我试图在RecyclerView中接收带有数组的列表并收到错误:
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
RecyclerView小部件
<android.support.v7.widget.RecyclerView
android:id="@+id/drawerList"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</android.support.v7.widget.RecyclerView>
我尝试将LayoutManager声明为final,但它没有帮助。
活动代码:
public class MainActivity extends ActionBarActivity {
private RecyclerView recyclerView;
private Toolbar toolbar;
private InfAdapter adapter;
@Override
protected void onCreate (Bundle savedInstanceState) {
super.onCreate (savedInstanceState);
setContentView (R.layout.activity_main_appbar);
recyclerView = (RecyclerView) findViewById(R.id.drawerList);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
InfAdapter mAdapter = new InfAdapter(this, getData());
recyclerView.setAdapter(mAdapter);
recyclerView.setItemAnimator(new DefaultItemAnimator());
toolbar = (Toolbar) findViewById(R.id.app_bar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
适配器代码:
public class InfAdapter extends RecyclerView.Adapter<InfAdapter.MyViewHolder> {
private final Context context;
private List<Information> data = Collections.emptyList();
public InfAdapter(Context context, List<Information> data){
this.data = data;
this.context = context;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.custom_row, parent, false);
return new MyViewHolder(v);
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
Information current = data.get(position);
holder.title.setText(current.title);
holder.icon.setImageResource(current.iconid);
}
@Override
public int getItemCount() {
return data.size();
}
class MyViewHolder extends RecyclerView.ViewHolder{
TextView title;
ImageView icon;
public MyViewHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.listText);
icon = (ImageView) itemView.findViewById(R.id.listIcon);
}
}
}
可能出了什么问题?
答案 0 :(得分:23)
正如@StenSoft在评论中指出的那样,问题出在了
setContentView (R.layout.activity_main_appbar);
因为活动布局内容错误而不是
setContentView (R.layout.activity_main);
答案 1 :(得分:7)
在我的情况下出现此错误是因为我没有在我的某个活动中创建RecyclerView
。
检查您的活动布局或片段布局。
答案 2 :(得分:0)
我有类似的东西,但在 kotlin 和里面
RecyclerView.apply {}
代码,在一行中:
layoutManager = viewManager
最终我发现这是因为我将错误的布局膨胀到片段中:
return inflater.inflate(R.layout.main_fragment, container, false)