java - android中的子类ArrayAdapter用于显示ArrayList

Question

我已经问过类似的问题 here一位用户建议对 ArrayAdapter 进行子类化，但我对此有疑问。 这是我的问题:

我使用HashMap<String, String>和一个 SimpleAdapter对象在我的 ListView 中显示用户数据，但现在我想替换 HashMap<String, String>与 ArrayList<User>();包含真实的用户对象。

这是旧代码:

HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_USERNAME, c.getString(TAG_USERNAME));
                map.put(TAG_FIRSTNAME, c.getString(TAG_FIRSTNAME));
                map.put(TAG_LASTNAME, c.getString(TAG_LASTNAME));
                map.put(TAG_ADDRESS, c.getString(TAG_ADDRESS));
                usersList.add(map);

[...]

ListAdapter adapter = new SimpleAdapter(this, usersList,
                    R.layout.single_user, new String[] { TAG_USERNAME,
                            TAG_FIRSTNAME, TAG_LASTNAME, TAG_ADDRESS },
                    new int[] { R.id.textViewUsername, R.id.textViewFirstName,
                            R.id.textViewLastName, R.id.textViewAddress });

现在，按照建议，我尝试对 ArrayAdapter 进行子类化，但我没有计划如何 getView(int, View, ViewGroup)应该看起来像，以实现我的目标。

这是我当前的代码:

public class UserArrayAdapter extends ArrayAdapter<User> {

    private Context mcon;
    private List<User> userList;

    public UserArrayAdapter(Context context, int resource,
            List<User> userList) {
        super(context, resource);
        mcon = context;
        this.userList = userList;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        for (User usr : userList) {
            findViewById(R.id.textViewUsername).setText(usr.getFirstName());
        }
        return super.getView(position, convertView, parent);
    }

}

这是用户类:

public class User {

    private String username, firstName, lastName, address;

    public User(String username, String firstName, String lastName,
            String address) {
        setUsername(username);
        setFirstName(firstName);
        setLastName(lastName);
        setAddress(address);
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        if (username == null) {
            throw new IllegalArgumentException("username is null.");
        }
        this.username = username;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        if (firstName == null) {
            throw new IllegalArgumentException("firstName is null.");
        }
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        if (lastName == null) {
            throw new IllegalArgumentException("lastName is null.");
        }
        this.lastName = lastName;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        if (address == null) {
            throw new IllegalArgumentException("address is null.");
        }
        this.address = address;
    }
}

我想我会这样调用它:

    ListAdapter ad = new UserArrayAdapter(this, R.layout.single_user, usersArrList);

任何帮助将不胜感激。

Answer 1

我建议完全绕过ArrayAdapter，因为您将进行自定义工作，因此您将在内部重复适配器所做的工作。无论如何，实现都是微不足道的。只是子类BaseAdapter:

public class UserAdapter extends BaseAdapter {
    private final List<User> mUsers;
    private final LayoutInflater mInflater;

    public UserAdapter(Context ctx, Collection<User> users) {
        mUsers = new ArrayList<User>();
        mInflater = LayoutInflater.from(ctx);
        if (users != null) {
            mUsers.addAll(users);
        }
    }

    @Override
    public int getCount() {
        // Just return the number of users in your data set
        return mUsers.size();
    }

    @Override
    public long getItemId(int pos) {
        // Mostly irrelevant if you're not using Cursors
        return pos;
    }

    @Override
    public User getItem(int pos) {
        // Just return the item at the specified position
        return mUsers.get(pos);
    }

    @Override
    public View getView(int pos, View convertView, ViewGroup parent) {
        UserViewHolder uvh;

        if (convertView == null) {
            // Only inflate the layout if there's not already a recycled view
            convertView = mInflater.inflate(R.layout.single_user, parent, false);

            // Tag the view with a class holding the views found with 
            // findViewById() to prevent lookups later
            uvh = new UserViewHolder(convertView);
            convertView.setTag(uvh);
        } else {
            // If the view is non-null, then you will have already
            // created the view holder and set it as a tag
            uvh = (UserViewHolder) convertView.getTag();
        }

        // Now just get the user at the specified position and
        // set up the view as necessary
        User user = getItem(pos);
        uvh.usernameTxt.setText(user.getUsername());

        return convertView;
    }

    public static class UserViewHolder {
        public final TextView usernameTxt;

        public UserViewHolder(View v) {
            usernameTxt = (TextView) v.findViewById(R.id.textViewUsername);
        }
    }
}