").setValue(userEmailString);
mChildDatabase.child("passWordUser").setValue(userPassString);
Toast.makeText(MainActivity.this, "User Acount Created!", Toast.LENGTH_LONG).show();
startActivity(new Intent(MainActivity.this, Profile.class));
}
else
{
Toast.makeText(MainActivity.this, "User Account Creation Fail", Toast.LENGTH_LONG).show();
}
}
});
}
}
});
//MOVE TO LOGIN
moveToLogin.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view){
startActivity(new Intent(MainActivity.this, LoginActivity.class));
}
});
}
private void checkUserValidation(DataSnapshot dataSnapshot, String emailForVer) {
Iterator iterator = dataSnapshot.getChildren().iterator();
while (iterator.hasNext())
{
DataSnapshot dataUser = (DataSnapshot) iterator.next();
if( dataUser.child("emailUser").getValue().toString().equals(emailForVer))
{
if (dataUser.child("isVerified").getValue().toString().equals("unverified"))
{
Intent in = new Intent( MainActivity.this, Profile.class);
in.putExtra("USER_KEY" , dataUser.child("userKey").getValue().toString());
startActivity(in);
}else
{
startActivity(new Intent(MainActivity.this, Welcome.class));
}
}
}
}
@Override
protected void onStart() {
super.onStart();
nAuth.addAuthStateListener(nAuthlistener);
}
@Override
protected void onStop() {
super.onStop();
nAuth.removeAuthStateListener(nAuthlistener);
}
}
非常感谢你。任何帮助都是预先确定的。