Java 将适配器设置为回收器视图时出现空指针异常
无法成功呈现回收器视图。获取错误: “java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget.RecyclerView$Adapter)'” 即使我已经初始化了Java 将适配器设置为回收器视图时出现空指针异常,java,android,firebase,firebase-realtime-database,android-recyclerview,Java,Android,Firebase,Firebase Realtime Database,Android Recyclerview,无法成功呈现回收器视图。获取错误: “java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget.RecyclerView$Adapter)'” 即使我已经初始化了RecyclerView,也要设置线性布局并将其设置为适配器。有人能指出错误吗 @Override protected void onCre
RecyclerView
,也要设置线性布局并将其设置为适配器。有人能指出错误吗
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_food_list);
toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
searchBar = (MaterialSearchBar) findViewById(R.id.searchBar);
if(getIntent() != null ){
if(getIntent().getStringExtra("categoryId") != null){
categoryId = getIntent().getStringExtra("categoryId");
fetchFoodList(categoryId);
}
}
databaseReference = FirebaseDatabase.getInstance().getReference("foodlist");
floatingActionButton = findViewById(R.id.food_list_fab);
recyclerView = findViewById(R.id.food_recycler_view);
final LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
}
private void fetchFoodList(String categoryId) {
Query query = FirebaseDatabase.getInstance().getReference("foodlist").orderByChild("MenuId").equalTo(categoryId);
FirebaseRecyclerOptions<FoodModel> options = new FirebaseRecyclerOptions.Builder<FoodModel>().setQuery(query, new SnapshotParser<FoodModel>() {
@NonNull
@Override
public FoodModel parseSnapshot(@NonNull DataSnapshot snapshot) {
Log.d(TAG, "parseSnapshot: "+snapshot.child("Discount").getValue().toString());
return new FoodModel(snapshot.child("Description").getValue().toString(), snapshot.child("Discount").getValue().toString(), snapshot.child("Image").getValue().toString(), snapshot.child("MenuId").getValue().toString(), snapshot.child("Name").getValue().toString(), snapshot.child("Price").getValue().toString());
}
}).build();
FirebaseRecyclerAdapter firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<FoodModel, FoodViewHolder>(options) {
@NonNull
@Override
public FoodViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
LayoutInflater inflater = LayoutInflater.from(viewGroup.getContext());
View v = inflater.inflate(R.layout.food_items, viewGroup, false);
return new FoodViewHolder(v);
}
@Override
protected void onBindViewHolder(@NonNull FoodViewHolder holder, final int position, @NonNull FoodModel model) {
holder.setFoodName(model.getName());
Log.d(TAG, "onBindViewHolder: "+model.getImage());
holder.setFoodImage(model.getImage());
holder.setFoodDescription(model.getDescription());
}
};
recyclerView.setAdapter(firebaseRecyclerAdapter);
}
@覆盖
创建时受保护的void(@Nullable Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity\u food\u list);
toolbar=findviewbyd(R.id.toolbar);
设置支持操作栏(工具栏);
searchBar=(MaterialSearchBar)findViewById(R.id.searchBar);
如果(getIntent()!=null){
如果(getIntent().getStringExtra(“categoryId”)!=null){
categoryId=getIntent().getStringExtra(“categoryId”);
fetchFoodList(categoryId);
}
}
databaseReference=FirebaseDatabase.getInstance().getReference(“foodlist”);
floatingActionButton=findViewById(R.id.food\u list\u fab);
recyclerView=findViewById(R.id.food\u Recyclers\u视图);
最终LinearLayoutManager layoutManager=新的LinearLayoutManager(本);
recyclerView.setLayoutManager(layoutManager);
}
私有void fetchFoodList(字符串类别ID){
Query Query=FirebaseDatabase.getInstance().getReference(“foodlist”).orderByChild(“MenuId”).equalTo(categoryId);
FirebaseRecyclerOptions选项=新建FirebaseRecyclerOptions.Builder().setQuery(查询,新建快照解析器(){
@非空
@凌驾
public FoodModel parseSnapshot(@NonNull DataSnapshot snapshot){
Log.d(标记“parseSnapshot:+snapshot.child(“折扣”).getValue().toString());
返回新的FoodModel(snapshot.child(“Description”).getValue().toString(),snapshot.child(“折扣”).getValue().toString(),snapshot.child(“Image”).getValue().toString(),snapshot.child(“MenuId”).getValue().toString(),snapshot.child(“Price”).getValue().toString();
}
}).build();
FirebaseRecyclerAdapter FirebaseRecyclerAdapter=新的FirebaseRecyclerAdapter(选项){
@非空
@凌驾
public FoodViewHolder onCreateViewHolder(@NonNull ViewGroup ViewGroup,int i){
LayoutInflater充气器=LayoutInflater.from(viewGroup.getContext());
视图v=充气机。充气(R.layout.food_items,视图组,false);
返回新的FoodViewWolder(v);
}
@凌驾
受保护的无效onBindViewHolder(@NonNull FoodViewHolder,最终int位置,@NonNull FoodModel模型){
setFoodName(model.getName());
d(标记“onBindViewHolder:”+model.getImage());
setFoodImage(model.getImage());
setFoodDescription(model.getDescription());
}
};
recyclerView.setAdapter(firebaseRecyclerAdapter);
}
要解决此问题,请移动以下代码行:
recyclerView = findViewById(R.id.food_recycler_view);
就在这一行之后:
searchBar = (MaterialSearchBar) findViewById(R.id.searchBar);.
通过这种方式,
RecyclerView
对象将在使用它之前初始化。我太傻了。..thnx buddy:)