[Android]ListView性能优化之视图缓存(续)
前言缓存
在上一篇ListView性能优化之视图缓存咱们讨论了Google I/O中的优化方法，在各个论坛发帖后获得了不错的反馈，诸如：使用ViewHolder技术Tag的问题，利用HashMap自行存储的方案等。这里结合新浪微博中主界面的作法及测试数据与你们进一步探讨。
性能优化
文章优化
[Android]ListView性能优化之视图缓存 [本文的上篇]
ui
[Android]ListView性能优化之视图缓存 [JavaEye讨论帖]
this
正文spa
1、新浪微博code
1.1 截图
1.2 反编译后相关代码
HomeListActivity
public
View getView(
int
paramInt, View paramView, ViewGroup paramViewGroup)
{
int i = -- paramInt;
int j = - 1 ;
if (i == j);
for (Object localObject1 = HomeListActivity. this .getReloadView(); ; localObject1 = HomeListActivity. this .getLoadMoreView())
{
label26: return localObject1;
int k = HomeListActivity. this .mList.size();
int l = paramInt;
int i1 = k;
if (l != i1)
break ;
}
boolean bool1 = true ;
boolean bool2 = null ;
String str1;
label110: Object localObject2;
if (StaticInfo.mUser == null )
{
List localList1 = HomeListActivity. this .mList;
int i2 = paramInt;
str1 = ((MBlog)localList1.get(i2)).uid;
List localList2 = HomeListActivity. this .mList;
int i3 = paramInt;
String str2 = ((MBlog)localList2.get(i3)).uid;
String str3 = str1;
if ( ! str2.equals(str3))
break label271;
int i4 = 1 ;
label156: if (paramView != null )
break label277;
HomeListActivity localHomeListActivity1 = HomeListActivity. this ;
ListView localListView1 = HomeListActivity. this .mLvHome;
List localList3 = HomeListActivity. this .mList;
int i5 = paramInt;
MBlog localMBlog1 = (MBlog)localList3.get(i5);
HomeListActivity localHomeListActivity2 = HomeListActivity. this ;
int i6 = paramInt;
boolean bool4 = localHomeListActivity2.isNewCommer(i6);
int i7 = HomeListActivity. this .mReadMode;
localObject2 = new MBlogListItemView(localHomeListActivity1, localListView1, localMBlog1, bool1, bool2, i4, bool4, i7);
}
while ( true )
{
localObject1 = localObject2;
break label26:
str1 = StaticInfo.mUser.uid;
break label110:
label271: boolean bool3 = null ;
break label156:
label277: localObject2 = paramView;
try
{
MainListItemView localMainListItemView = (MainListItemView)localObject2;
List localList4 = HomeListActivity. this .mList;
int i8 = paramInt;
Object localObject3 = localList4.get(i8);
HomeListActivity localHomeListActivity3 = HomeListActivity. this ;
int i9 = paramInt;
boolean bool5 = localHomeListActivity3.isNewCommer(i9);
int i10 = HomeListActivity. this .mReadMode;
boolean bool6 = bool1;
boolean bool7 = bool2;
localMainListItemView.update(localObject3, bool6, bool7, bool5, i10);
}
catch (Exception localException)
{
HomeListActivity localHomeListActivity4 = HomeListActivity. this ;
ListView localListView2 = HomeListActivity. this .mLvHome;
List localList5 = HomeListActivity. this .mList;
int i11 = paramInt;
MBlog localMBlog2 = (MBlog)localList5.get(i11);
HomeListActivity localHomeListActivity5 = HomeListActivity. this ;
int i12 = paramInt;
boolean bool8 = localHomeListActivity5.isNewCommer(i12);
int i13 = HomeListActivity. this .mReadMode;
localObject2 = new MBlogListItemView(localHomeListActivity4, localListView2, localMBlog2, bool1, bool2, bool3, bool8, i13);
}
}
}
{
int i = -- paramInt;
int j = - 1 ;
if (i == j);
for (Object localObject1 = HomeListActivity. this .getReloadView(); ; localObject1 = HomeListActivity. this .getLoadMoreView())
{
label26: return localObject1;
int k = HomeListActivity. this .mList.size();
int l = paramInt;
int i1 = k;
if (l != i1)
break ;
}
boolean bool1 = true ;
boolean bool2 = null ;
String str1;
label110: Object localObject2;
if (StaticInfo.mUser == null )
{
List localList1 = HomeListActivity. this .mList;
int i2 = paramInt;
str1 = ((MBlog)localList1.get(i2)).uid;
List localList2 = HomeListActivity. this .mList;
int i3 = paramInt;
String str2 = ((MBlog)localList2.get(i3)).uid;
String str3 = str1;
if ( ! str2.equals(str3))
break label271;
int i4 = 1 ;
label156: if (paramView != null )
break label277;
HomeListActivity localHomeListActivity1 = HomeListActivity. this ;
ListView localListView1 = HomeListActivity. this .mLvHome;
List localList3 = HomeListActivity. this .mList;
int i5 = paramInt;
MBlog localMBlog1 = (MBlog)localList3.get(i5);
HomeListActivity localHomeListActivity2 = HomeListActivity. this ;
int i6 = paramInt;
boolean bool4 = localHomeListActivity2.isNewCommer(i6);
int i7 = HomeListActivity. this .mReadMode;
localObject2 = new MBlogListItemView(localHomeListActivity1, localListView1, localMBlog1, bool1, bool2, i4, bool4, i7);
}
while ( true )
{
localObject1 = localObject2;
break label26:
str1 = StaticInfo.mUser.uid;
break label110:
label271: boolean bool3 = null ;
break label156:
label277: localObject2 = paramView;
try
{
MainListItemView localMainListItemView = (MainListItemView)localObject2;
List localList4 = HomeListActivity. this .mList;
int i8 = paramInt;
Object localObject3 = localList4.get(i8);
HomeListActivity localHomeListActivity3 = HomeListActivity. this ;
int i9 = paramInt;
boolean bool5 = localHomeListActivity3.isNewCommer(i9);
int i10 = HomeListActivity. this .mReadMode;
boolean bool6 = bool1;
boolean bool7 = bool2;
localMainListItemView.update(localObject3, bool6, bool7, bool5, i10);
}
catch (Exception localException)
{
HomeListActivity localHomeListActivity4 = HomeListActivity. this ;
ListView localListView2 = HomeListActivity. this .mLvHome;
List localList5 = HomeListActivity. this .mList;
int i11 = paramInt;
MBlog localMBlog2 = (MBlog)localList5.get(i11);
HomeListActivity localHomeListActivity5 = HomeListActivity. this ;
int i12 = paramInt;
boolean bool8 = localHomeListActivity5.isNewCommer(i12);
int i13 = HomeListActivity. this .mReadMode;
localObject2 = new MBlogListItemView(localHomeListActivity4, localListView2, localMBlog2, bool1, bool2, bool3, bool8, i13);
}
}
}
代码说明：
代码流程已经比较混乱，可是这里能看到并无直接的inflate，而是自定义了继承自LinearLayout的MBlogListItemView。
MBlogListItemView
public
MBlogListItemView(Context paramContext, ListView paramListView, MBlog paramMBlog,
boolean
paramBoolean1,
boolean
paramBoolean2,
boolean
paramBoolean3,
boolean
paramBoolean4,
int
paramInt)
{
super (paramContext);
this .context = paramContext;
this .parent = paramListView;
this .mBlog = paramMBlog;
String str1 = paramContext.getCacheDir().getAbsolutePath();
this .mCacheDir = str1;
String str2 = paramContext.getFilesDir().getAbsolutePath();
this .mFileDir = str2;
((LayoutInflater)paramContext.getSystemService( " layout_inflater " )).inflate( 2130903061 , this );
TextView localTextView1 = (TextView)findViewById( 2131624016 );
this .mName = localTextView1;
TextView localTextView2 = (TextView)findViewById( 2131624041 );
this .mDate = localTextView2;
TextView localTextView3 = (TextView)findViewById( 2131624018 );
this .mContent = localTextView3;
TextView localTextView4 = (TextView)findViewById( 2131624046 );
this .mSubContent = localTextView4;
ImageView localImageView1 = (ImageView)findViewById( 2131624040 );
this .mIconV = localImageView1;
ImageView localImageView2 = (ImageView)findViewById( 2131624042 );
this .mIconPic = localImageView2;
ImageView localImageView3 = (ImageView)findViewById( 2131624044 );
this .mUploadPic1 = localImageView3;
ImageView localImageView4 = (ImageView)findViewById( 2131623979 );
this .mUploadPic2 = localImageView4;
TextView localTextView5 = (TextView)findViewById( 2131624047 );
this .tvForm = localTextView5;
TextView localTextView6 = (TextView)findViewById( 2131623989 );
this .tvComment = localTextView6;
this .tvComment.setOnClickListener( this );
TextView localTextView7 = (TextView)findViewById( 2131623988 );
