java - 应用程序在切换 Activity 时崩溃，构建已完成，没有错误

Question

我的应用程序在从登录后 Activity 切换到应用程序内的个人资料 Activity 时崩溃。构建已完成，没有错误。

有什么想法吗？ (感谢每一个帮助)

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////个人资料 Activity ---->

package com.smarthelp.smarthelp;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;

import com.google.firebase.auth.FirebaseAuth;

public class ProfileActivity extends AppCompatActivity {

    private FirebaseAuth firebaseAuth;
    private Button logout;

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

    firebaseAuth= FirebaseAuth.getInstance();

    logout = (Button)findViewById(R.id.btnLogout);

    logout.setOnClickListener(new View.OnClickListener() {
        @Override
            public void onClick(View v) {
                Logout();
            }
        });

        configureibtnHelp();

    }


    private void Logout(){
        firebaseAuth.signOut();
        finish();
        startActivity(new Intent(ProfileActivity.this, LoginActivity.class));

    }
    private void configureibtnHelp() {
        ImageButton ibtnHelp = (ImageButton) findViewById(R.id.ibtnHelp);
        ibtnHelp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                finish();
            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.profile_menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch(item.getItemId()){
            case R.id.logoutMenu:{
                Logout();

            }
        }
        return super.onOptionsItemSelected(item);
    }


}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////帮助 Activity ---->

package com.smarthelp.smarthelp;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;

import com.google.firebase.auth.FirebaseAuth;

public class HelpActivity extends AppCompatActivity {

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


        configureibtnProfile();
    }

    private void configureibtnProfile(){
        ImageButton ibtnProfile = (ImageButton) findViewById(R.id.ibtnProfile);
        ibtnProfile.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(HelpActivity.this, ProfileActivity.class));
            }
        });
    }

}

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////Activity_help.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=".HelpActivity">

    <ImageButton
        android:id="@+id/ibtnProfile"
        android:layout_width="51dp"
        android:layout_height="52dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:contentDescription="ProfilButton"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.025"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.983"
        app:srcCompat="@drawable/profil" />

    <ImageButton
        android:id="@+id/ibtnOrder"
        android:layout_width="52dp"
        android:layout_height="52dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:contentDescription="OrderButton"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.983"
        app:srcCompat="@drawable/order" />

    <ImageButton
        android:id="@+id/ibtnHelp"
        android:layout_width="51dp"
        android:layout_height="53dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="236dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="236dp"
        android:layout_marginTop="8dp"
        android:contentDescription="HelpButton"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.875"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.983"
        app:srcCompat="@drawable/help" />
</android.support.constraint.ConstraintLayout>

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////------->Logcat

08-13 19:13:15.273 21068-21068/com.smarthelp.smarthelp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.smarthelp.smarthelp, PID: 21068
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.smarthelp.smarthelp/com.smarthelp.smarthelp.ProfileActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at com.smarthelp.smarthelp.ProfileActivity.configureibtnHelp(ProfileActivity.java:48)
        at com.smarthelp.smarthelp.ProfileActivity.onCreate(ProfileActivity.java:35)
        at android.app.Activity.performCreate(Activity.java:7136)
        at android.app.Activity.performCreate(Activity.java:7127)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.app.ActivityThread.main(ActivityThread.java:6669) 

Answer 1

从崩溃日志来看

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

您尝试为其设置 onclick 监听器的按钮上有一个 NPE。在您的 ProfileActivity 中将按钮设置为 XML 的 ImageButtons 之一假设您正在尝试对第一个图像按钮执行操作

只需在设置 onClickListener 之前添加以下行

logout=(Button) findViewById(R.id.ibtnProfile);