java - 如何删除 fragment 中的 ListView 项？

Question

我试图从 ListView 中删除一个项目，但是有一个问题..我正在使用一个 fragment ，但我不知道如何获得“删除图像按钮”来添加一个 onClickListener...这是我在 payment_list_view.xml 中删除按钮的 xml:

<ImageButton
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:src="@drawable/trash_icon"
            android:padding="10dp"
            android:id="@+id/delete_payment_btn"
            android:background="@android:color/white" />

然后，我有我的 PaymentFragment，其中包含我的 ListView :

 package com.nicola.baccillieri.splitpayment;




public class PaymentFragment extends Fragment {

private String descString;
private int price;
private String payedBy;
private ArrayList<String> descPayArray;
private ArrayList<Integer> priceArray;
private ArrayList<String> payedByArray;
int trash;
PaymentAdapter customAdapter;
private final static String SHARED_PREFS = "sharedPrefs";
FirebaseFirestore db;



@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    db = FirebaseFirestore.getInstance();
    trash = (R.drawable.trash_icon);
    descPayArray = new ArrayList<>();
    priceArray = new ArrayList<>();
    payedByArray = new ArrayList<>();


}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {


    final View rootView=inflater.inflate(R.layout.payments_fragment,container,false);

    ProgressBar detailsPb = rootView.findViewById(R.id.details_pb);
    detailsPb.getIndeterminateDrawable().setColorFilter(0XFF3F51B5,
            PorterDuff.Mode.MULTIPLY);
    detailsPb.setVisibility(View.VISIBLE);

    final ListView listView = rootView.findViewById(R.id.paymentLv);
    String email = getEmail();
    String groupName = getActivity().getIntent().getStringExtra("title");

    DocumentReference docRef = db.collection("users").document(email).collection("Group").document(groupName);

    docRef.collection("Payments")
            .get()
            .addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                @Override
                public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                    for (QueryDocumentSnapshot document : queryDocumentSnapshots) {

                        //Extracting payment description from each document

                        descString = document.getId();
                        descPayArray.add(descString);

                        //Extracting cost and who payed from each document

                        price = document.getLong("cost").intValue();
                        priceArray.add(price);

                        payedBy = document.getString("payed by");
                        payedByArray.add(payedBy);
                        trash = R.drawable.trash_icon;
                        customAdapter = new PaymentAdapter(getActivity(), descPayArray, payedByArray, priceArray, trash);
                        listView.setAdapter(customAdapter);
                        ProgressBar detailsPb =  rootView.findViewById(R.id.details_pb);
                        detailsPb.setVisibility(View.GONE);
  // That's the line that cause the error
                        ImageButton deleteBtn = rootView.findViewById(R.id.delete_payment_btn);
                        deleteBtn.setOnClickListener(new View.OnClickListener() {
                            @Override
                            public void onClick(View v) {
                                String groupName = getActivity().getIntent().getStringExtra("title");
                                int positionToRemove = (int) v.getTag();
                                String email = getEmail();
                                String paymentToRemove = descPayArray.get(positionToRemove);
                                DocumentReference docRef = db.collection("users").document(email).collection("Group").document(groupName).collection("Payments").document(paymentToRemove);
                                docRef.delete();

                                descPayArray.remove(positionToRemove);
                                customAdapter.notifyDataSetChanged();
                            }
                        });

                    }
                    // If there isn't any payment display a blank activity
                    ProgressBar detailsPb =  rootView.findViewById(R.id.details_pb);
                    detailsPb.setVisibility(View.GONE);


                }
            })
            .addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    ProgressBar detailsPb =  rootView.findViewById(R.id.details_pb);
                    detailsPb.setVisibility(View.GONE);
                    Toast.makeText(getContext(), "Failed to load payments", Toast.LENGTH_LONG).show();
                }
            });



    return rootView;

}


public String getEmail() {

    SharedPreferences sharedPreferences = this.getActivity().getSharedPreferences(SHARED_PREFS, MODE_PRIVATE);
    String email = (sharedPreferences.getString("email", ""));
    return email;
}}

最后，文件 group_detail_activity.xml 包含我的带有选项卡布局的 2 fragment 。现在，应用程序在必须显示 PaymentFragment 时崩溃，因为 ImageButton deleteBtn = rootView.findViewById(R.id.delete_payment_btn);说

`java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference".

那是因为我的 rootView 包含 payment_fragment.xml，而不是 payment_list_view.xml。所以它找不到按钮。我尝试添加 final View rootListView=inflater.inflate(R.layout.payment_list_view,container,false);然后它显示 ListView ，但是当我单击删除按钮时，它什么也没做。我该怎么办？

那是我的 PaymentAdapter:

package com.nicola.baccillieri.splitpayment;


public class PaymentAdapter extends BaseAdapter {

private Context context;
private ArrayList<String> payDesc;
private ArrayList<String> payedBy;
private ArrayList<Integer> price;
private int trash;
LayoutInflater inflater;


public PaymentAdapter(Context context, ArrayList<String> payDesc, ArrayList<String> payedBy, ArrayList<Integer> price, int trash) {
    this.context = context;
    this.payDesc = payDesc;
    this.payedBy = payedBy;
    this.price = price;
    this.trash = trash;
    inflater = (LayoutInflater.from(context));
}

@Override
public int getCount() {
    return payDesc.size();
}

@Override
public Object getItem(int position) {
    return payDesc.get(position);
}

@Override
public long getItemId(int position) {
    return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    convertView = inflater.inflate(R.layout.payment_list_view, null);

    TextView paymentDesc = convertView.findViewById(R.id.payedDescTv);
    TextView payedByTv = convertView.findViewById(R.id.payedByTv);
    TextView priceTv = convertView.findViewById(R.id.priceTv);
    ImageButton trashIcon = convertView.findViewById(R.id.delete_payment_btn);

    paymentDesc.setText(payDesc.get(position));
    payedByTv.setText("Payed by " + payedBy.get(position));
    priceTv.setText(String.valueOf(price.get(position)) + "€");
    trashIcon.setImageResource(trash);
    trashIcon.setTag(position);

    return convertView;
}}

问题是我需要从 listview 和 firebase 中删除该项目...所以我需要 getEmail() 方法和 PaymentFragment 中的 getExtra ..如果我将监听器放在适配器上，如何我可以删除 o Firebase 吗？

Answer 1

试试这个方法。在列表上点击你可以删除项目

    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

            payedByArray.remove(position);
            adapter.notifyItemRemoved(position);

        }
    });

其他方法是将Delete Button 放在您的payment_list_view 中，然后在Adapter 中您可以在该按钮上点击并删除它