检查字符串为NULL还是EMPTY

Question

嗨，我知道有重复的内容，例如（ Firebase注册，给定的字符串为空或null ）和（ 我一直在获取“ java.lang.IllegalArgumentException：给定的字符串为空或null”，这与auth = FirebaseAuth.getInstance（ ）;“ ）。

这两篇文章都提到了有关api_key的解决方案。 我已经检查了我的地雷，它们已经存在，所以我坚信它不再是这个原因。 这样，我进行了进一步研究，发现我需要检查一下是否为空，因此得到了这些内容（ 检查字符串是否不为null且不为空 ）和（ 检查Java中的字符串为空还是null ）。

我确实尝试了他们的解决方案，但无济于事-我仍然遇到上述错误。 我使用自己的直觉和给出的指南对其进行了编码，但是我仍然不确定是否正确。 就像错误一样，无论错误是代码本身还是我错误地放置了它们。

谁能帮助我检查并提供指导，以便我纠正错误？ 注意：我正在使用Firebase进行身份验证。

以下是我的代码：

package com.example.run_h.boav2;

import android.app.ProgressDialog;
import android.content.Intent;
import android.hardware.usb.UsbRequest;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
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;
import com.google.firebase.auth.FirebaseUser;

public class MainActivity extends AppCompatActivity {

private EditText Username;
private EditText Password;
private TextView Info;
private Button Login;
private int counter = 3;
private Button userRegistration;
private FirebaseAuth firebaseAuth;
private ProgressDialog progressDialog;
private TextView forgotPassword;

String name, password;

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

    Username = (EditText)findViewById(R.id.etUsername);
    Password = (EditText)findViewById(R.id.etPassword);
    Info = (TextView)findViewById(R.id.tvInfo);
    Login = (Button)findViewById(R.id.btnLogin);
    userRegistration = (Button)         
    findViewById(R.id.tvRegister);
    forgotPassword = 
    (TextView)findViewById(R.id.tvForgotPassword);

    Info.setText("# of Attempts Left: 3");


    firebaseAuth = FirebaseAuth.getInstance();
    FirebaseUser user = firebaseAuth.getCurrentUser();

    progressDialog = new ProgressDialog(this);

    //user has logged in and never once logged out. auto 
    bring to the secondactivity (dashboard) page.
    if(user != null){
        finish();
        startActivity(new Intent(MainActivity.this, 
    SecondActivity.class));
    }

    Login.setOnClickListener(new View.OnClickListener() 
   {
        @Override
        public void onClick(View view) {
            validate(Username.getText().toString(), 
   Password.getText().toString());
        }
    });

    userRegistration.setOnClickListener(new 
   View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivity(new Intent(MainActivity.this, 
   RegistrationActivity.class));
        }
    });

    forgotPassword.setOnClickListener(new 
   View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivity(new Intent(MainActivity.this, 
   PasswordActivity.class ));
        }
    });
}

private void validate(String userName, String 
userPassword){

    progressDialog.setMessage("Please hold on. We are 
testing your patience!");
    progressDialog.setProgressStyle(progressDialog.STYLE_SPINNER);
    progressDialog.show();

    firebaseAuth.signInWithEmailAndPassword(userName, 
 userPassword).addOnCompleteListener(new 
 OnCompleteListener<AuthResult>() {
        @Override
        public void onComplete(@NonNull Task<AuthResult> 
 task) {
            if(task.isSuccessful()){
                progressDialog.dismiss();
                checkEmailVerification();
            }
            else{
   //Toast.makeText(MainActivity.this, "Login failed. 
   Incorrect username or password. Please try again.", 
   Toast.LENGTH_SHORT).show();
                progressDialog.dismiss();
                checkEmptyCredentials();
                counter--;
                Info.setText("# of Attempts Left: " + counter);
                if(counter == 0){
                    Login.setEnabled(false);
                    startActivity(new Intent(MainActivity.this, PasswordActivity.class)); //forces user to reset password
                }
            }
        }
    });
}

private Boolean checkEmptyCredentials(){
    Boolean result = false;

    name = Username.getText().toString();
    password = Password.getText().toString();

    if(name != null && name.isEmpty() || password != null && password.isEmpty()){
        Toast.makeText(this, "All fields must not be blank.", Toast.LENGTH_SHORT).show();
    }else{
        result = true;
    }
    return result;
}


private void checkEmailVerification(){
    FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
    Boolean emailflag = firebaseUser.isEmailVerified();

    if(emailflag){
        finish();
        startActivity(new Intent(MainActivity.this, Main2Activity.class));
    }else{
        Toast.makeText(this, "Please verify your email and account to login.", Toast.LENGTH_SHORT).show();
        firebaseAuth.signOut();
    }
}

