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java - 声明 RecyclerView 时出现 NullPointerException

问题描述

我正在尝试在我的项目的活动中声明一个 RecyclerView。当我切换到这个活动时，项目崩溃了。当我尝试实例化我的 RecyclerView 时收到 NullPointerException，请参阅下面的错误：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.marykate.marykatefordefyp, PID: 13490
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.marykate.marykatefordefyp/com.example.marykate.marykatefordefyp.ViewFavourites}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2264)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2313)
        at android.app.ActivityThread.access$1100(ActivityThread.java:141)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1238)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5336)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:681)
        at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
        at com.example.marykate.marykatefordefyp.ViewFavourites.onCreate(ViewFavourites.java:54)
        at android.app.Activity.performCreate(Activity.java:5302)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1090)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2228

我在这个网站上查看过类似的问题，但没有一个答案是我想要的。我没有引用错误的 xml 文件，而是调用了正确的 RecyclerView。请参阅下面的代码：

 RecyclerView eventsListview;
List<Favourite> favourites = new ArrayList<>();
    FaveAdapter adapter = new FaveAdapter(this, R.layout.eventlist_layout, favourites);

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

        eventsListview.findViewById(R.id.eventsListview1); //the line causing an error

有谁知道这可能是什么原因造成的？

标签： javaandroidnullpointerexception

解决方案

eventsListview = (RecyclerView)findViewById(R.id.eventsListview1);

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