ListView 崩溃，无法处理 holder class

Question

你好 Whosebugers，

经过数年、数月和数周的潜伏，我终于遇到了 android 开发者网站和现有帖子都无法解决的问题，所以请尽可能帮助我解决这个小问题。

我想用我的代码实现什么？（更新！） → 我想创建一个带有复选框的列表，在选择其中几个之后我想将选中的转移到下一个 Activity。以下代码不会解决有关传递的问题。我想通过提供的 2 classes 实现的是，我可以检查项目上下滚动，并且它们会记住它们是否被检查过。

我的问题（已更新！） → ListView 中的 CheckBoxes 不记得在滚动回它们的位置后是否被选中。

我已经将有问题的代码封装到这个单独的项目中

这是代码。请注意，Planet-class 和 PlanetAdapter 在同一个 JavaClass 中。

------------> MainAcitivty<---------------------

package com.example.christian.listviewwithcheckboxes;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.CheckBox;
import android.widget.ListView;
import android.widget.Toast;


import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    ListView lv;
    ArrayList<Planet> planetList;
    PlanetAdapter plAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        lv = (ListView) findViewById(R.id.listview);
        displayPlanetList();

        lv.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                CheckBox checkbox = (CheckBox) view.findViewById(R.id.chk_box);
                checkbox.setChecked(!checkbox.isChecked());

                Planet p = planetList.get(position);
                p.setSelected(checkbox.isChecked());
                plAdapter.notifyDataSetChanged();

                Toast.makeText(MainActivity.this, "Checkbox checked/unchecked", Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void displayPlanetList() {
        planetList = new ArrayList<Planet>();

        planetList.add((new Planet("please ", 29)));
        planetList.add((new Planet("help ", 30)));
        planetList.add((new Planet("me", 31)));
        planetList.add((new Planet("earth", 1)));
        planetList.add((new Planet("moon", 2)));
        planetList.add((new Planet("mercury", 3)));
        planetList.add((new Planet("jupiter", 4)));
        planetList.add((new Planet("venus", 5)));
        planetList.add((new Planet("pluto", 6)));
        planetList.add((new Planet("mars", 7)));
        planetList.add((new Planet("KOI-1843.03", 8)));
        planetList.add((new Planet("KOI-1843.01", 9)));
        planetList.add((new Planet("KOI-1843.02", 10)));
        planetList.add((new Planet("Kepler-9b", 11)));
        planetList.add((new Planet("Kepler-9c", 12)));
        planetList.add((new Planet("Kepler-9d", 13)));
        planetList.add((new Planet("GJ 160.2b", 14)));
        planetList.add((new Planet("HD 240210b", 15)));
        planetList.add((new Planet("OGLE-05-309L b", 16)));
        planetList.add((new Planet("WASP-82 b", 17)));
        planetList.add((new Planet("Gliese 1214b", 18)));
        planetList.add((new Planet("Kepler-153b", 19)));
        planetList.add((new Planet("Kepler-153c", 20)));
        planetList.add((new Planet("HD 4203 b", 21)));
        planetList.add((new Planet("HD 4203 c", 22)));
        planetList.add((new Planet("HD 179079 b", 23)));
        planetList.add((new Planet("HD 187123 b", 24)));
        planetList.add((new Planet("HD 187123 c", 25)));
        planetList.add((new Planet("Kepler-431 b", 26)));
        planetList.add((new Planet("Kepler-431 b", 27)));
        planetList.add((new Planet("Kepler-431 d", 28)));

        plAdapter = new PlanetAdapter(planetList, this);
        lv.setAdapter(plAdapter);
    }
}

------------> MainAcitivty<---------------------

------------> PlanetAdapter<---------------------

package com.example.christian.listviewwithcheckboxes;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.TextView;

import java.util.List;

class Planet {
    String name;
    int distance;
    boolean selected = false;


    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getDistance() {
        return distance;
    }

    public void setDistance(int distance) {
        this.distance = distance;
    }

    public boolean isSelected() {
        return selected;
    }

    public void setSelected(boolean selected) {
        this.selected = selected;
    }

    public Planet(String name, int distance) {
        super();
        this.name = name;
        this.distance = distance;
    }

}

public class PlanetAdapter extends ArrayAdapter<Planet> {

    private List<Planet> planetList;
    private Context context;


    public PlanetAdapter(List<Planet> planetList, Context context) {
        super(context, R.layout.single_listview_item, planetList);
        this.planetList = planetList;
        this.context = context;
    }

    private static class PlanetHolder {
        public TextView planetName;
        public TextView distView;
        public CheckBox chkBox;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        PlanetHolder holder = new PlanetHolder();

