Java 除了XML文件外，没有任何更改，并获得以下内容：尝试在空对象引用上调用虚拟方法SetonClickListner

我正在开发的应用程序工作得非常好；我只更改了xml文件设计，当我更改它时，我一直遇到以下问题：

11-19 22:24:13.278 21043-21043/de.nocnoc.clean.cleanlight I/Timeline: Timeline: Activity_launch_request id:de.nocnoc.clean.cleanlight time:12506541
11-19 22:24:13.385 21043-21043/de.nocnoc.clean.cleanlight D/AndroidRuntime: Shutting down VM
11-19 22:24:13.386 21043-21043/de.nocnoc.clean.cleanlight E/AndroidRuntime: FATAL EXCEPTION: main
Process: de.nocnoc.clean.cleanlight, PID: 21043
java.lang.RuntimeException: Unable to start activity ComponentInfo{de.nocnoc.clean.cleanlight/de.nocnoc.clean.flashlight.MaincourseActivity}: 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:2464)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2524)
at android.app.ActivityThread.access$900(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1391)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:234)
at android.app.ActivityThread.main(ActivityThread.java:5526)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at de.nocnoc.clean.flashlight.MaincourseActivity.onCreate(MaincourseActivity.java:163)
at android.app.Activity.performCreate(Activity.java:6285)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2417)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2524)
at android.app.ActivityThread.access$900(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1391)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:234)
at android.app.ActivityThread.main(ActivityThread.java:5526)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

这是我的活动_maincourse.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="de.nocnoc.clean.flashlight.DrinksActivity"
android:background="@android:color/background_light">

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/scrollView">

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true">



        <ImageView
            android:layout_width="80dp"
            android:layout_height="200dp"
            android:src="@drawable/lemon_juice"
            android:id="@+id/item1_image"
            android:layout_alignParentTop="true"
            android:layout_alignParentStart="true" />
        <Button
            android:layout_width="@android:dimen/app_icon_size"
            android:layout_height="wrap_content"
            android:background="#ffff8800"
            android:textColor="@android:color/background_dark"
            android:text="-"
            android:id="@+id/item1minusbtn"
            android:layout_marginStart="25dp"
            android:layout_marginBottom="48dp"
            android:layout_above="@+id/item2_image"
            android:layout_toEndOf="@+id/item1_image"  />

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:backgroundTint="#ffffbb33"
            android:text="0"
            android:id="@+id/item10btn"
            android:layout_alignBottom="@+id/item1minusbtn"
            android:layout_toEndOf="@+id/item1minusbtn"
            android:layout_marginStart="28dp"
            android:background="@android:color/background_light"
            android:autoText="true"
            android:textColor="@android:color/background_dark" />
        <Button
            style="?android:attr/buttonStyleSmall"
            android:background="#ffff8800"
            android:textColor="@android:color/background_dark"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="+"
            android:id="@+id/item1plusbtn"
            android:layout_alignBottom="@+id/item10btn"
            android:layout_toEndOf="@+id/item10btn"
            android:layout_marginStart="32dp" />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Lemon Juice"
            android:textSize="20dp"
            android:id="@+id/item1text"
            android:layout_marginBottom="35dp"
            android:layout_above="@+id/item1minusbtn"
            android:layout_alignStart="@+id/item1minusbtn"
            android:background="@android:color/background_light"
            android:textColor="@android:color/background_dark" />

注意：我确信Java文件中没有问题，因为我没有在那里更改任何内容，也没有向按钮、图像等添加任何内容，。。都是一样的，但设计不同

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求求你，救命

由于您尚未上载Java文件，但可能会发生这些错误

检查已在其上实现click listener exist的视图，并检查该视图的id是否正确

检查xml文件中是否也存在视图id

检查你的打字是否正确，并在适当的视野下进行投射

基本上，这两个是导致空指针异常的最基本解决方案。

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希望这有帮助。

如果您可以附加java代码。点击监听器设置程序有问题，然后你应该发布它。似乎你添加了一个点击监听器到按钮，而这个按钮已经不存在了