Question

我有一个适配器，它为listView显示两个视图 - 一个checkedtextview和一个普通的textview。当用户在MarkMode时，我想使用checkedtextview，这样他/她可以标记项目，我想在用户不在MarkMode时使用textview。

所以这是我的原始代码，只有MarkMode。

public class ContactsAdapter extends BaseAdapter {

    private List<Contact> mData;
    private LayoutInflater mInflater;
    private Context context;

    public ContactsAdapter(List<Contact> mData, Context context) {
        this.mData = mData;
        this.context = context;
        mInflater = LayoutInflater.from(context);
    }

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

    @Override
    public String getItem(int position) {
        switch (context.getSharedPreferences("settings",
                HomeScreenActivity.MODE_PRIVATE).getInt("displayChoice", -1)) {
        case 1:
            return mData.get(position).getLastName() + " "
                    + mData.get(position).getFirstName();
        case 2:
            return mData.get(position).getFirstName() + " "
                    + mData.get(position).getMobileNumber();
        case 3:
            return mData.get(position).getLastName() + " "
                    + mData.get(position).getMobileNumber();
        default:
            return mData.get(position).getFirstName() + " "
                    + mData.get(position).getLastName();
        }
    }

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

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

        CheckedTextView result;

        if (convertView == null) {
            result = (CheckedTextView) mInflater.inflate(
                    R.layout.home_screen_contacts_mark_view, parent, false);
        } else {
            result = (CheckedTextView) convertView;
        }

        final String contactRow = getItem(position);
        result.setText(contactRow);
        result.setBackgroundResource(R.drawable.list_selector);

        return result;
    }

}

现在我将其更改为此，以便我可以更改名为isMarkMode的类变量，以便显示不同的视图......

public class ContactsAdapter extends BaseAdapter {

    private List<Contact> mData;
    private LayoutInflater mInflater;
    private Context context;
    public static boolean inMarkMode = false;
    public ContactsAdapter(List<Contact> mData, Context context) {
        this.mData = mData;
        this.context = context;
        mInflater = LayoutInflater.from(context);
    }

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

    @Override
    public String getItem(int position) {
        switch (context.getSharedPreferences("settings",
                HomeScreenActivity.MODE_PRIVATE).getInt("displayChoice", -1)) {
        case 1:
            return mData.get(position).getLastName() + " "
                    + mData.get(position).getFirstName();
        case 2:
            return mData.get(position).getFirstName() + " "
                    + mData.get(position).getMobileNumber();
        case 3:
            return mData.get(position).getLastName() + " "
                    + mData.get(position).getMobileNumber();
        default:
            return mData.get(position).getFirstName() + " "
                    + mData.get(position).getLastName();
        }
    }

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

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

                CheckedTextView result = null;
        TextView normalResult = null;

        if (inMarkMode) {
            if (convertView == null) {
                result = (CheckedTextView) mInflater.inflate(
                        R.layout.home_screen_contacts_mark_view, parent, false);
            } else {
                result = (CheckedTextView) convertView;
            }
        } else {
            if (convertView == null) {
                normalResult = (TextView) mInflater.inflate(
                        R.layout.home_screen_contacts_view, parent, false);
            } else {
                normalResult = (TextView) convertView;
            }
        }
        final String contactRow = getItem(position);
        result.setText(contactRow);
        result.setBackgroundResource(R.drawable.list_selector);
        normalResult.setText(contactRow);
        normalResult.setBackgroundResource(R.drawable.list_selector);

        if (inMarkMode) {
            return result;
        } else {
            return normalResult;
        }
    }
    }

}

最初它看起来像是在工作，但随后它停止了，我收到一个logcat错误，指出此行上有一个NullPointerException：result.setText(contactRow);

我该如何解决这个问题？任何帮助将不胜感激。

Answer 1

result为inMarkMode时，

false未初始化。因此，如果在result.setText(contactRow);为inMarkMode true时阻止，则将final String contactRow = getItem(position); if (inMarkMode) { //.....your code here.. result.setText(contactRow); result.setBackgroundResource(R.drawable.list_selector); } else { //.....your code here.. normalResult.setText(contactRow); normalResult.setBackgroundResource(R.drawable.list_selector); }移到内部：

{{1}}

Answer 2

将您的Getview方法更改为此

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

            CheckedTextView result = null;
            TextView normalResult = null;

            if (inMarkMode) {
                if (convertView == null) {
                    result = (CheckedTextView) mInflater.inflate(
                            R.layout.home_screen_contacts_mark_view, parent, false);
                } else {
                    result = (CheckedTextView) convertView;
                }
            } else {
                if (convertView == null) {
                    normalResult = (TextView) mInflater.inflate(
                            R.layout.home_screen_contacts_view, parent, false);
                } else {
                    normalResult = (TextView) convertView;
                }

            }
final String contactRow = getItem(position);

            if (inMarkMode) {

            result.setText(contactRow);
            result.setBackgroundResource(R.drawable.list_selector);
                return result;
            } else {
            normalResult.setText(contactRow);
            normalResult.setBackgroundResource(R.drawable.list_selector);
                return normalResult;
            }
        }
        }

Android：适配器显示两个不同的视图，但获取空指针

2 个答案: