使RecyclerView中的项目可单击时出现问题

我知道有这样的问题，但我的问题无法解决。

我正在尝试将'RecyclerView'设置为'OnItemClicklistener'，但是当我运行该应用程序时，它将停止。.

你能告诉我错误在哪里吗？

以下是代码：（请注意，错误在于使该项目可点击）

这是“ RecyclerView”的“适配器”：

public class Teacheractivity extends AppCompatactivity {
private FirebaseAuth mAuth=FirebaseAuth.getInstance();
private FirebaseUser currentUser= mAuth.getcurrentUser();;
private FirebaseFirestore db = FirebaseFirestore.getInstance();
private String UserId =currentUser.getUid();
private static String city;
private TeacherAdapter teacherAdapter;
public static final String EXTRA_PATH = "com.example.exercise.EXTRA_PATH";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_teacher);
setUpRecyclerView();
teacherAdapter.setOnItemClicklistener(new TeacherAdapter.OnItemClicklistener() {
@Override
public void onItemClick(Documentsnapshot documentsnapshot,int position) {
String path = documentsnapshot.getReference().getPath();
Intent intent = new Intent(Teacheractivity.this,Secondactivity.class);
intent.putExtra(EXTRA_PATH,path);
startactivity(intent);
}
});
}// end of onCreate
private void setUpRecyclerView(){
Query query = db.collection("Teachers");
FirestoreRecyclerOptions optiOns= new
FirestoreRecyclerOptions.Builder()
.setQuery(query,Teacher.class)
.build();
teacherAdapter = new TeacherAdapter(options);
RecyclerView recyclerView = findViewById(R.id.recycler_view);
recyclerView.setHasFixedSize(true); //for performane reasons
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setadapter(teacherAdapter);
teacherAdapter.startListening();
}
@Override
protected void onStart() {
super.onStart();
}
@Override
protected void onStop() {
super.onStop();
teacherAdapter.stopListening();
}
}// end of class


logcat的一部分：

  

E / Android运行时：致命异常：主要
      进程：com.example.exercise，PID：29966
      java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.exercise / com.example.exercise.Teacheractivity}：java.lang.NullPointerException：尝试调用虚拟方法'void com.example.exercise.TeacherAdapter.setOnItemClicklistener（ com.example.exercise.TeacherAdapter $ OnItemClicklistener）”上的空对象引用

您遇到以下错误：

  

E / AndroidRuntime：致命例外：主进程：com.example.exercise，PID：29966 java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.exercise / com.example.exercise.TeacherActivity}：java .lang.NullPointerException：尝试在空对象引用上调用虚拟方法'void com.example.exercise.TeacherAdapter.setOnItemClickListener（com.example.exercise.TeacherAdapter $ OnItemClickListener）'

因为此时您正在对.setOnItemClickListener()的{​​{1}}对象调用teacherAdapter。要解决此问题，您只需移动以下代码块：

null

在适配器声明之后：

teacherAdapter.setOnItemClickListener(new TeacherAdapter.OnItemClickListener() {
@Override
public void onItemClick(DocumentSnapshot documentSnapshot,int position) {
String path = documentSnapshot.getReference().getPath();
Intent intent = new Intent(TeacherActivity.this,SecondActivity.class);
intent.putExtra(EXTRA_PATH,path);
startActivity(intent);
}
});


使用您的teacherAdapter = new TeacherAdapter(options);
方法，您的问题将得到解决。