android - ListView项目背景:Android

Question

我有一个问答应用。我想更改 listItem 的颜色是那个作者回答了这个问题。这是一个 fragment

for (int i = 0; i < response.length(); i++) {
                            try {

                                JSONObject obj = response.getJSONObject(i);
                                QuestionGetSet movie = new QuestionGetSet();
                                movie.setQues(obj.getString("abc"));
                                movie.setDate(obj.getString("def"));
                                movie.setNumber(obj.getString("ghi"));
                                farmerName[i] = obj.getString("jkl");
                                cropType[i] = obj.getString("mno");
                                relatedField[i] = obj.getString("pqr");
                                number[i]=obj.getString("stu");
                                // adding movie to movies array
                                movieList.add(movie);
                                if(i==0) {
                                    listView.getChildAt(i).setBackgroundColor(Color.GREEN);
                                }
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }

问题是程序在

处给出 NullPointerException

if(i==0) {
                                          listView.getChildAt(i).setBackgroundColor(Color.GREEN);
                                }

适配器代码:

public class CustomListAdapter extends BaseAdapter {
private Activity activity;
private LayoutInflater inflater;
private List<QuestionGetSet> quesItems;


public CustomListAdapter(Activity activity, List<QuestionGetSet> quesItems) {
    this.activity = activity;
    this.quesItems = quesItems;
}



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

@Override
public Object getItem(int location) {
    return quesItems.get(location);
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    if (inflater == null)
        inflater = (LayoutInflater) activity
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    if (convertView == null)
        convertView = inflater.inflate(R.layout.custom_list_layout_home, null);

    TextView question = (TextView) convertView.findViewById(R.id.txt_questions);
    TextView date = (TextView) convertView.findViewById(R.id.txt_date);
    TextView number = (TextView) convertView.findViewById(R.id.txt_asked_by);

    // getting movie data for the row
    QuestionGetSet m = quesItems.get(position);

    // title
    question.setText(m.getQues());

    // rating
    date.setText(m.getDate());

    // release year
    number.setText(m.getNumber());

    return convertView;
}

我希望我清楚。请帮忙。

Answer 1

这是因为您在实际设置 ListView 之前调用了 listView.getChildAt(i)。尝试在适配器中更改背景颜色 getView()。

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    if (inflater == null)
        inflater = (LayoutInflater) activity
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    if (convertView == null)
        convertView = inflater.inflate(R.layout.custom_list_layout_home, null);

    TextView question = (TextView) convertView.findViewById(R.id.txt_questions);
    TextView date = (TextView) convertView.findViewById(R.id.txt_date);
    TextView number = (TextView) convertView.findViewById(R.id.txt_asked_by);

    // getting movie data for the row
    QuestionGetSet m = quesItems.get(position);

    // title
    question.setText(m.getQues());

    // rating
    date.setText(m.getDate());

    if (position == 0) {
        convertView.setBackgroundColor(Color.GREEN);
    }

    return conertView;
}

希望对你有用。