Android ListView 显示多种数据类型

ListView往往可能会有不同的数据类型，单类型的数据可能运用会比较少些，这也是最近项目中的一个需求{在发送消息的时候，需要选择联系人，而联系人列表由英文字母索引+联系人组成}，上一篇文章只是一个基调，这篇是更复杂的情况；
先看一下效果图

最开始的时候，打算把两种数据类型放入一个List<Object>中，参考上一篇随笔的状态保持的实现，在代码写完了开始测试的时候，发现问题众多，上下滚动的时候左边的CheckBox的选择状态没有很好的保存，会出现混乱选择的情况，于是参考网上的一些做法{寻找的参考方法并没有描述像这样稍稍复杂点的情况，都是TextView，没有状态的保持，没有View的重用，所以写了这篇随笔}并延伸总结；
MutiTypeAdapter.java

public class MutiTypeAdapter extends BaseAdapter {
    private OnSelectedItemChanged listener;
    private List<ListItem> list;
    private LayoutInflater inflater;

    public MutiTypeAdapter(Context context, List<ListItem> list,
            OnSelectedItemChanged listener) {
        super();
        this.list = list;
        inflater = LayoutInflater.from(context);
        this.listener = listener;
    }

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

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // 重点
        View view = list.get(position).getView(convertView, inflater);
        if (list.get(position).getClass() == BEntity.class) { // 如果是BEntity，也就是上面图中左边有CheckBox的项
            final BEntity entity = (BEntity) list.get(position);
            final CheckBox cb = entity.cbox;
            cb.setChecked(entity.isChecked());
            cb.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    entity.setChecked(cb.isChecked()); // 更改List中Entity的选择状态
                    if (listener != null) {
                        listener.onClick(getSelectedItem(list)); // 接口的思想暴露给Activity选择了多少项，当然也可以具体点通知Activity选择了哪些项
                    }
                }
            });
        }
        return view;
    }

    public int getSelectedItem(List<ListItem> list) { // 获取选择了多少项
        int i = 0;
        for (ListItem item : list) {
            if (item.isChecked()) {
                i++;
            }
        }
        return i;
    }

    public interface OnSelectedItemChanged {
        public void onClick(int count);
    }
}

上面是数据源适配器，最开始的时候我在getView方法中对Item进行数据类的判断(AEntity/BEntity)，再决定是选择加载哪一个layout，结果发现在重用View的时候很混乱，所以改为上面的实现方法；
AEntity和BEntity都继承自接口ListItem

public class AEntity implements ListItem {
    private String str;

    public AEntity(String str) {
        super();
        this.str = str;
    }

    @Override
    public View getView(View convertView, LayoutInflater inflater) {
        Holder holder = null;
        if (convertView == null
                || convertView.getTag().getClass() != Holder.class) {
            holder = new Holder();
            convertView = inflater.inflate(getLayoutId(), null);
            TextView tv = (TextView) convertView.findViewById(R.id.title_tv);
            holder.tv = tv;
            convertView.setTag(holder);
        } else {
            holder = (Holder) convertView.getTag();
        }
        holder.tv.setText(str);
        return convertView;
    }

    class Holder {
        TextView tv;
    }

    @Override
    public int getLayoutId() {
        return R.layout.title;
    }

    @Override
    public boolean isChecked() { // 此Entity相当于是标题项，没有CheckBox，所以永远返回false
        return false;
    }
}

public class BEntity implements ListItem {
    private boolean isChecked = false;
    private String str;

    public boolean isChecked() {
        return isChecked;
    }

    public void setChecked(boolean isChecked) {
        this.isChecked = isChecked;
    }

    public BEntity(String str) {
        super();
        this.str = str;
    }

    @Override
    public int getLayoutId() {
        return R.layout.child;
    }

    public CheckBox cbox;

    @Override
    public View getView(View convertView, LayoutInflater inflater) {
        Holder holder = null;
        if (convertView == null
                || convertView.getTag().getClass() != Holder.class) {
            holder = new Holder();
            convertView = inflater.inflate(getLayoutId(), null);
            TextView tv = (TextView) convertView.findViewById(R.id.item_tv);
            CheckBox cb = (CheckBox) convertView.findViewById(R.id.item_cb);
            holder.tv = tv;
            holder.cb = cb;
            convertView.setTag(holder);
        } else {
            holder = (Holder) convertView.getTag();
        }
        holder.tv.setText(str);
        final CheckBox cb = holder.cb;
        this.cbox = cb;return convertView;
    }

    class Holder {
        TextView tv;
        CheckBox cb;
    }
}

ListItem.java

public interface ListItem {
    public boolean isChecked(); // 当前项是否选中

    public int getLayoutId();

    public View getView(View convertView, LayoutInflater inflater); // 返回Adapter中需要返回的View
}

在MainActivity中，模拟数据源并绑定到ListView列表；

public class MainActivity extends Activity {
    ListView lv;
    MutiTypeAdapter adapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView) findViewById(R.id.lv);
        setAdapter();
    }

    private void setAdapter() {
        List<ListItem> list = new ArrayList<ListItem>();
        for (int i = 0; i < 50; i++) {
            if (i % 2 == 0) {
                list.add(new AEntity("item - " + i));
            } else {
                list.add(new BEntity("item - " + i));
            }
        }
        OnSelectedItemChanged listener = new OnSelectedItemChanged() {

            @Override
            public void onClick(int count) {
                Log.e("SelectedCount", count + "");
            }
        };
        adapter = new MutiTypeAdapter(getApplicationContext(), list, listener);
        lv.setAdapter(adapter);
    }
}

OK，通过几步就实现了所想要的功能！