        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService((Context.LAYOUT_INFLATER_SERVICE));
            v = inflater.inflate(R.layout.single_listview_item, null);

            holder.planetName = (TextView) v.findViewById(R.id.name);
            holder.distView = (TextView) v.findViewById(R.id.dist);
            holder.chkBox = (CheckBox) v.findViewById(R.id.chk_box);

            v.setTag(holder);

        } else {
            holder = (PlanetHolder) v.getTag();
        }

        Planet p = planetList.get(position);
        holder.planetName.setText((p.getName()));
        holder.distView.setText("" + p.getDistance());
        holder.chkBox.setChecked(p.isSelected());

        holder.chkBox.setTag(p);

        return v;
    }
}

------------> PlanetAdapter<---------------------

请 Whosebug 团队前来救援:)

此致克里斯

编辑（更新）：此时没有发生错误，但是复选框不记得是否在上下滚动时被选中。

PS: 谢谢你的帮助，帮了我很大的忙，非常感谢。

Answer 1

您应该将 holder.chkBox.setTag(p); 替换为 v.setTag(p)。此时，else 语句将始终设置 holder 为 null.

Answer 2

由于我们在评论中的对话，我更新了我的回答。我希望，它会起作用 :-) 我没有测试它。

主要活动

public class MainActivity extends AppCompatActivity {

    ListView lv;
    ArrayList<Planet> planetList;
    PlanetAdapter plAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        lv = (ListView) findViewById(R.id.listview);
        displayPlanetList();

        lv.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
                CheckBox checkbox = (CheckBox) view.findViewById(R.id.chk_box);
                checkbox.setChecked(!checkbox.isChecked());

                Planet p = planetList.get(position);
                p.setSelected(checkbox.isChecked());
                plAdapter.notifyDataSetChanged();

                Toast.makeText(this, "Clicked, state is " + isChecked, Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void displayPlanetList() {
        planetList = new ArrayList<Planet>();
        planetList.add((new Planet("please ", 29)));
        planetList.add((new Planet("help ", 30)));
        planetList.add((new Planet("me", 31)));
        planetList.add((new Planet("earth", 1)));
        planetList.add((new Planet("moon", 2)));
        planetList.add((new Planet("mercury", 3)));
        planetList.add((new Planet("jupiter", 4)));
        planetList.add((new Planet("venus", 5)));
        planetList.add((new Planet("pluto", 6)));
        planetList.add((new Planet("mars", 7)));
        planetList.add((new Planet("KOI-1843.03", 8)));
        planetList.add((new Planet("KOI-1843.01", 9)));
        planetList.add((new Planet("KOI-1843.02", 10)));
        planetList.add((new Planet("Kepler-9b", 11)));
        planetList.add((new Planet("Kepler-9c", 12)));
        planetList.add((new Planet("Kepler-9d", 13)));
        planetList.add((new Planet("GJ 160.2b", 14)));
        planetList.add((new Planet("HD 240210b", 15)));
        planetList.add((new Planet("OGLE-05-309L b", 16)));
        planetList.add((new Planet("WASP-82 b", 17)));
        planetList.add((new Planet("Gliese 1214b", 18)));
        planetList.add((new Planet("Kepler-153b", 19)));
        planetList.add((new Planet("Kepler-153c", 20)));
        planetList.add((new Planet("HD 4203 b", 21)));
        planetList.add((new Planet("HD 4203 c", 22)));
        planetList.add((new Planet("HD 179079 b", 23)));
        planetList.add((new Planet("HD 187123 b", 24)));
        planetList.add((new Planet("HD 187123 c", 25)));
        planetList.add((new Planet("Kepler-431 b", 26)));
        planetList.add((new Planet("Kepler-431 b", 27)));
        planetList.add((new Planet("Kepler-431 d", 28)));

        plAdapter = new PlanetAdapter(planetList, this);
        // ListView listView = (ListView) findViewById(R.id.listview);
        lv.setAdapter(plAdapter);


    }
}

在您的适配器中，您可以删除此行：

行星适配器

 holder.chkBox.setOnCheckedChangeListener((MainActivity) context);

Answer 3

实际上我和我的一位同事找到了答案。

http://www.lalit3686.blogspot.in/2012/06/today-i-am-going-to-show-how-to-deal.html

这是一个非常简洁的项目，向您展示了如何设置带有复选框的 ListView。

感谢大家的辛勤付出，特别感谢@RediOne1。

祝你有愉快的一天。

ListView 崩溃，无法处理 holder class

ListView crashes, can't handle holder class

java

android

listview

android-arrayadapter

android-listview

主要活动

行星适配器