Java ListView在某些屏幕分辨率上的滚动性能
我编写了一些代码来加载JSON并在ListView中显示它(这部分工作正常),但我的问题是,当我尝试在某些设备上滚动ListView时,它出现了问题。特别是在Nexus S设备上,它工作得非常好,但我在其他设备(如Nexus 4、Nexus 7)上测试了它,并且在这些设备上,ListView具有不稳定的渲染延迟(当我尝试滚动它时) 在模拟器和480x800分辨率的设备上,它可以正常工作 布里格达普特:Java ListView在某些屏幕分辨率上的滚动性能,java,android,Java,Android,我编写了一些代码来加载JSON并在ListView中显示它(这部分工作正常),但我的问题是,当我尝试在某些设备上滚动ListView时,它出现了问题。特别是在Nexus S设备上,它工作得非常好,但我在其他设备(如Nexus 4、Nexus 7)上测试了它,并且在这些设备上,ListView具有不稳定的渲染延迟(当我尝试滚动它时) 在模拟器和480x800分辨率的设备上,它可以正常工作 布里格达普特: package com.brige.adapter; import java.util.Ar
package com.brige.adapter;
import java.util.ArrayList;
import java.util.HashMap;
import com.brige.MainActivity;
import com.brige.R;
import com.brige.json.ImageLoader;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class BRIgeAdapter extends BaseAdapter {
private LayoutInflater inflater;
private Activity activity;
private ArrayList<HashMap<String, String>> data;
public ImageLoader imageLoader;
HashMap<String, String> itemList;
public BRIgeAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data = d;
inflater = (LayoutInflater) activity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader = new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return null;
}
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
holder = new ViewHolder();
convertView = inflater.inflate(R.layout.list_row, parent, false);
holder.journal = (TextView) convertView
.findViewById(R.id.smalljournal);
holder.thumb_image = (ImageView) convertView
.findViewById(R.id.smallthumb);
holder.title = (TextView) convertView.findViewById(R.id.smalltitle);
holder.description = (TextView) convertView
.findViewById(R.id.smalldesc);
holder.statId = (TextView) convertView
.findViewById(R.id.smallstatID);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
itemList = data.get(position);
if (itemList != null) {
holder.journal.setText(itemList.get(MainActivity.KEY_journal));
holder.statId.setText(itemList.get(MainActivity.KEY_statID));
holder.journal.setTypeface(MainActivity.tf2);
String titleString = itemList.get(MainActivity.KEY_title);
holder.title.setText(titleString);
holder.title.setTypeface(MainActivity.tf2);
holder.description.setText(itemList
.get(MainActivity.KEY_description));
holder.description.setTypeface(MainActivity.tf2);
imageLoader.DisplayImage(itemList.get(MainActivity.KEY_image),
holder.thumb_image);
}
return convertView;
}
static class ViewHolder {
TextView journal, title, description, statId;
ImageView thumb_image;
}
}
包com.brige.adapter;
导入java.util.ArrayList;
导入java.util.HashMap;
导入com.brige.main活动;
进口大桥;
导入com.brige.json.ImageLoader;
导入android.app.Activity;
导入android.content.Context;
导入android.view.LayoutInflater;
导入android.view.view;
导入android.view.ViewGroup;
导入android.widget.BaseAdapter;
导入android.widget.ImageView;
导入android.widget.TextView;
公共类BRIgeAdapter扩展了BaseAdapter{
私人充气机;
私人活动;
私有数组列表数据;
公共图像加载器;
HashMap项目列表;
公共BRIgeAdapter(活动a,阵列列表d){
活动=a;
数据=d;
充气器=(充气器)活动
.getSystemService(上下文布局\充气机\服务);
imageLoader=新的imageLoader(activity.getApplicationContext());
}
public int getCount(){
返回data.size();
}
公共对象getItem(int位置){
返回null;
}
公共长getItemId(int位置){
返回0;
}
@凌驾
公共视图getView(int位置、视图转换视图、视图组父视图){
视窗座;
if(convertView==null){
holder=新的ViewHolder();
convertView=充气机。充气(R.layout.list_行,父项,false);
holder.journal=(TextView)convertView
.findviewbyd(R.id.smalljournal);
holder.thumb_image=(ImageView)convertView
.findviewbyd(R.id.smallthumb);
holder.title=(TextView)convertView.findViewById(R.id.smalltitle);
holder.description=(TextView)convertView
.findviewbyd(R.id.smalldesc);
holder.statId=(TextView)convertView
.findviewbyd(R.id.smallstatID);
convertView.setTag(支架);
}否则{
holder=(ViewHolder)convertView.getTag();
}
itemList=data.get(位置);
if(itemList!=null){
holder.journal.setText(itemList.get(MainActivity.KEY_journal));
holder.statId.setText(itemList.get(MainActivity.KEY_statId));
holder.journal.setTypeface(MainActivity.tf2);
String titleString=itemList.get(MainActivity.KEY\u title);
holder.title.setText(标题串);
holder.title.setTypeface(MainActivity.tf2);
holder.description.setText(项目列表
.get(MainActivity.KEY_description));
holder.description.setTypeface(MainActivity.tf2);
imageLoader.DisplayImage(itemList.get(MainActivity.KEY_image)),
夹持器(拇指图像);
}
返回视图;
}
静态类视窗夹{
TextView日志、标题、说明、statId;
ImageView拇指图像;
}
}
图像加载器:
package com.brige.json;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import com.brige.R;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.widget.ImageView;
public class ImageLoader {
MemoryCache memoryCache = new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews = Collections
.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;
public ImageLoader(Context context) {
fileCache = new FileCache(context);
