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首页 > 解决方案 > 尝试在 SignUpActivity.onCreate 的空对象引用上调用虚拟方法 'void android.widget.Button.setOnClickListener

java - 尝试在 SignUpActivity.onCreate 的空对象引用上调用虚拟方法 'void android.widget.Button.setOnClickListener

问题描述

我试图点击登录活动中的注册按钮，但是当点击应用程序中的按钮时，它会跳出并给出这样的错误，确实有类似于我问的问题，但我真的尝试了所有您提出的解决方案，但对我不起作用。

错误：

> E/AndroidRuntime: FATAL EXCEPTION: main
>     Process: com.fivenine.shareit, PID: 17033
>     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.fivenine.shareit/com.fivenine.shareit.AccountActivity.SignUpActivity}:
> java.lang.NullPointerException: Attempt to invoke virtual method 'void
> android.widget.Button.setOnClickListener(android.view.View$OnClickListener)'
> on a null object reference
>         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2747)
>         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2808)
>         at android.app.ActivityThread.-wrap12(ActivityThread.java)
>         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1541)
>         at android.os.Handler.dispatchMessage(Handler.java:102)
>         at android.os.Looper.loop(Looper.java:165)
>         at android.app.ActivityThread.main(ActivityThread.java:6375)
>         at java.lang.reflect.Method.invoke(Native Method)
>         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:912)
>         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:802)
>      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void
> android.widget.Button.setOnClickListener(android.view.View$OnClickListener)'
> on a null object reference
>         at com.fivenine.shareit.AccountActivity.SignUpActivity.onCreate(SignUpActivity.java:44)
>         at android.app.Activity.performCreate(Activity.java:6845)
>         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
>         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2700)
>         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2808) 
>         at android.app.ActivityThread.-wrap12(ActivityThread.java) 
>         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1541) 
>         at android.os.Handler.dispatchMessage(Handler.java:102) 
>         at android.os.Looper.loop(Looper.java:165) 
>         at android.app.ActivityThread.main(ActivityThread.java:6375) 
>         at java.lang.reflect.Method.invoke(Native Method) 
>         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:912) 
>         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:802)

这是 SignUpActivity.java：

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.ProgressBar;
import android.widget.Toast;

import com.fivenine.shareit.MainActivity;
import com.fivenine.shareit.R;
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 SignUpActivity extends AppCompatActivity {

    private EditText inputEmail, inputPassword;
    private Button btnSignIn, btnSignUp, btnResetPassword;
    private ProgressBar progressBar;
    private FirebaseAuth auth;

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

        //Get Firebase auth instance

        auth = FirebaseAuth.getInstance();

        btnSignIn = (Button) findViewById(R.id.sign_in_button);
        btnSignUp = (Button) findViewById(R.id.sign_up_button);
        inputEmail = (EditText) findViewById(R.id.email);
        inputPassword = (EditText) findViewById(R.id.password);
        progressBar = (ProgressBar) findViewById(R.id.progressBar);
        btnResetPassword = (Button) findViewById(R.id.btn_reset_password);

        btnResetPassword.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View view) {
                startActivity(new Intent(SignUpActivity.this, ResetPasswordActivity.class));
            }
        });

        btnSignIn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                finish();
            }
        });

        btnSignUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String email = inputEmail.getText().toString().trim();
                String password = inputPassword.getText().toString().trim();

                if (TextUtils.isEmpty(email)){
                    Toast.makeText(getApplicationContext(), "Enter email address!",
                            Toast.LENGTH_SHORT).show();
                    return;
                }

                if (TextUtils.isEmpty(password)){
                    Toast.makeText(getApplicationContext(), "Enter password!",
                            Toast.LENGTH_SHORT).show();
                    return;
                }

                if (password.length() < 6){
                    Toast.makeText(getApplicationContext(), "Password too short,enter minimum 6 characters!",
                            Toast.LENGTH_SHORT).show();
                    return;
                }

                progressBar.setVisibility(View.VISIBLE);
                //create user
                auth.createUserWithEmailAndPassword(email, password)
                        .addOnCompleteListener(SignUpActivity.this, new OnCompleteListener<AuthResult>() {
                            @Override
                            public void onComplete(@NonNull Task<AuthResult> task) {
                                Toast.makeText(SignUpActivity.this,"createUserWithEmail:onComplete:" + task.isSuccessful(),
                                        Toast.LENGTH_SHORT).show();
                                progressBar.setVisibility(View.GONE);

                                if(!task.isSuccessful()){
                                    Toast.makeText(SignUpActivity.this, "Authenticaton faled." + task.getException(),
                                            Toast.LENGTH_SHORT).show();
                                }else{
                                    startActivity(new Intent(SignUpActivity.this,
                                            MainActivity.class));
                                    finish();
                                }
                            }
                        });
            }
        });
    }

    @Override
    protected void onResume(){
        super.onResume();
        progressBar.setVisibility(View.GONE);
    }
}

activity_sign_up.xml：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.fivenine.shareit.AccountActivity.SignUpActivity">


    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="@drawable/gradient_6"
        android:gravity="center"
        android:orientation="vertical"
        android:padding="@dimen/activity_horizontal_margin">

        <ImageView
            android:layout_width="75dp"
            android:layout_height="80dp"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="30dp"
            android:contentDescription=""
            android:src="@drawable/profile"
            tools:ignore="ContentDescription" />

        <EditText
            android:id="@+id/email"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/email"
            android:inputType="textEmailAddress"
            android:maxLines="1"
            android:textColor="@android:color/black"/>

        <EditText
            android:id="@+id/password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:focusableInTouchMode="true"
            android:hint="@string/hint_password"
            android:imeActionId="@integer/login"
            android:imeOptions="actionUnspecified"
            android:inputType="textPassword"
            android:maxLines="1"
            android:textColor="@android:color/black"/>
        <Button
            android:id="@+id/sign_up_button"
            style="?android:textAppearanceSmall"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dip"
            android:background="@drawable/btn_corner_pink_gradient"
            android:text="@string/action_sign_in_short"
            android:textColor="@android:color/white"
            android:textStyle="bold"/>

       <!-- <Button
            android:id="@+id/btn_reset_password"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dip"
            android:background="@null"
            android:text="@string/btn_forgot_password"
            android:textAllCaps="false"
            android:textColor="@color/colorAccent"/> -->

        <!-- Link to login screen -->

        <Button
            android:id="@+id/sign_in_button"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dip"
            android:background="@null"
            android:text="@string/btn_link_to_login"
            android:textAllCaps="false"
            android:textColor="@color/colorWhite"
            android:textSize="15sp"/>

    </LinearLayout>

    <ProgressBar
        android:id="@+id/progressBar"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_gravity="center|bottom"
        android:layout_marginBottom="20dp"
        android:visibility="gone"/>


</android.support.constraint.ConstraintLayout>

标签： javaandroidnullinvoke

解决方案

'btn_reset_password' 按钮的代码已被注释。只需取消注释按钮代码，它应该可以工作。

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