}

错误跟踪

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.run_h.boav2, PID: 27092
java.lang.IllegalArgumentException: Given String is empty or null
    at com.google.android.gms.common.internal.Preconditions.checkNotEmpty(Unknown Source)
    at com.google.firebase.auth.FirebaseAuth.signInWithEmailAndPassword(Unknown Source)
    at com.example.run_h.boav2.MainActivity.validate(MainActivity.java:89)
    at com.example.run_h.boav2.MainActivity.access$200(MainActivity.java:21)
    at com.example.run_h.boav2.MainActivity$1.onClick(MainActivity.java:64)
    at android.view.View.performClick(View.java:5697)
    at android.widget.TextView.performClick(TextView.java:10814)
    at android.view.View$PerformClick.run(View.java:22526)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:158)
    at android.app.ActivityThread.main(ActivityThread.java:7229)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

Answer 1

使用getText()要小心。 您需要检查getText()的结果，而不是随后的toString() ：

CharSequence text = someEditText.getText();
if (text == null) {
    //do what you do when the text is null or empty
}

String stringText = text.toString();
if (stringText.isEmpty()) {
    //do what you do when the text is null or empty
}

这是因为无论出于何种原因，如果getText()为null ，则在EditText实例本身上调用toString() ，这将返回EditText的完整类名以及该实例的哈希码。

此外，您应该呼吁的结果checkEmptyCredentials()调用之前 validate()而不是之后尝试登录。 这可能是导致崩溃的原因，而以上内容将修复您尚未遇到的错误。

Answer 2

firebaseAuth.signInWithEmailAndPassword函数不允许使用null或空文本。 因此，您必须确保这些字段不为null和不为空。

为了便于检查，我建议您使用此类https://developer.android.com/reference/android/text/TextUtils 。 它具有一个isEmpty()函数，可以在一次调用中检查null和empty。

private void validate(String userName, String userPassword){
if (TextUtils.isEmpty(userName)) return; // userName null or empty. We do not process it.
if (TextUtils.isEmpty(userPassword)) return; // userPassword null or empty. We do not process it.

    progressDialog.setMessage("Please hold on. We are 
testing your patience!");
    progressDialog.setProgressStyle(progressDialog.STYLE_SPINNER);
    progressDialog.show();

    firebaseAuth.signInWithEmailAndPassword(userName, 
 userPassword).addOnCompleteListener(new 
 OnCompleteListener<AuthResult>() {
        @Override
        public void onComplete(@NonNull Task<AuthResult> 
 task) {
            if(task.isSuccessful()){
                progressDialog.dismiss();
                checkEmailVerification();
            }
            else{
   //Toast.makeText(MainActivity.this, "Login failed. 
   Incorrect username or password. Please try again.", 
   Toast.LENGTH_SHORT).show();
                progressDialog.dismiss();
                //checkEmptyCredentials();  //We need to check before signin. So you can replace my code lines above with this function.
                counter--;
                Info.setText("# of Attempts Left: " + counter);
                if(counter == 0){
                    Login.setEnabled(false);
                    startActivity(new Intent(MainActivity.this, PasswordActivity.class)); //forces user to reset password
                }
            }
        }
    });
}

Answer 3

if (!password.getText().toString().isEmpty()&&!email.getText().toString().isEmpty()) {

    firebaseAuth.signInWithEmailAndPassword(name, password).addOnCompleteListener(Login.this, new OnCompleteListener<AuthResult>() {
        @Override
        public void onComplete(@NonNull Task<AuthResult> task) {
            if (!task.isSuccessful()) {
                // there was an error
                Toast.makeText(Login.this, "Something Went wrong", Toast.LENGTH_SHORT).show();

            } else {
                checkEmailVerification();
            } }
    });

}

                    } else {
                    Toast.makeText(this, "All fields must not be blank.", Toast.LENGTH_SHORT).show();

                    }