我的应用程序不断地崩溃，说：“我的；“已经停止”；原因：java.lang.NullPointerException

我在调试模式下运行应用程序，然后它继续崩溃。logicat监视器上显示：

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 nws.iceapp.MainActivity.imgButtonLoadPage(MainActivity.java:174)
at nws.iceapp.MainActivity.onCreate(MainActivity.java:160)

下面是我单击时弹出的内容（MainActivity.java:174）

特别是从imgButtonLoadpage开始，当我单击（MainActivity.java:160）时，会弹出：

            imgButtonLoadPage(R.id.asthma, R.layout.act_ast);
            imgButtonLoadPage(R.id.vomiting, R.layout.act_vom);
            imgButtonLoadPage(R.id.unconscious, R.layout.act_unc);
            imgButtonLoadPage(R.id.fracture2, R.layout.act_fra);
            imgButtonLoadPage(R.id.dislocate2, R.layout.act_dis);
            imgButtonLoadPage(R.id.heart_attack2, R.layout.act_hea);

        }

以下是布局xml代码：

<?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="nws.iceapp.MainActivity">

    <ScrollView
        android:id="@+id/scrollView2"
        android:layout_width="368dp"
        android:layout_height="518dp"
        android:layout_marginBottom="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHorizontal_bias="0.506"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:weightSum="1">

            <ImageButton

                android:id="@+id/asthma"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:layout_weight="1.16"
                android:scaleType="centerCrop"
                android:src="@drawable/asthma_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.189"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.11" />

            <TextView
                android:id="@+id/ast"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:text="Asthma"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />


            <ImageButton
                android:id="@+id/vomiting"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:layout_weight="0.47"
                android:scaleType="centerCrop"
                android:src="@drawable/vomit_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.189"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.452" />

            <TextView
                android:id="@+id/vom"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:text="Vomiting"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />

            <ImageButton
                android:id="@+id/unconscious"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:scaleType="centerCrop"
                android:src="@drawable/lost_conscious_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.774"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.11" />

            <TextView
                android:id="@+id/unc"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:text="Unconscious"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />

            <ImageButton
                android:id="@+id/fracture2"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:scaleType="centerCrop"
                android:src="@drawable/fracture_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.189"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.794" />

            <TextView
                android:id="@+id/fra"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Fracture"
                android:gravity="center"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />

            <ImageButton
                android:id="@+id/dislocate2"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:scaleType="centerCrop"
                android:src="@drawable/dislocate_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.774"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.452" />

            <TextView
                android:id="@+id/dis"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Dislocate"
                android:gravity="center"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />

            <ImageButton
                android:id="@+id/heart_attack2"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:scaleType="centerCrop"
                android:src="@drawable/heart_attack_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.774"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.794" />

            <TextView
                android:id="@+id/hea"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Heart Attack"
                android:background="#333"
                android:textColor="#fff"
                android:gravity="center"
                android:textSize="21sp" />


        </LinearLayout>
    </ScrollView>
</android.support.constraint.ConstraintLayout>

这个问题可能是新来者问得最多的问题，Android Studio标签与此无关。如果在Java或Android中出现NullPointerException，则可能没有使用

new

关键字或

findViewById（）

或相关方法实例化视图或对象。简而言之，您的视图没有从xml文件膨胀，内存中有空指针。您应该在打开线程之前进行搜索，尤其是空指针异常线程。

看起来像

imgBtn1

is

null

在

imgButtonLoadPage

调用之前是否调用了

setContentView

？抱歉，我在javacall

setContentView（R.layout.yourlayout）

onCreate

<?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="nws.iceapp.MainActivity">

    <ScrollView
        android:id="@+id/scrollView2"
        android:layout_width="368dp"
        android:layout_height="518dp"
        android:layout_marginBottom="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHorizontal_bias="0.506"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:weightSum="1">

            <ImageButton

                android:id="@+id/asthma"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:layout_weight="1.16"
                android:scaleType="centerCrop"
                android:src="@drawable/asthma_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.189"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.11" />

            <TextView
                android:id="@+id/ast"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:text="Asthma"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />


            <ImageButton
                android:id="@+id/vomiting"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:layout_weight="0.47"
                android:scaleType="centerCrop"
                android:src="@drawable/vomit_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.189"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.452" />

            <TextView
                android:id="@+id/vom"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:text="Vomiting"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />

            <ImageButton
                android:id="@+id/unconscious"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:scaleType="centerCrop"
                android:src="@drawable/lost_conscious_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.774"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.11" />

            <TextView
                android:id="@+id/unc"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:text="Unconscious"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />

            <ImageButton
                android:id="@+id/fracture2"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:scaleType="centerCrop"
                android:src="@drawable/fracture_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.189"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.794" />

            <TextView
                android:id="@+id/fra"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Fracture"
                android:gravity="center"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />

            <ImageButton
                android:id="@+id/dislocate2"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:scaleType="centerCrop"
                android:src="@drawable/dislocate_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.774"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.452" />

            <TextView
                android:id="@+id/dis"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Dislocate"
                android:gravity="center"
                android:background="#333"
                android:textColor="#fff"
                android:textSize="21sp" />

            <ImageButton
                android:id="@+id/heart_attack2"
                android:layout_width="match_parent"
                android:layout_height="115dp"
                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:scaleType="centerCrop"
                android:src="@drawable/heart_attack_icon"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.774"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.794" />

            <TextView
                android:id="@+id/hea"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Heart Attack"
                android:background="#333"
                android:textColor="#fff"
                android:gravity="center"
                android:textSize="21sp" />


        </LinearLayout>
    </ScrollView>
</android.support.constraint.ConstraintLayout>