如何在 Android Studio 中使用 RecyclerView 显示数据？

Question

I want to display data using a RecyclerView. but has a problem: "java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference"

and this exception

"java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference"
(ViewActivity.java:45)

this code

   protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_view);

    ButterKnife.bind(this);
    viewAdapter = new RecyclerViewAdapter(this, perusahaan);
    RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
    recyclerView.setLayoutManager(mLayoutManager);
    recyclerView.setItemAnimator(new DefaultItemAnimator());
    recyclerView.setAdapter(viewAdapter);

    LoadDataPerusahaan();
}

Answer 1

这个问题是为了初始化recyclerview ，你可以再次检查ButterKnife以确保正常工作。

Answer 2

I want to display data using a RecyclerView. but has a problem: "java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference"

and this exception

"java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference"
(ViewActivity.java:45)

this code

   protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_view);

    ButterKnife.bind(this);
    viewAdapter = new RecyclerViewAdapter(this, perusahaan);
    RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
    recyclerView.setLayoutManager(mLayoutManager);
    recyclerView.setItemAnimator(new DefaultItemAnimator());
    recyclerView.setAdapter(viewAdapter);

    LoadDataPerusahaan();
}