Question

我正在尝试创建一个包含List的Tabbed Activity。我创建了Tabbed Activity，我想在片段中创建列表。每个列表项包含2个ImageView和4个TextView。因此，我创建了一个自定义类和一个自定义ArrayAdapter。这是代码 -

Coins.java - 这是标签Activity的片段。

package com.example.android.cotescol;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import java.util.ArrayList;
public class Coins extends android.support.v4.app.Fragment{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.currency_list, container, false);

        final ArrayList<CoinObject> coins = new ArrayList<Currency>();

        coins.add(new CoinObject(1, "India", 1947));
        coins.add(new CoinObject(1, "India", 1947));

        CoinAdapter itemsAdapter = new CoinAdapter(this, coins);
        ListView listView = (ListView) findViewById(R.id.list);
        listView.setAdapter(itemsAdapter);

        return rootView;
    }
}

CoinObject.java - 这是一个自定义类，其中每个对象都包含硬币的所有细节。

package com.example.android.cotescol;

import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

public class CoinObject {

    private final static int NO_IMAGE_AVAILABLE = R.drawable.nia;
    private final static String NOT_AVAILABLE = "Material Not Specified";
    private final static double NOT_KNOWN = 0.00;

    private int denomination;
    private String country;
    private String countryCode;
    private int year;
    private int obverseImageResourceId = NO_IMAGE_AVAILABLE;
    private int reverseImageResourceId = NO_IMAGE_AVAILABLE;
    private String material = NOT_AVAILABLE;
    private double diameter = NOT_KNOWN;
    private double weight = NOT_KNOWN;
    private double thickness = NOT_KNOWN;
    private double value = NOT_KNOWN;

    public CoinObject(int denomination, String country, int year, int obverseImageResourceId, int reverseImageResourceId , double diameter, double thickness, String material, double weight, double value) {
        this.denomination = denomination;
        this.country = country;
        this.year = year;
        this.obverseImageResourceId = obverseImageResourceId;
        this.reverseImageResourceId = reverseImageResourceId;
        this.diameter = diameter;
        this.thickness = thickness;
        this.material = material;
        this.weight = weight;
        this.value = value;
        this.countryCode = getCountryCode(country);
    }

    public CoinObject(int denomination, String country, int year, double diameter, double thickness, String material, double weight, double value) {
        this.denomination = denomination;
        this.country = country;
        this.year = year;
        this.diameter = diameter;
        this.thickness = thickness;
        this.material = material;
        this.weight = weight;
        this.value = value;
        this.countryCode = getCountryCode(country);
    }

    public CoinObject(int denomination, String country, int year) {
        this.denomination = denomination;
        this.country = country;
        this.year = year;
        this.countryCode = getCountryCode(country);
    }

    public String getCountryCode(String countryName) {
        // Get all country codes in a string array.
        String[] isoCountryCodes = Locale.getISOCountries();
        Map<String, String> countryMap = new HashMap<>();
        // Iterate through all country codes:
        for (String code : isoCountryCodes) {
            // Create a locale using each country code
            Locale locale = new Locale("", code);
            // Get country name for each code.
            String name = locale.getDisplayCountry();
            // Map all country names and codes in key - value pairs.
            countryMap.put(name, code);
        }
        // Get the country code for the given country name using the map.
        // Here you will need some validation or better yet
        // a list of countries to give to user to choose from.
        String countryCode = countryMap.get(countryName); // "NL" for Netherlands.  

        return countryCode;
    }

    public int getDenomination() { return denomination; }
    public int getYear() { return year; }
    public int getObverseImageResourceId() { return obverseImageResourceId; }
    public int getReverseImageResourceId() { return reverseImageResourceId; }
    public double getDiameter() { return diameter; }
    public double getWeight() { return weight; }
    public double getThickness() { return thickness; }
    public double getValue() { return value; }
    public String getCountry() { return country; }
    public String getCountryCode() { return countryCode; }
    public String getMaterial() { return material; }
}

CoinAdapter.java - 这是一个自定义的ArrayAdapter

package com.example.android.cotescol;

import android.content.Context;
import android.support.annotation.NonNull;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.ArrayList;

public class CoinAdapter extends ArrayAdapter<CoinObject>{
    public CoinAdapter(Context context, ArrayList<CoinObject> currencies) {
        super(context, 0, currencies);
    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View listItemView = convertView;
        if (listItemView == null) {
            listItemView = LayoutInflater.from(getContext()).inflate(R.layout.list_item, parent, false);
        }

        CoinObject currentCoinObject = getItem(position);

        TextView denominationTextView = (TextView) listItemView.findViewById(R.id.denomination_text_view);
        denominationTextView.setText(currentCoinObject.getDenomination());

        TextView countryTextView = (TextView) listItemView.findViewById(R.id.country_text_view);
        countryTextView.setText(currentCoinObject.getCountry() + "(" + currentCoinObject.getCountryCode() + ")");

        TextView yearTextView = (TextView) listItemView.findViewById(R.id.year_text_view);
        yearTextView.setText(currentCoinObject.getYear());

        ImageView obverseImageView = (ImageView) listItemView.findViewById(R.id.obverse_image_view);
        obverseImageView.setImageResource(currentCoinObject.getObverseImageResourceId());

        ImageView reverseImageView = (ImageView) listItemView.findViewById(R.id.reverse_image_view);
        reverseImageView.setImageResource(currentCoinObject.getReverseImageResourceId());

        return listItemView;
    }
}

在Coins.java文件中，我在创建CoinAdapter类的实例时遇到错误。 findViewById（）也以红色显示。 Error Picture

如果有人引导我以正确的方式去做，那将会非常有帮助。在此先感谢。

Answer 1

替换：

CoinAdapter itemsAdapter = new CoinAdapter(this, coins);

使用：

CoinAdapter itemsAdapter = new CoinAdapter(getActivity(), coins);

替换：

ListView listView = (ListView) findViewById(R.id.list);

使用：

ListView listView = (ListView) rootView.findViewById(R.id.list);

ArrayAdapter显示错误：选项卡式活动和ListView

1 个答案: