添加电子邮件和密码验证时应用程序崩溃[关闭]

Question

当我尝试使用电子邮件和密码进行验证时，应用程序崩溃了。

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:fitsSystemWindows="true">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:paddingLeft="24dp"
        android:paddingTop="56dp"
        android:paddingRight="24dp">



        <EditText
            android:id="@+id/input_email"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Email"
            android:inputType="textEmailAddress" />

        <EditText
            android:id="@+id/input_password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Password"
            android:inputType="textPassword" />

        <android.support.v7.widget.AppCompatButton
            android:id="@+id/btn_login"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="24dp"
            android:layout_marginBottom="24dp"
            android:padding="12dp"
            android:onClick="onRegister"
            android:text="Login" />


    </LinearLayout>
</ScrollView>

main_activity.Java

在这里我试图通过电子邮件和密码验证添加用户，但每当我添加此firebase代码应用程序崩溃。

package com.example.login;

import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
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.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;

public class MainActivity extends AppCompatActivity {

    EditText email = findViewById(R.id.input_email);
    EditText pass = findViewById(R.id.input_password);

    private FirebaseAuth mAuth;


    @Override
    protected void onStart() {
        super.onStart();

        FirebaseUser currentUser = mAuth.getCurrentUser();
        Toast.makeText(MainActivity.this, "already registered"+currentUser,Toast.LENGTH_SHORT).show();
        Log.i("already","already in");



    }



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

        mAuth = FirebaseAuth.getInstance();



    }
    public void onRegister(View view){

        String myemail = email.getText().toString();
        String mypass = pass.getText().toString();

        mAuth.createUserWithEmailAndPassword(myemail, mypass)
                .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                            // Sign in success, update UI with the signed-in user's information
                            Toast.makeText(MainActivity.this,"successfully registered",Toast.LENGTH_SHORT).show();


                        } else {
                            // If sign in fails, display a message to the user.

                            Toast.makeText(MainActivity.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        }

                        // ...
                    }
                });
    }
}

APP-gradle这个

它也在gradle文件中给出了一些错误，比如com.android.support应该有相同的verison。

*

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.login"
        minSdkVersion 22
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.google.firebase:firebase-auth:16.2.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

}

Answer 1

在你的MainActivity你已经初始化你的view错误，声明并初始化你的EditTexts字段如下

public class MainActivity extends AppCompatActivity {

    private EditText email;
    private EditText pass;

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

        email = findViewById(R.id.input_email);
        pass = findViewById(R.id.input_password);
    }
}

总是记得在Activity方法调用之后将视图附加到setContentView(R.layout.activity_main);之后初始化视图字段，这会附加你的视图，否则你会得到null指针异常，就像我猜你现在得到的那样