android - Android - 自定义列表视图滚动非常慢

Question

我有一个列表视图，它有时会膨胀 XML（TextView 项）或另一个 XML（TextView+Image 项）。我按照这些说明获得了更好的性能。

http://www.google.com/events/io/2010/sessions/world-of-listview-android.html

https://dl.google.com/googleio/2010/android-world-of-listview-android.pdf

http://android.amberfog.com/?p=296

现在好多了，但仍然无法获得最佳性能，并且滚动仍然运行缓慢。这是我的代码：

GetView : (//ViewHolder 0 -> Section Item ViewHolder 1 -> Entry Item)

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        ViewHolder[] viewHolders=new ViewHolder[2];
        final ListItems.Item i = items.get(position);
        if (i != null) {
            if(i.isSection()){
                TextView sectionView;
                ListItems.SectionItem si = (ListItems.SectionItem)i;
                if (v==null || ((ViewHolder[])v.getTag())==null || ((ViewHolder[])v.getTag())[0]==null)
                {
                    v = vi.inflate(R.layout.order_list_item_section, null);
                    sectionView= (TextView) v.findViewById(R.id.list_item_section_text);
                    viewHolders[0]=new ViewHolder();
                    viewHolders[0].Title=sectionView;
                    v.setTag(viewHolders);
                }
                else
                {
                    viewHolders[0]=((ViewHolder[]) v.getTag())[0];
                    sectionView=viewHolders[0].Title;
                }
                sectionView.setBackgroundColor(android.graphics.Color.BLACK);
                sectionView.setText(si.getTitle());
            }
            else if(i.isEntryItem())
            {               
                ListItems.EntryItem ei = (ListItems.EntryItem)i;
                TextView title = null,subtitle = null;
                ImageView img = null;
                if (v==null || ((ViewHolder[])v.getTag())==null || ((ViewHolder[])v.getTag())[1]==null)
                {
                    v = vi.inflate(R.layout.order_list_item_entry, null);
                    title = (TextView)v.findViewById(R.id.list_item_entry_title);
                    img=(ImageView)v.findViewById(R.id.list_item_entry_drawable);
                    subtitle = (TextView)v.findViewById(R.id.list_item_entry_summary);
                    viewHolders[1]=new ViewHolder();
                    viewHolders[1].Title=title;
                    viewHolders[1].SubTitle=subtitle;
                    viewHolders[1].TableImage=img;
                    v.setTag(viewHolders);
                }
                else
                {
                    viewHolders[1]=((ViewHolder[]) v.getTag())[1];
                    title=viewHolders[1].Title;
                    subtitle=viewHolders[1].SubTitle;
                    img=viewHolders[1].TableImage;
                }
                title.setTextSize(20);
                title.setTextColor(android.graphics.Color.BLACK);
                title.setText(Html.fromHtml("<b><i>"+ei.title+"</b></i>"));
                img.setImageBitmap(ei.tableImage);  
                img.setScaleType(ScaleType.FIT_XY);
                img.setAdjustViewBounds(true);
                if(!ei.subtitle.equals(""))
                {
                    subtitle.setTextSize(15);
                    subtitle.setTextColor(android.graphics.Color.GRAY);
                    subtitle.setText(Html.fromHtml("<i>"+ei.subtitle+"</i>"));
                }
            }

ViewHolder : 

    static class ViewHolder {
          TextView Title;
          TextView SubTitle;
          ImageView TableImage;
         }

编辑：

order_list_item_section.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <include
        android:id="@+id/list_item_section_text"
        layout="@android:layout/preference_category" />

</LinearLayout>

order_list_item_entry.xml ：

<?xml version="1.0" encoding="utf-8"?>

  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:minHeight="?android:attr/listPreferredItemHeight"
    android:gravity="center_vertical"
    android:paddingRight="?android:attr/scrollbarSize"
    android:background="#ffffff">

    <ImageView
        android:id="@+id/list_item_entry_drawable"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingLeft="6dp"/>

    <RelativeLayout
        android:layout_width="0dip"
        android:layout_height="wrap_content"
        android:layout_marginLeft="0dip"
        android:layout_marginRight="6dip"
        android:layout_marginTop="6dip"
        android:layout_marginBottom="6dip"
        android:layout_weight="1">

        <TextView android:id="@+id/list_item_entry_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:singleLine="true"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:ellipsize="marquee"
            android:fadingEdge="horizontal" />

        <TextView android:id="@+id/list_item_entry_summary"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/list_item_entry_title"
            android:layout_alignLeft="@id/list_item_entry_title"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:singleLine="true"
            android:textColor="?android:attr/textColorSecondary" /> 

    </RelativeLayout>

</LinearLayout>

我需要任何建议。谢谢。

score 2 · Accepted Answer

如果这被接受，我认为我需要在此处包含调试：

删除ellipsizeand fadingedge，并将两个 TextView 的宽度设置为match_parent，如果滚动仍然很慢，请尝试下一步。
scaleType="fitXY"加上wrap_contenton ImageView 实际上听起来很矛盾，如果您问我，请尝试将宽度和高度专门设置为 48dp 或 55dp，然后fitXY才有意义。

这是正确 BaseAdapter 类的函数示例：

public static final int SECTION = 2;
public static final int ENTRY_ITEM = 1;
private List<ListItems.Item> items; // I believe you have this List declared?

public YourClassConstructor(){
    //Whatever you need to accept and assign, probably the list itself.
}

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

public Object getItem(int position) {
    return items.get(position);
}

public long getItemId(int position) {
    return (long) position; // Or anything that can define your item
}

@Override
public int getViewTypeCount() {
    return 2; // 2 because you have Section and EntryItem
}

@Override
public int getItemViewType(int position) {
    int itemViewType;
    ListItems.Item i = items.get(position);

    if(i.isSection()){
        itemViewType = SECTION;
    }else{
        itemViewType = ENTRY_ITEM;
    }

    return itemViewType;
}

@Override
public View getView(final int position, final View convertView, final ViewGroup parent {
    //Here your convertView will always be the one you need, either as a section or entry_item
    //Unless there is no convertView available yet.
    //So your (ViewHolder[])v.getTag())[0/1] will less likely be null.
}

score 0 · Accepted Answer

v = vi.inflate(R.layout.order_list_item_section, null); 仅当 v 为空时才执行。这将有很大帮助。

android - Android - 自定义列表视图滚动非常慢

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