Question

我有部分列表，但这个ListView非常慢。

我需要任何持有人，但我不知道我是如何做到的。

当我有一种类型的视图时，它很简单，但在这里我有问题。

我创建了holder，但是当ListView显示时，我看到了：

“影片名称”， “标题”， “标题”， “项目”， “项目”

“影片名称”， “标题”， “标题”， “项目”

“影片名称”， “标题”， “标题”， “项目”， “项目”， “项目”

这是我的代码：

public class EntryAdapter extends ArrayAdapter<Item> {

private ArrayList<Item> items;
private LayoutInflater vi;
Context context;
private String nazwa;

public EntryAdapter(Context context,ArrayList<Item> items, String nazwa) {
    super(context,0, items);
    this.items = items;
    this.context = context;
    this.nazwa = nazwa;
    vi = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

我得到了视图：

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

    final Item i = items.get(position);
    if (i != null) {
        if(i.isSection()){
            SectionItem si = (SectionItem)i;
            convertView = vi.inflate(R.layout.list_item_section, null);

            convertView.setOnClickListener(null);
            convertView.setOnLongClickListener(null);
            convertView.setLongClickable(false);

            final TextView sectionView = (TextView) convertView.findViewById(R.id.list_item_section_text);
        }else{
                Obiekt ei = (Obiekt)i;
                convertView = vi.inflate(R.layout.row_list, null);
                final TextView title = (TextView)convertView.findViewById(R.id.row_tytul);
                final TextView odleglosc = (TextView)convertView.findViewById(R.id.row_odleglosc);
                final ImageView obrazek = (ImageView)convertView.findViewById(R.id.row_ikona_mala);
                final LinearLayout pole = (LinearLayout)convertView.findViewById(R.id.LinearLayout1);

        }
    }
    return convertView;
}

Answer 1

我有部分列表，但这个ListView非常慢。

您总是在getView（）方法中为新视图充气。通知视图通常需要很长时间。

您想通过检查'convertView'是否为null来重复使用以前的视图。这将提高性能。请注意，您还必须实施getItemViewType()和getViewTypeCount()，因为您有两种不同的观点：

public class MyAdapter extends ArrayAdapter<Item> {

    private List<Item> items;
    private int TYPE_SECTION = 0;
    private int TYPE_OBIEKT = 1;
    private static LayoutInflater vi;

    public MyAdapter(Context context, List<Item> _items) {
        super(context, 0);
        vi = (LayoutInflater) context.getSystemService(Service.LAYOUT_INFLATER_SERVICE);
        items = _items;
    }

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


    /**
     * @see android.widget.BaseAdapter#getViewTypeCount()
     * Determines how many different views you have
     */
    @Override
    public int getViewTypeCount() {
        return 2; // We have two different kinds of views
    }

    /**
     * @see android.widget.BaseAdapter#getItemViewType(int)
     */
    @Override
    public int getItemViewType(int position) {
        Item item = items.get(position);
        if (item.isSection())
            return TYPE_SECTION;

        return TYPE_OBIEKT;
    }

    /**
     * @see android.widget.ArrayAdapter#getView(int, android.view.View, android.view.ViewGroup)
     */
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        // Get the item
        final Item item = items.get(position);

        if (getItemViewType(position) == TYPE_SECTION) {

            // Return a SectionView object
            return getSectionView(position, convertView, parent, (SectionItem) item);
        }

        // Return an Obiekt object
        return getObiektView(position, convertView, parent, (Obiekt) item);
    }

    /**
     * SectionView specific
     * 
     * @param position
     * @param convertView
     * @param parent
     * @param item
     * @return
     */
    public View getSectionView(int position, View convertView, ViewGroup parent, SectionItem item) {

        SectionHolder holder;
        if(convertView == null){

            holder = new SectionHolder();

            // Inflate a new View
            convertView = vi.inflate(R.layout.list_item_section, null);
            holder.sectionView = (TextView) convertView.findViewById(R.id.list_item_section_text);

            // Set the ObiektHolder as the tag, to retrieve it for re-using
            convertView.setTag(holder);

        } else {
            holder = (SectionHolder) convertView.getTag();
        }

        // Holder is never null here
        holder.sectionView.setText(item.getSectionTitle());

        return convertView;

    }

    public View getObiektView(int position, View convertView, ViewGroup parent, Obiekt item) {

        ObiektHolder holder;
        if(convertView == null){

            holder = new ObiektHolder();

            // Inflate a new View
            convertView = vi.inflate(R.layout.row_list, null);
            holder.title = (TextView)convertView.findViewById(R.id.row_tytul);
            holder.odleglosc = (TextView)convertView.findViewById(R.id.row_odleglosc);
            holder.obrazek = (ImageView)convertView.findViewById(R.id.row_ikona_mala);
            holder.pole = (LinearLayout)convertView.findViewById(R.id.LinearLayout1);

            // Set the ObiektHolder as the tag, to retrieve it for re-using
            convertView.setTag(holder);

        } else {
            holder = (ObiektHolder) convertView.getTag();
        }

        // Holder is never null here
        holder.title.setText(item.getObiektTitle());

        return convertView;
    }

    private static class SectionHolder {
        TextView    sectionView;
    }

    private static class ObiektHolder {
        TextView        title;
        TextView        odleglosc;
        ImageView       obrazek;
        LinearLayout    pole;
    }
}

注意：现在测试并正常工作！

Answer 2

http://www.youtube.com/watch?v=wDBM6wVEO70。与视图持有者讨论listview的性能。

http://developer.android.com/training/improving-layouts/smooth-scrolling.html。请查看标题在视图持有者中保持视图对象

下的链接中的文档

直接来自文档：

在滚动ListView期间，您的代码可能经常调用findViewById（），这会降低性能。即使适配器返回一个膨胀的视图以进行回收，您仍然需要查找元素并更新它们。重复使用findViewById（）的方法是使用“视图持有者”设计模式。

观察者的例子。

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {
  // TODO Auto-generated method stub
   ViewHolder holder;

        if (convertView == null) {
                  convertView = mInflater.inflate(R.layout.list, null);
                  convertView.setLayoutParams(new AbsListView.LayoutParams(LayoutParams.FILL_PARENT,
                          LayoutParams.WRAP_CONTENT));
                  // Creates a ViewHolder and store references to the two children views
                  // we want to bind data to.
                  holder = new ViewHolder();
                  holder.t1=(TextView) convertView.findViewById(R.id.textView1);
                  holder.t2 = (TextView) convertView.findViewById(R.id.textView2);
                  holder.t3 = (TextView) convertView.findViewById(R.id.textView3);

                  convertView.setTag(holder);
              } else {
                  // Get the ViewHolder back to get fast access to the TextView

                  holder = (ViewHolder) convertView.getTag();
              }
              holder.t1.setText("set text")
              holder.t2.setText("set text2");
              holder.t3.setText("set text3");
              return convertView;
  }
}


class ViewHolder
{
  TextView t1,t2,t3;
}

Answer 3

首先，你必须检查convertView是否已经膨胀。如果它已经充气，你可以回收它，你不必再次充气。这就是你获得表现的地方。

示例：

public View getView(int position, View convertView, ViewGroup parent) { View itemView = null; // not inflated if (convertView == null) { LayoutInflater inflater = (LayoutInflater) parent.getContext() .getSystemService(Context.LAYOUT_INFLATER_SERVICE); itemView = inflater.inflate(R.layout.list_item_section, null); } // already inflated else { itemView = convertView; } // get your textview's etc. return itemView; }

Android SecionList和Holder

3 个答案: