Question

我在我的项目中使用片段，我想在项目的一部分中使用sqlite数据库，但我在以下类的部分内容有错误

package com.androiddeft.navigationdrawer;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.TextView;


import com.androiddeft.navigationdrawer.fragments.CustomersFragment;

import java.util.List;

public class MyListAdapter extends BaseAdapter {
    private Context context;
    private List<Employee> employees;

    public MyListAdapter(Context context, List<Employee> employees){
        this.context = context;
        this.employees = employees;
    }

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

    @Override
    public Object getItem(int i) {
        return employees.get(i);
    }

    @Override
    public long getItemId(int i) {
        return employees.get(i).getId();
    }

    @Override
    public View getView(final int position, View view, ViewGroup viewGroup) {

        View rowView = LayoutInflater.from(context).inflate(R.layout.list_item, viewGroup, false);
        TextView txtName = (TextView) rowView.findViewById(R.id.txt_employee_name);
        TextView txtPhone = (TextView) rowView.findViewById(R.id.txt_employee_phone);
        TextView txtAddress = (TextView) rowView.findViewById(R.id.txt_employee_address);
        Button btnEdit = (Button) rowView.findViewById(R.id.btn_edit);
        Button btnDelete = (Button) rowView.findViewById(R.id.btn_delete);

        txtName.setText(employees.get(position).getName());
        txtPhone.setText(employees.get(position).getPhone());
        txtAddress.setText(employees.get(position).getAddress());

        btnEdit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                **((CustomersFragment) context).editEmployee(employees.get(position))**;
            }
        });

        btnDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new DatabaseHelper(context).deleteEmployee(employees.get(position));
                employees.remove(position);
                notifyDataSetChanged();
            }
        });

        return rowView;
    }
}

我在android studio IDE上的错误信息是：

不可转换的类型;无法投射＆＃39; android.content.Context＆＃39;来自com.androiddeft.navigationdrawer.fragments.CustomersFragment

注意：

Customersfragment是我的片段名称，我在第59行有错误里面有两颗星符号

Answer 1

适配器已有上下文。只是使用它。

  public class MyListAdapter extends BaseAdapter {
    private Context context;
    private List<Employee> employees;
    private CustomersFragment fragment;

    public MyListAdapter(Context context, List<Employee> employees, CustomersFragment fragment){
        this.context = context;
        this.employees = employees;
        this.fragment = fragment;
    }

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

    @Override
    public Object getItem(int i) {
        return employees.get(i);
    }

    @Override
    public long getItemId(int i) {
        return employees.get(i).getId();
    }

    @Override
    public View getView(final int position, View view, ViewGroup viewGroup) {

        View rowView = LayoutInflater.from(context).inflate(R.layout.list_item, viewGroup, false);
        TextView txtName = (TextView) rowView.findViewById(R.id.txt_employee_name);
        TextView txtPhone = (TextView) rowView.findViewById(R.id.txt_employee_phone);
        TextView txtAddress = (TextView) rowView.findViewById(R.id.txt_employee_address);
        Button btnEdit = (Button) rowView.findViewById(R.id.btn_edit);
        Button btnDelete = (Button) rowView.findViewById(R.id.btn_delete);

        txtName.setText(employees.get(position).getName());
        txtPhone.setText(employees.get(position).getPhone());
        txtAddress.setText(employees.get(position).getAddress());

        btnEdit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                fragment.editEmployee(employees.get(position));
            }
        });

        btnDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new DatabaseHelper(context).deleteEmployee(employees.get(position));
                employees.remove(position);
                notifyDataSetChanged();
            }
        });

        return rowView;
    }
}

如果从Fragment类设置此适配器，则只需使用此

adapter = new MyListAdapter(getActivity(), employees,CustomersFragment.this);

就是这样。

您可以点击此链接获取更多信息 Call a Fragment method from an Adapter

Answer 2

在Fragment中使用getActivity()来获取可以使用构造函数传递给MyListAdapter类的Context。这是有效的，因为Activity继承自Context。

作为替代方案，您可以使用getApplicationContext()来获取上下文。

我在这堂课有错误如何解决？

2 个答案: