我想从片段2中的editTexts中输入内容，为片段1中的recyclerview添加项目，然后单击fab以添加包含我在片段2中输入的详细信息的项目。问题是当我调试mExampleAdapter /适配器为null以及mExampleList，我不知道为什么
这是片段1 JAVA代码
package com.example.admin.test2;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
import java.util.ArrayList;
/**
* A simple {@link Fragment} subclass.
*/
public class MainScreen extends Fragment {
private ArrayList <ExampleItem> mExampleList;
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
public MainScreen() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_main_screen, container, false);
DataHandlers dataHandlers = new DataHandlers();
try {
String deTails = dataHandlers.getDetails();
int aMount = dataHandlers.getAmount();
Toast.makeText(getActivity().getApplicationContext(), deTails + "" + aMount, Toast.LENGTH_LONG).show();
//TAS DITO KA NA MAG SET TEXT SA MGA TEXTVIEW NG AMOUNT AT DETAILS
} catch (Exception ex) {
Toast.makeText(getActivity().getApplicationContext(), ex.getMessage().toString(), Toast.LENGTH_LONG).show();
}
mRecyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
mExampleList = new ArrayList <>();
// mExampleList.add(new ExampleItem(R.drawable.ic_library_add_black_24dp, "", "", "ADD EXPENSES"));
mRecyclerView = view.findViewById(R.id.recyclerView);
mRecyclerView.setHasFixedSize(true);
mLayoutManager = new LinearLayoutManager(getContext());
mAdapter = new ExampleAdapter(mExampleList);
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.setAdapter(mAdapter);
return view;
}
public void insertItem() {
// String amount = String.valueOf(amountt.getText());
// String details = String.valueOf((detailss.getText()));
// String date = String.valueOf((datee.getText()));
/*
Bundle bundle = getArguments();
String deTails = bundle.getString("Details");
String aMount = bundle.getString("Amount");
*/
//int position = bundle.getInt("Position");
DataHandlers dataHandlers = new DataHandlers();
String deTails = dataHandlers.getDetails();
int aMount = dataHandlers.getAmount();
mExampleList.add(0, new ExampleItem(R.drawable.food, "Food & Drink", "" + deTails, "₱ " + aMount));
mAdapter.notifyDataSetChanged();
}
}
这是来自2个JAVA代码的片段
package com.example.admin.test2;
import android.app.DatePickerDialog;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Context;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
public class Expense extends Fragment {
public Expense() {
// Required empty public constructor
}
//SPINNER
Spinner sp1;
CustomAdapter adapter;
String[] names = {"Food & Drink", "Shopping", "Transportation", "Home", "Bills & Fees", "Entertainment", "Healthcare", "Education", "Beauty", "Others"};
int[] images = {R.drawable.food, R.drawable.shopping, R.drawable.transportation, R.drawable.home, R.drawable.bills, R.drawable.entertainment, R.drawable.medical, R.drawable.education, R.drawable.beauty, R.drawable.others};
//DATE PICKER
private EditText mDisplayDate;
private DatePickerDialog.OnDateSetListener mDateSetListener;
//FOR THE ADD ITEM
FloatingActionButton fab;
private ArrayList<ExampleItem> mExampleList;
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
EditText amount;
EditText detail;
@Override
public View onCreateView(final LayoutInflater inflater, final ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate (R.layout.fragment_expense, container, false);
//spinner
sp1 = (Spinner)view.findViewById(R.id.customSpinner);
adapter = new CustomAdapter(getActivity(), names, images);
sp1.setAdapter(adapter);
//fab onClick - sending values to the recycler view
fab = (FloatingActionButton) view.findViewById(R.id.fabs);
amount = (EditText) view.findViewById(R.id.textAmountt);
detail = (EditText) view.findViewById(R.id.textDetailss);
final DataHandlers dataHandlers = new DataHandlers();
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// String amountValue = amount.getText().toString();
// String detailValue = detail.getText().toString();
// mExampleList.add(0, new ExampleItem(R.drawable.entertainment, "Entertainment", detailValue, "₱ " + amountValue));
// mAdapter.notifyDataSetChanged();
dataHandlers.setAmount(Integer.parseInt(amount.getText().toString()));