this .tvRedirect = localTextView7;
this .tvRedirect.setOnClickListener( this );
ImageView localImageView5 = (ImageView)findViewById( 2131624049 );
this .imComment = localImageView5;
this .imComment.setOnClickListener( this );
ImageView localImageView6 = (ImageView)findViewById( 2131624048 );
this .imRedirect = localImageView6;
this .imRedirect.setOnClickListener( this );
ImageView localImageView7 = (ImageView)findViewById( 2131624043 );
this .imGpsIcon = localImageView7;
ImageView localImageView8 = (ImageView)findViewById( 2131624013 );
this .mPortrait = localImageView8;
LinearLayout localLinearLayout = (LinearLayout)findViewById( 2131624045 );
this .mSubLayout = localLinearLayout;
this .mReadMode = paramInt;
MBlogListItemView localMBlogListItemView = this ;
MBlog localMBlog = paramMBlog;
boolean bool1 = paramBoolean1;
boolean bool2 = paramBoolean2;
boolean bool3 = paramBoolean4;
int i = paramInt;
localMBlogListItemView.update(localMBlog, bool1, bool2, bool3, i);
this .mUploadPic1.setOnClickListener( this );
this .mUploadPic2.setOnClickListener( this );
}
{
super (paramContext);
this .context = paramContext;
this .parent = paramListView;
this .mBlog = paramMBlog;
String str1 = paramContext.getCacheDir().getAbsolutePath();
this .mCacheDir = str1;
String str2 = paramContext.getFilesDir().getAbsolutePath();
this .mFileDir = str2;
((LayoutInflater)paramContext.getSystemService( " layout_inflater " )).inflate( 2130903061 , this );
TextView localTextView1 = (TextView)findViewById( 2131624016 );
this .mName = localTextView1;
TextView localTextView2 = (TextView)findViewById( 2131624041 );
this .mDate = localTextView2;
TextView localTextView3 = (TextView)findViewById( 2131624018 );
this .mContent = localTextView3;
TextView localTextView4 = (TextView)findViewById( 2131624046 );
this .mSubContent = localTextView4;
ImageView localImageView1 = (ImageView)findViewById( 2131624040 );
this .mIconV = localImageView1;
ImageView localImageView2 = (ImageView)findViewById( 2131624042 );
this .mIconPic = localImageView2;
ImageView localImageView3 = (ImageView)findViewById( 2131624044 );
this .mUploadPic1 = localImageView3;
ImageView localImageView4 = (ImageView)findViewById( 2131623979 );
this .mUploadPic2 = localImageView4;
TextView localTextView5 = (TextView)findViewById( 2131624047 );
this .tvForm = localTextView5;
TextView localTextView6 = (TextView)findViewById( 2131623989 );
this .tvComment = localTextView6;
this .tvComment.setOnClickListener( this );
TextView localTextView7 = (TextView)findViewById( 2131623988 );
this .tvRedirect = localTextView7;
this .tvRedirect.setOnClickListener( this );
ImageView localImageView5 = (ImageView)findViewById( 2131624049 );
this .imComment = localImageView5;
this .imComment.setOnClickListener( this );
ImageView localImageView6 = (ImageView)findViewById( 2131624048 );
this .imRedirect = localImageView6;
this .imRedirect.setOnClickListener( this );
ImageView localImageView7 = (ImageView)findViewById( 2131624043 );
this .imGpsIcon = localImageView7;
ImageView localImageView8 = (ImageView)findViewById( 2131624013 );
this .mPortrait = localImageView8;
LinearLayout localLinearLayout = (LinearLayout)findViewById( 2131624045 );
this .mSubLayout = localLinearLayout;
this .mReadMode = paramInt;
MBlogListItemView localMBlogListItemView = this ;
MBlog localMBlog = paramMBlog;
boolean bool1 = paramBoolean1;
boolean bool2 = paramBoolean2;
boolean bool3 = paramBoolean4;
int i = paramInt;
localMBlogListItemView.update(localMBlog, bool1, bool2, bool3, i);
this .mUploadPic1.setOnClickListener( this );
this .mUploadPic2.setOnClickListener( this );
}
代码说明：
a). MBlogListItemView extends LinearLayout implements MainListItemView
b).
