I am trying to construct an app where I have fragments. Inside these fragments, I am using a RecyclerView. Also, there is a CardView widget for a Customer
entity class under my layouts directory, called card_view_customer.xml
. But, when I create an instance for my current adapter under the CustomerFragment.java
class, app is crushing due to some reason I don't know. I believe the problem is that my adapter is implemented wrongly, but I don't know how to fix it. These are the codes currently;
onCreateView()
function under CustomerFragment.java
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_customer, container, false);
// Inflate the layout for this fragment
RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
final SalesTrackerAdapter adapter = new SalesTrackerAdapter(getActivity());
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
mSalesTrackerViewModel = new ViewModelProvider(getActivity()).get(SalesTrackerViewModel.class);
mSalesTrackerViewModel.getAllCustomers().observe(getActivity(), new Observer<List<Customer>>() {
@Override
public void onChanged(List<Customer> customers) {
adapter.setCustomers(customers);
}
});
return view;
}
card_view_customer.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp"
android:background="#00D8D8">
<androidx.cardview.widget.CardView
android:id="@+id/card_view_customer"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:cardCornerRadius="4dp"
app:contentPadding="10dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/customerTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
style="@style/customer_title"
android:layout_alignParentStart="true" />
</RelativeLayout>
</androidx.cardview.widget.CardView>
fragment_customer.xml
where I use RecyclerView
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".CustomerFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0" />
</FrameLayout>
And the problem is most likely in this code where I have tried to implement the adapter, but crashes when I used it under onCreateView()
function in CustomerFragment.java
SalesTrackerAdapter
public class SalesTrackerAdapter extends RecyclerView.Adapter<SalesTrackerAdapter.SalesTrackerViewHolder> {
class SalesTrackerViewHolder extends RecyclerView.ViewHolder{
private final TextView customerTitle;
private SalesTrackerViewHolder(View itemView){
super(itemView);
customerTitle = itemView.findViewById(R.id.customerTitle);
}
}
private final LayoutInflater myInflater;
private List<Customer> myCustomers;
SalesTrackerAdapter(Context context){myInflater = LayoutInflater.from(context);}
@Override
public SalesTrackerViewHolder onCreateViewHolder(ViewGroup parent, int viewType){
View itemView = myInflater.inflate(R.layout.card_view_customer, parent, false);
return new SalesTrackerViewHolder(itemView);
}
@Override
public void onBindViewHolder(SalesTrackerViewHolder holder, int position){
if (myCustomers != null) {
Customer current = myCustomers.get(position);
holder.customerTitle.setText(current.getName());
} else {
holder.customerTitle.setText("No Customers");
}
}
void setCustomers(List<Customer> customers){
myCustomers = customers;
notifyDataSetChanged();
}
@Override
public int getItemCount(){
if(myCustomers != null){
return myCustomers.size();
}
return 0;
}
}
I believe something is wrong in this adapter, becaues whenever it is referred in onCreateView()
emulator says that the app "keeps stopping". When I commented out those lines, it works fine so far. What I want is to fetch customers from the database, which I ve done by implementing repository and viewmodel classes and display them inside the cardviews under the fragment. These are the codes for my repository and ViewModel:
public class SalesTrackerRepository {
//Dao instances.
private CustomerDao mCustomerDao;
//Listing items.
private LiveData<List<Customer>> mAllCustomers;
SalesTrackerRepository(Application application){
SalesTrackerDatabase db = SalesTrackerDatabase.getDatabase(application);
mCustomerDao = db.customerDao();
mAllCustomers = mCustomerDao.getCustomers();
}
LiveData<List<Customer>> getAllCustomers(){
return mAllCustomers;
}
void insert(Customer customer){
SalesTrackerDatabase.databaseWriteExecutor.execute(() -> mCustomerDao.insert(customer));
}
}
ViewModel
public class SalesTrackerViewModel extends AndroidViewModel {
private SalesTrackerRepository mRepository;
private LiveData<List<Customer>> mAllCustomers;
private SalesTrackerViewModel(Application application){
super(application);
mRepository = new SalesTrackerRepository(application);
mAllCustomers = mRepository.getAllCustomers();
}
LiveData<List<Customer>> getAllCustomers(){return mAllCustomers;}
public void insert(Customer customer){mRepository.insert(customer);}
}
I have just started to android and trying to learn with this project. Sorry for if there are any meaningless points in the question. Thanks in advance.