dataHandlers.setDetails(detail.getText().toString());
Toast.makeText(getActivity().getApplicationContext(), dataHandlers.getDetails() + dataHandlers.getAmount(), Toast.LENGTH_LONG).show();
android.support.v4.app.FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
android.support.v4.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
MainScreen ms = new MainScreen();
ms.insertItem();
fragmentTransaction.replace(R.id.replaceLayout, ms);
fragmentTransaction.commit();
}
});
int pos = sp1.getSelectedItemPosition();
//date picker
mDisplayDate = (EditText) view.findViewById(R.id.datePick);
mDisplayDate.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
Calendar cal = Calendar.getInstance();
int year = cal.get(Calendar.YEAR);
int month = cal.get(Calendar.MONTH);
int day = cal.get(Calendar.DAY_OF_MONTH);
DatePickerDialog dialog = new DatePickerDialog(getActivity(),
android.R.style.Theme_Holo_Light_Dialog_MinWidth,
mDateSetListener,
year, month, day);
dialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
dialog.show();
}
});
mDateSetListener = new DatePickerDialog.OnDateSetListener() {
@Override
public void onDateSet(DatePicker view, int year, int month, int day) {
//Calendar calendar = Calendar.getInstance();
//String currentDate = DateFormat.getDateInstance().format(calendar.getTime());
month = month + 1;
String date = month + "-" + day + "-" + year;
mDisplayDate.setText(date);
}
};
return view;
}
}
这是适配器的Java代码
package com.example.admin.test2;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
public class ExampleAdapter extends RecyclerView.Adapter<ExampleAdapter.ExampleViewHolder> {
private ArrayList<ExampleItem> mExampleList;
public static class ExampleViewHolder extends RecyclerView.ViewHolder
{
public ImageView mImageView;
public TextView mLabel;
public TextView mDetails;
public TextView mAmount;
public ExampleViewHolder(View itemView) {
super(itemView);
mImageView = itemView.findViewById(R.id.imageIcon);
mLabel = itemView.findViewById(R.id.textLabel);
mDetails = itemView.findViewById(R.id.textDetails);
mAmount = itemView.findViewById(R.id.textAmount);
}
}
public ExampleAdapter(ArrayList<ExampleItem> exampleList)
{
mExampleList = exampleList;
}
@NonNull
@Override
public ExampleViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.customlist, parent, false);
ExampleViewHolder evh = new ExampleViewHolder(view);
return evh;
}
@Override
public void onBindViewHolder(@NonNull ExampleViewHolder holder, int position) {
ExampleItem currentItem = mExampleList.get(position);
holder.mImageView.setImageResource(currentItem.getmImageResource());
holder.mLabel.setText(currentItem.getMlabel());
holder.mDetails.setText(currentItem.getMdetails());
holder.mAmount.setText(currentItem.getMamount());
}
@Override
public int getItemCount() {
if (mExampleList == null)
return 0;
else
return mExampleList.size();
}
}
这是项目的获取器和设置器
package com.example.admin.test2;
public class ExampleItem {
private int mImageResource;
private String mlabel;
private String mdetails;
private String mamount;
public ExampleItem(int imageResource, String label, String details, String amount)
{
mImageResource = imageResource;
mlabel = label;
mdetails = details;
mamount = amount;
}
public int getmImageResource()
{
return mImageResource;
}
public String getMlabel() {
return mlabel;
}
public String getMdetails() {
return mdetails;
}
public String getMamount() {
return mamount;
}
}
这就是错误
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.admin.test2, PID: 30713
java.lang.NullPointerException: Attempt to invoke virtual method 'void java.util.ArrayList.add(int, java.lang.Object)' on a null object reference
at com.example.admin.test2.MainScreen.insertItem(MainScreen.java:82)
at com.example.admin.test2.Expense$1.onClick(Expense.java:101)
at android.view.View.performClick(View.java:6897)
at android.view.View$PerformClick.run(View.java:26101)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
根据调试mExampleList和mAdapter为null。
mExampleList.add(0, new ExampleItem(R.drawable.food, "Food & Drink", "" + deTails, "₱ " + aMount));
mAdapter.notifyDataSetChanged();