检查字符串为NULL还是EMPTY

Question

Hi I understand there are duplicates like ( Firebase Registration, Given String is empty or null ) and ( I keep getting"java.lang.IllegalArgumentException: Given String is empty or null" and it has something to do with auth = FirebaseAuth.getInstance();" ).

Both articles mentioned solution about the api_key. I have checked mine and they were already exist so I strongly believe it is no longer due to that. As such I researched further and found out that I need to have something to check empty so I got these ( Check whether a string is not null and not empty ) and ( Checking if a string is empty or null in Java ).

I did tried their solutions but to no avail - I am still getting the above-mentioned error. I coded it using my instincts and the guides given but I am still not entirely sure if I did it right or not. As in, whether the mistakes are the codes itself or I placed them wrongly.

Can anyone help me to check and provide guidance so I can correct the mistake? NOTE: I'm using Firebase for authentication.

Below are my codes:

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();
    }
}

}

Error trace

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

Be careful with getText() . You need to check the result of getText() , and not the subsequent 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
}

This is because, for whatever reason, if getText() is null , then toString() is called on the EditText instance itself, which will return the full classname of EditText and that instance's hashcode.

Also, you should be calling the result of checkEmptyCredentials() before you call validate() , not after you attempt the login. This is likely the cause of your crash, while the above will fix an error you haven't yet run into.

Answer 2

firebaseAuth.signInWithEmailAndPassword function does not allow null or empty text. So you have to make sure that these fields are not null & not empty.

For easier check, i suggest you using this class https://developer.android.com/reference/android/text/TextUtils . It has a function isEmpty() which can check null and empty in 1 call.

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();

                    }