Android的 - 自定义列表视图滚动很慢 [英] Android - Custom Listview Scrolling is Very Slow

问题描述

我有一个ListView有时夸大一个XML（TextView的项目）或其它XML（TextView的+图像项）。我跟着这些指示，以获得更好的性能。

I've got a listview which sometimes inflate a XML (TextView Item) or another XML (TextView+Image Item). And i followed these instructions to get a better performance.

http://www.google。 COM /事件/ IO / 2010 /会话/世界-列表视图中，android.html

https://dl.google.com/ / Android的世界 - 列表视图 - android.pdf googleio / 2010

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

这是现在好，但仍无法获得最佳的性能，仍然滚动速度很慢。这是我的code：

It's now better, but still can't get best performance and still scroll is working slowly. Here's my code :

GetView：（// ViewHolder 0 - >部分项目 ViewHolder 1 - >参赛作品）

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

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：

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>

我需要的任何建议。谢谢你。

I need any suggestions. Thanks.

推荐答案

如果这个被接受，我想我需要包括这里的调试：

If this is accepted I think I need to include the debug here:

1. 删除 ellipsize 和 fadingedge ，并为双方的TextView设置宽度为 match_parent ，如果滚动仍然缓慢，尝试下。

1. Remove the ellipsize and fadingedge, and for both TextView set the width to match_parent, if scrolling still slow, try next.

scaleType =fitXY与 WRAP_CONTENT 上的ImageView实际上听起来挺，如果你问发生冲突我尝试专门设置的宽度和高度可能48dp或55dp，那么 fitXY 是有道理的。

scaleType="fitXY" together with wrap_content on ImageView actually sounds quite, conflicting if you ask me, try specifically setting the width and height to maybe 48dp or 55dp, then fitXY makes sense.

下面的函数来适当BaseAdapter类的例子：

Here's an example of functions to a proper BaseAdapter class:

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.
}

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