executorService = Executors.newFixedThreadPool(5);
}
final int stub_id = R.drawable.aaaaaaaaaaaaaaa;
public void DisplayImage(String url, ImageView imageView) {
imageViews.put(imageView, url);
Bitmap bitmap = memoryCache.get(url);
if (bitmap != null)
imageView.setImageBitmap(bitmap);
else {
queuePhoto(url, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, ImageView imageView) {
PhotoToLoad p = new PhotoToLoad(url, imageView);
executorService.submit(new PhotosLoader(p));
}
private Bitmap getBitmap(String url) {
File f = fileCache.getFile(url);
// from SD cache
Bitmap b = decodeFile(f);
if (b != null)
return b;
// from web
try {
Bitmap bitmap = null;
URL imageUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection) imageUrl
.openConnection();
conn.setConnectTimeout(30000);
conn.setReadTimeout(30000);
conn.setInstanceFollowRedirects(true);
InputStream is = conn.getInputStream();
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Throwable ex) {
ex.printStackTrace();
if (ex instanceof OutOfMemoryError)
memoryCache.clear();
return null;
}
}
// decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f) {
try {
// decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
FileInputStream stream1 = new FileInputStream(f);
BitmapFactory.decodeStream(stream1, null, o);
stream1.close();
// Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE = 70;
int width_tmp = o.outWidth, height_tmp = o.outHeight;
int scale = 1;
while (true) {
if (width_tmp / 2 < REQUIRED_SIZE
|| height_tmp / 2 < REQUIRED_SIZE)
break;
width_tmp /= 2;
height_tmp /= 2;
scale *= 2;
}
// decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
FileInputStream stream2 = new FileInputStream(f);
Bitmap bitmap = BitmapFactory.decodeStream(stream2, null, o2);
stream2.close();
return bitmap;
} catch (FileNotFoundException e) {
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
// Task for the queue
private class PhotoToLoad {
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i) {
url = u;
imageView = i;
}
}
class PhotosLoader implements Runnable {
PhotoToLoad photoToLoad;
PhotosLoader(PhotoToLoad photoToLoad) {
this.photoToLoad = photoToLoad;
}
@Override
public void run() {
try {
if (imageViewReused(photoToLoad))
return;
Bitmap bmp = getBitmap(photoToLoad.url);
memoryCache.put(photoToLoad.url, bmp);
if (imageViewReused(photoToLoad))
return;
BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad);
Activity a = (Activity) photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
} catch (Throwable th) {
th.printStackTrace();
}
}
}
boolean imageViewReused(PhotoToLoad photoToLoad) {
String tag = imageViews.get(photoToLoad.imageView);
if (tag == null || !tag.equals(photoToLoad.url))
return true;
return false;
}
// Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable {
Bitmap bitmap;
PhotoToLoad photoToLoad;
public BitmapDisplayer(Bitmap b, PhotoToLoad p) {
bitmap = b;
photoToLoad = p;
}
public void run() {
if (imageViewReused(photoToLoad))
return;
if (bitmap != null)
photoToLoad.imageView.setImageBitmap(bitmap);
else
photoToLoad.imageView.setImageResource(stub_id);
}
}
public void clearCache() {
memoryCache.clear();
fileCache.clear();
}
}
package com.brige.json;
导入java.io.File;
导入java.io.FileInputStream;
导入java.io.FileNotFoundException;
导入java.io.FileOutputStream;
导入java.io.IOException;
导入java.io.InputStream;
导入java.io.OutputStream;
导入java.net.HttpURLConnection;
导入java.net.URL;
导入java.util.Collections;
导入java.util.Map;
导入java.util.WeakHashMap;
导入java.util.concurrent.ExecutorService;
导入java.util.concurrent.Executors;
进口大桥;
导入android.app.Activity;
导入android.content.Context;
导入android.graphics.Bitmap;
导入android.graphics.BitmapFactory;
导入android.widget.ImageView;
公共类图像加载器{
MemoryCache MemoryCache=新的MemoryCache();
文件缓存文件缓存;
私有地图图像视图=集合
.synchronizedMap(新WeakHashMap());
执行服务执行服务;
公共图像加载器(上下文){
fileCache=新的fileCache(上下文);
executorService=Executors.newFixedThreadPool(5);
}
最终int存根_id=R.drawable.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;
public void DisplayImage(字符串url,ImageView){
put(imageView,url);
位图位图=memoryCache.get(url);
if(位图!=null)
设置图像位图(位图);
否则{
队列照片(url、imageView);
setImageResource(存根id);
}
}
私有void队列照片(字符串url,ImageView){
PhotoToLoad p=新的PhotoToLoad(url,imageView);
executorService.submit(新的PhotoLoader(p));
}
私有位图getBitmap(字符串url){
文件f=fileCache.getFile(url);
//从SD缓存
位图b=解码文件(f);
如果(b!=null)
返回b;
//从网络
试一试{
位图=空;
URL imageUrl=新URL(URL);
HttpURLConnection conn=(HttpURLConnection)imageUrl
.openConnection();
连接设置连接超时(30000);
连接设置读取超时(30000);
conn.setInstanceFollowRedirects(真);
InputStream is=conn.getInputStream();
OutputStream os=新文件OutputStream(f);
Utils.CopyStream(is,os);
os.close();
位图=解码文件(f);
返回位图;
}捕获(可丢弃的ex){
例如printStackTrace();
if(ex instanceof OutOfMemoryError)
memoryCache.clear();
返回n