android - 为什么 RecycleView 让我的应用程序在 Fragments 中崩溃？
问题描述
我对 RecyclerView 不太熟悉，所以请多多包涵，因为我不是 Android 专家。这里的问题是，当我从 NavDrawer 中单击菜单时，我的应用程序将崩溃。
我已经搜索过，但找不到一些运气。我已经在另一个项目中使用了相同的代码，该项目只显示了回收器视图，并且除了这个之外它都可以工作。
有人可以检查出了什么问题吗？
日志猫
2019-07-07 11:21:00.464 7321-7321/com.example.devcash E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.devcash, PID: 7321
android.view.InflateException: Binary XML file line #10: Binary XML file line #10: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #10: Error inflating class fragment
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
at com.example.devcash.Fragments.InventoryListFragment.initRecyclerView(InventoryListFragment.java:96)
at com.example.devcash.Fragments.InventoryListFragment.initImageBitmaps(InventoryListFragment.java:90)
at com.example.devcash.Fragments.InventoryListFragment.onCreateView(InventoryListFragment.java:64)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2439)
at android.support.v4.app.FragmentManagerImpl.ensureInflatedFragmentView(FragmentManager.java:1689)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1431)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1684)
at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1930)
at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:3745)
at android.view.LayoutInflater$FactoryMerger.onCreateView(LayoutInflater.java:190)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:776)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:734)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:865)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:828)
at android.view.LayoutInflater.inflate(LayoutInflater.java:525)
at android.view.LayoutInflater.inflate(LayoutInflater.java:427)
at com.example.devcash.Fragments.InventoryFragment.onCreateView(InventoryFragment.java:31)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2439)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1460)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:802)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:733)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6823)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1563)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1451)
InventoryListFragment.java
public class InventoryListFragment extends Fragment implements InventoryRecyclerViewAdapter.onInventoryListener{
private static final String TAG = "InventoryListFragment";
//variables
private ArrayList<Integer> mIcon = new ArrayList<>();
private ArrayList<String> mLabel = new ArrayList<>();
public InventoryListFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_inventory_list, container, false);
RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.inventorylist_recycleview);
recyclerView.addItemDecoration(new HorizontalDividerItemDecoration.Builder(getActivity())
.build()); //adding a divider into the recyclerview list
Log.d(TAG, "onCreateView: started");
initImageBitmaps();
return view;
}
private void initImageBitmaps(){
Log.d(TAG, "initImageBitmaps: preparing bitmaps");
mIcon.add(R.drawable.ic_product);
mLabel.add("Products");
mIcon.add(R.drawable.ic_customer);
mLabel.add("Services");
mIcon.add(R.drawable.ic_category);
mLabel.add("Categories");
mIcon.add(R.drawable.ic_tag);
mLabel.add("Discounts");
initRecyclerView();
}
private void initRecyclerView(){
// Log.d(TAG, "initRecyclerView: init recyclerview");
RecyclerView recyclerView = getView().findViewById(R.id.inventorylist_recycleview);
InventoryRecyclerViewAdapter adapter = new InventoryRecyclerViewAdapter(getActivity(), mIcon, mLabel);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
}
//method created from OnInventoryListener from InventoryListFragment.java
//handles the onclick for the recycleview items
@Override
public void onInventoryClick(int position) {
mLabel.get(position); //get the position of the clicked item
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
switch (position){
case 0:
ProductsFragment productsFragment = new ProductsFragment();
fragmentTransaction.replace(R.id.inventorylist_fragmentcontainer, productsFragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
break;
case 1:
ServicesFragment servicesFragment = new ServicesFragment();
fragmentTransaction.replace(R.id.inventorylist_fragmentcontainer, servicesFragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
break;
case 2:
CategoriesFragment categoriesFragment = new CategoriesFragment();
fragmentTransaction.replace(R.id.inventorylist_fragmentcontainer, categoriesFragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
break;
case 3:
DiscountsFragment discountsFragment = new DiscountsFragment();
fragmentTransaction.replace(R.id.inventorylist_fragmentcontainer, discountsFragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
break;
}
}
InventoryRecyclerViewAdapter.java
public class InventoryRecyclerViewAdapter extends RecyclerView.Adapter<InventoryRecyclerViewAdapter.ViewHolder>{
private static final String TAG = "RecyclerViewAdapter";
private ArrayList<Integer> mIcon = new ArrayList<>();
private ArrayList<String> mLabel = new ArrayList<>();
private Context context;
public InventoryRecyclerViewAdapter(Context context, ArrayList<Integer> mIcon, ArrayList<String> mLabel) {
this.mIcon = mIcon;
this.mLabel = mLabel;
this.context = context;
}
//responsible for inflating the view
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.customlayout_inventorylist, viewGroup, false);
ViewHolder holder = new ViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(@NonNull InventoryRecyclerViewAdapter.ViewHolder viewHolder, final int i) {
Log.d(TAG, "onBindViewHolder: called.");
Glide.with(context)
.asBitmap()
.load(mIcon.get(i))
.into(viewHolder.icon);
viewHolder.label.setText(mLabel.get(i));
viewHolder.customLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "OnClick: clicked on: " + mLabel.get(i));
Toast.makeText(context, mLabel.get(i), Toast.LENGTH_SHORT).show();
}
});
}
@Override
public int getItemCount() {
return mLabel.size();
}
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
ImageView icon;
TextView label;
LinearLayout customLayout;
public ViewHolder(@NonNull View itemView) {
super(itemView);
icon = itemView.findViewById(R.id.inventorylist_icon);
label = itemView.findViewById(R.id.inventorylist_title);
customLayout = itemView.findViewById(R.id.inventoryoptions_layout);
itemView.setOnClickListener(this);
}
@Override
public void onClick(View v) {
}
}
public interface onInventoryListener{
void onInventoryClick(int position);
}
解决方案
传递您膨胀的视图变量并findViewById在其上使用，而不是使用getView() .
getView()如果在返回视图之前调用它，则返回 null onCreateView()。（参考）
更新：
initImageBitmaps方法一：调用onViewCreated
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
initImageBitmaps();
}
方法二：函数间传递视图变量
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_inventory_list, container, false);
RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.inventorylist_recycleview);
recyclerView.addItemDecoration(new HorizontalDividerItemDecoration.Builder(getActivity())
.build()); //adding a divider into the recyclerview list
Log.d(TAG, "onCreateView: started");
initImageBitmaps(view);
return view;
}
private void initImageBitmaps(View view){
Log.d(TAG, "initImageBitmaps: preparing bitmaps");
mIcon.add(R.drawable.ic_product);
mLabel.add("Products");
mIcon.add(R.drawable.ic_customer);
mLabel.add("Services");
mIcon.add(R.drawable.ic_category);
mLabel.add("Categories");
mIcon.add(R.drawable.ic_tag);
mLabel.add("Discounts");
initRecyclerView(view);
}
private void initRecyclerView(View view){
// Log.d(TAG, "initRecyclerView: init recyclerview");
RecyclerView recyclerView = view.findViewById(R.id.inventorylist_recycleview);
InventoryRecyclerViewAdapter adapter = new InventoryRecyclerViewAdapter(getActivity(), mIcon, mLabel);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
}
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