inflate(
2130903061,this)这个数字表明R.layout.itemview。
2、测试方案（方案五）
按照新浪微博相似的作法进行测试。
2.1 测试代码
@Override
public View getView( int position, View convertView, ViewGroup parent) {
// 开始计时
long startTime = System.nanoTime();
TestItemLayout item;
if (convertView == null ) {
item = new TestItemLayout(BaseAdapterActivity. this );
} else
item = (TestItemLayout) convertView;
item.icon1.setImageResource(R.drawable.icon);
item.text1.setText(mData[position]);
item.icon2.setImageResource(R.drawable.icon);
item.text2.setText(mData[position]);
// 中止计时
long endTime = System.nanoTime();
// 计算耗时
long val = (endTime - startTime) / 1000L ;
Log.e( " Test " , " Position: " + position + " : " + val);
if (count < 100 ) {
if (val < 2000L ) {
sum += val;
count ++ ;
}
} else
mTV.setText(String.valueOf(sum / 100L ) + " : " + nullcount); // 显示统计结果
return item;
}
public View getView( int position, View convertView, ViewGroup parent) {
// 开始计时
long startTime = System.nanoTime();
TestItemLayout item;
if (convertView == null ) {
item = new TestItemLayout(BaseAdapterActivity. this );
} else
item = (TestItemLayout) convertView;
item.icon1.setImageResource(R.drawable.icon);
item.text1.setText(mData[position]);
item.icon2.setImageResource(R.drawable.icon);
item.text2.setText(mData[position]);
// 中止计时
long endTime = System.nanoTime();
// 计算耗时
long val = (endTime - startTime) / 1000L ;
Log.e( " Test " , " Position: " + position + " : " + val);
if (count < 100 ) {
if (val < 2000L ) {
sum += val;
count ++ ;
}
} else
mTV.setText(String.valueOf(sum / 100L ) + " : " + nullcount); // 显示统计结果
return item;
}
TestItemLayout
public
class
TestItemLayout
extends
LinearLayout {
public TextView text1;
public ImageView icon1;
public TextView text2;
public ImageView icon2;
public TestItemLayout(Context context) {
super (context);
((LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(
R.layout.list_item_icon_text, this );
icon1 = (ImageView) findViewById(R.id.icon1);
text1 = (TextView) findViewById(R.id.text1);
icon2 = (ImageView) findViewById(R.id.icon2);
text2 = (TextView) findViewById(R.id.text2);
}
}
public TextView text1;
public ImageView icon1;
public TextView text2;
public ImageView icon2;
public TestItemLayout(Context context) {
super (context);
((LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(
R.layout.list_item_icon_text, this );
icon1 = (ImageView) findViewById(R.id.icon1);
text1 = (TextView) findViewById(R.id.text1);
icon2 = (ImageView) findViewById(R.id.icon2);
text2 = (TextView) findViewById(R.id.text2);
}
}
2.2 测试结果
| 次数 |
4个子元素 |
10个子元素 |
| 第一次 |
347 |
460 |
| 第二次 |
310 |
477 |
| 第三次 |
324 |
508 |
| 第四次 |
339 |
492 |
| 第五次 |
341 |
465 |
3、总结
从测试结果来看与ViewHolder性能很是接近，不会出现tag图片变小的问题(关于图片变小的问题，有朋友说是TAG中的元素对大小和位置有记忆)，也能有效的减小findViewById的执行次数，这里建议彻底能够取代ViewHolder。
关于ListView内部Adapter的心得你们能够看一下上文的总结4.1。
4、考虑
关于静态内部类这里不是很理解，是否能应用方案五还有待验证。
5、后期维护
2011-4-29 来自Stony Wang关于Tag的解释：
结束
优化ListView不单单只有对convertView的优化，还有许多这样那样的技巧，欢迎你们交流与分享 :)
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