Java Android RecyclerView为空

它以前一直在工作，但突然它没有工作，即使我甚至没有更改代码。。。我在我的RecyclerView实例上得到一个空引用，异常告诉我。。。 以下是我的Java代码：

    RecyclerView recyclerView;
    RecyclerView.Adapter rvadapter;
    RecyclerView.LayoutManager rvLayoutManager;

    static ArrayList<String> itemTexte;

    File dir;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recycler_view);
        dir = new File(Environment.getExternalStorageDirectory(), "Notizen");
        if (!dir.exists()) {
            try {
                dir.mkdirs();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        itemTexte = new ArrayList<>();

        recyclerView = (RecyclerView) findViewById(R.id.recyclerview);

        rvLayoutManager = new LinearLayoutManager(RecyclerViewActivity.this);
        recyclerView.setLayoutManager(rvLayoutManager);

        rvadapter = new RvAdapterKlasse(RecyclerViewActivity.this);
        recyclerView.setAdapter(rvadapter);

        notizenSetup();
    }

错误：

04-09 10:35:23.131 15155-15155/at.wurz.david.recyclerviewtemplate D/AndroidRuntime: Shutting down VM
04-09 10:35:23.133 15155-15155/at.wurz.david.recyclerviewtemplate E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                    Process: at.wurz.david.recyclerviewtemplate, PID: 15155
                                                                                    java.lang.RuntimeException: Unable to start activity ComponentInfo{at.wurz.david.recyclerviewtemplate/at.wurz.david.recyclerviewtemplate.RecyclerViewActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
                                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2462)
                                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2524)
                                                                                        at android.app.ActivityThread.access$800(ActivityThread.java:167)
                                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1419)
                                                                                        at android.os.Handler.dispatchMessage(Handler.java:111)
                                                                                        at android.os.Looper.loop(Looper.java:194)
                                                                                        at android.app.ActivityThread.main(ActivityThread.java:5546)
                                                                                        at java.lang.reflect.Method.invoke(Native Method)
                                                                                        at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964)
                                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)
                                                                                     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
                                                                                        at at.wurz.david.recyclerviewtemplate.RecyclerViewActivity.onCreate(RecyclerViewActivity.java:76)
                                                                                        at android.app.Activity.performCreate(Activity.java:5977)
                                                                                        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1111)
                                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2415)
                                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2524) 
                                                                                        at android.app.ActivityThread.access$800(ActivityThread.java:167) 
                                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1419) 
                                                                                        at android.os.Handler.dispatchMessage(Handler.java:111) 
                                                                                        at android.os.Looper.loop(Looper.java:194) 
                                                                                        at android.app.ActivityThread.main(ActivityThread.java:5546) 
                                                                                        at java.lang.reflect.Method.invoke(Native Method) 
                                                                                        at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964) 
                                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759) 

---

我搜索了这个错误，但是所有的主题都至少有一年历史了，并且说谷歌已经修复了这个错误

清理并生成，它应该修复错误并再次尝试添加支持库

错误堆栈跟踪在哪里？编辑！如果你能从中读出一些东西…：DYou已实例化RecyclerView.LayoutManager rvLayoutManager；您的对象找不到RecyclerView，可能是支持库出错。。清理项目并再次尝试添加支持库。听起来不错…：）快乐编码

04-09 10:35:23.131 15155-15155/at.wurz.david.recyclerviewtemplate D/AndroidRuntime: Shutting down VM
04-09 10:35:23.133 15155-15155/at.wurz.david.recyclerviewtemplate E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                    Process: at.wurz.david.recyclerviewtemplate, PID: 15155
                                                                                    java.lang.RuntimeException: Unable to start activity ComponentInfo{at.wurz.david.recyclerviewtemplate/at.wurz.david.recyclerviewtemplate.RecyclerViewActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
                                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2462)
                                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2524)
                                                                                        at android.app.ActivityThread.access$800(ActivityThread.java:167)
                                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1419)
                                                                                        at android.os.Handler.dispatchMessage(Handler.java:111)
                                                                                        at android.os.Looper.loop(Looper.java:194)
                                                                                        at android.app.ActivityThread.main(ActivityThread.java:5546)
                                                                                        at java.lang.reflect.Method.invoke(Native Method)
                                                                                        at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964)
                                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)
                                                                                     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
                                                                                        at at.wurz.david.recyclerviewtemplate.RecyclerViewActivity.onCreate(RecyclerViewActivity.java:76)
                                                                                        at android.app.Activity.performCreate(Activity.java:5977)
                                                                                        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1111)
                                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2415)
                                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2524) 
                                                                                        at android.app.ActivityThread.access$800(ActivityThread.java:167) 
                                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1419) 
                                                                                        at android.os.Handler.dispatchMessage(Handler.java:111) 
                                                                                        at android.os.Looper.loop(Looper.java:194) 
                                                                                        at android.app.ActivityThread.main(ActivityThread.java:5546) 
                                                                                        at java.lang.reflect.Method.invoke(Native Method) 
                                                                                        at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964) 
                                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)