Edit: The problem might be in the ViewModel class as well. I think crash occurs due to following block:
mSalesTrackerViewModel = new ViewModelProvider(getActivity()).get(SalesTrackerViewModel.class);
mSalesTrackerViewModel.getAllCustomers().observe(getActivity(), new Observer<List<Customer>>() {
@Override
public void onChanged(List<Customer> customers) {
adapter.setCustomers(customers);
}
});
Edit 2: Here is my logcat
2020-04-19 23:17:09.786 11114-11114/com.example.salestrackertest3 E/lestrackertest: Unknown bits set in runtime_flags: 0x8000
2020-04-19 23:17:12.011 11114-11114/com.example.salestrackertest3 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.salestrackertest3, PID: 11114
java.lang.RuntimeException: Cannot create an instance of class com.example.salestrackertest3.SalesTrackerViewModel
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:269)
at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
at com.example.salestrackertest3.CustomerFragment.onCreateView(CustomerFragment.java:90)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2698)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:310)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1185)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1354)
at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1432)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1495)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:447)
at androidx.fragment.app.FragmentManager.executeOps(FragmentManager.java:2167)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1990)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1945)
at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1816)
at androidx.fragment.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:303)
at androidx.fragment.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:238)
at androidx.viewpager.widget.ViewPager.populate(ViewPager.java:1244)
at androidx.viewpager.widget.ViewPager.populate(ViewPager.java:1092)
at androidx.viewpager.widget.ViewPager.onMeasure(ViewPager.java:1622)
at android.view.View.measure(View.java:24530)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
at androidx.coordinatorlayout.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:760)
at com.google.android.material.appbar.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:99)
at com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1892)
at androidx.coordinatorlayout.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:831)
at android.view.View.measure(View.java:24530)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at androidx.appcompat.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:143)
at android.view.View.measure(View.java:24530)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:842)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:721)
at android.view.View.measure(View.java:24530)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.view.View.measure(View.java:24530)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:842)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:721)
at android.view.View.measure(View.java:24530)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at com.android.internal.policy.DecorView.onMeasure(DecorView.java:742)
at android.view.View.measure(View.java:24530)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:3006)
2020-04-19 23:17:12.012 11114-11114/com.example.salestrackertest3 E/AndroidRuntime: at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1833)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2122)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1721)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7598)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:966)
at android.view.Choreographer.doCallbacks(Choreographer.java:790)
at android.view.Choreographer.doFrame(Choreographer.java:725)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:951)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Caused by: java.lang.NoSuchMethodException: com.example.salestrackertest3.SalesTrackerViewModel.<init> [class android.app.Application]
at java.lang.Class.getConstructor0(Class.java:2332)
at java.lang.Class.getConstructor(Class.java:1728)
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:267)
... 64 more
The following part of the crash log indicates that the runtime can't find a constructor for your ViewModel
Caused by: java.lang.NoSuchMethodException: com.example.salestrackertest3.SalesTrackerViewModel.<init> [class android.app.Application] at java.lang.Class.getConstructor0(Class.java:2332) at java.lang.Class.getConstructor(Class.java:1728) at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:267)
... and as a matter of fact the constructor exists but it is private
:
private SalesTrackerViewModel(Application application){
super(application);
mRepository = new SalesTrackerRepository(application);
mAllCustomers = mRepository.getAllCustomers();
}
So the solution is to make the constructor public
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