我昨天添加了firebase身份驗證，它工作正常，但今天在編輯一些文件后它崩潰了。僅當我添加“firebaseAuth =FirebaseAuth.getInstance()”時，應用程序才會崩潰。如果我刪除它，那么一切正常，但現在我無法添加 firebase。SignUp.javaimport android.app.ProgressDialog;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.TextView;import android.widget.Toast;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;public class SignUp extends AppCompatActivity implements View.OnClickListener {    private TextView alreadyRegistered;    private EditText mEmailView;    private EditText mPasswordView;    private Button signup;    private FirebaseAuth firebaseAuth;    ProgressDialog progressDialog;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_sign_up);        progressDialog=new ProgressDialog(this);        mEmailView =  (EditText) findViewById(R.id.email_signup);        mPasswordView = (EditText) findViewById(R.id.password_signup);        signup=(Button)findViewById(R.id.signup);        alreadyRegistered=(TextView)findViewById(R.id.already_registered);//        firebaseAuth =FirebaseAuth.getInstance();////        if(firebaseAuth.getCurrentUser() != null){////            //that means user is already logged in////            //so close this activity////            finish();////////            //and open profile activity////            startActivity(new Intent(getApplicationContext(), Home.class));////        }        alreadyRegistered.setOnClickListener(this);        signup.setOnClickListener(this);    }