Android自定义实现BaseAdapter的优化布局

public class MainActivity extends AppCompatActivity {
  private List<Student> data;
  private ListView mList;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mList = (ListView)findViewById(R.id.mList);
    data = new ArrayList<>();
    Student stu = null;
    for(int i = 0; i < 5; i ++){
      stu = new Student();
      stu.setName("姓名"+ i);
      stu.setSex(i % 2 == 0 ? "男" : "女");
      data.add(stu);
    }
    MyAdapter adapter = new MyAdapter(data);
    mList.setAdapter(adapter);
  }
}

public class MyAdapter extends BaseAdapter {

  private List<Student> data;

  public MyAdapter(List<Student> data) {
    this.data = data;
  }

  @Override
  public int getCount() {
    return data == null ? 0 : data.size();
  }

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

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

  /**
   *
   * @param position
   * @param convertView
   * @param parent
   * @return
   */
   @Override
  public View getView(int position, View convertView, ViewGroup parent) {
   ViewHolder holder = null;
    if(convertView == null){
      //解析布局
      convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item,null);
      //创建ViewHolder持有类
      holder = new ViewHolder();
      //将每个控件的对象保存到持有类中
      holder.tvName = (TextView)convertView.findViewById(R.id.mTv1);
      holder.tvSex = (TextView)convertView.findViewById(R.id.mTv2);
      //将每个convertView对象中设置这个持有类对象
      convertView.setTag(holder);
    }
    //每次需要使用的时候都会拿到这个持有类
    holder = (ViewHolder)convertView.getTag();
    //然后可以直接使用这个类中的控件，对控件进行操作，而不用重复去findViewById了
    holder.tvName.setText(data.get(position).getName());
    holder.tvSex.setText(data.get(position).getSex());
    return convertView;
  }

  /**
   * 通过这个类来保存当前所有的控件id
   */
  static class ViewHolder{
    TextView tvName;
    TextView tvSex;
  }
}