Java NullPointerException Android-无法启动活动

不太清楚我为什么会出现以下错误，因为代码是从另一个页面中提取的，并且在那里工作正常

01-19 22:38:06.443: E/AndroidRuntime(27945): FATAL EXCEPTION: main
01-19 22:38:06.443: E/AndroidRuntime(27945): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.fooditemmonitor/com.example.fooditemmonitor.CurrentItems}: java.lang.NullPointerException
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.app.ActivityThread.access$700(ActivityThread.java:159)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.os.Looper.loop(Looper.java:176)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.app.ActivityThread.main(ActivityThread.java:5419)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at java.lang.reflect.Method.invokeNative(Native Method)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at java.lang.reflect.Method.invoke(Method.java:525)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at dalvik.system.NativeStart.main(Native Method)
01-19 22:38:06.443: E/AndroidRuntime(27945): Caused by: java.lang.NullPointerException
01-19 22:38:06.443: E/AndroidRuntime(27945):    at com.example.fooditemmonitor.CurrentItems.onCreate(CurrentItems.java:22)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.app.Activity.performCreate(Activity.java:5372)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
01-19 22:38:06.443: E/AndroidRuntime(27945):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
01-19 22:38:06.443: E/AndroidRuntime(27945):    ... 11 more

当前库存.xml

<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/GridLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:columnCount="1" >

    <Button
        android:id="@+id/editItemCurrent"
        android:layout_width="145dp"
        android:layout_column="0"
        android:layout_gravity="right|bottom"
        android:layout_row="0"
        android:text="@string/editItem" />

    <Button
        android:id="@+id/scanCurrent"
        android:layout_width="160dp"
        android:layout_column="0"
        android:layout_gravity="left|bottom"
        android:layout_row="0"
        android:text="@string/scan" />

</GridLayout>

addButton.setOnClickListener（新的OnClickListener（）{//第22行

从文件中发布的代码将与此相关。请检查所引用文件的名称是否正确

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非常感谢您的帮助-谢谢！

我认为您输入了一个错误，应该是：

final Button addButton = (Button) findViewById(R.id.editItemCurrent);
final Button editInventoryButton = (Button) findViewById(R.id.scanCurrent);

---

我在您的布局中未看到id为

scanner

或

editItem

的按钮。

R.id.scanner和R.id.editItem不在当前的\u inventory.xml文件中

---

然后，当您尝试设置OnClickListener in（Button）时，addButton为null并引发NullPointerException。

就是这样，非常感谢！盯着代码看太多让我看不清：（@tagz2712休息一下：）

final Button addButton = (Button) findViewById(R.id.editItemCurrent);
final Button editInventoryButton = (Button) findViewById(R.id.scanCurrent);