Android先进先出懒散加载
参考费多在讨论的懒散加载方法 我想知道,在显示从web下载的图像时,是否可以将以下代码从后进先出(LIFO)更改为先进先出(FIFO) 公共类图像加载器{Android先进先出懒散加载,android,lazy-loading,fifo,Android,Lazy Loading,Fifo,参考费多在讨论的懒散加载方法 我想知道,在显示从web下载的图像时,是否可以将以下代码从后进先出(LIFO)更改为先进先出(FIFO) 公共类图像加载器{ //the simplest in-memory cache implementation. This should be replaced with something like SoftReference or BitmapOptions.inPurgeable(since 1.6) private HashMap<String,
//the simplest in-memory cache implementation. This should be replaced with something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
private HashMap<String, Bitmap> cache=new HashMap<String, Bitmap>();
private File cacheDir;
public ImageLoader(Context context){
photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
//Find the dir to save cached images
if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"More");
else
cacheDir=context.getCacheDir();
if(!cacheDir.exists())
cacheDir.mkdirs();
}
final int stub_id=R.drawable.stub;
public void DisplayImage(String url, Activity activity, ImageView imageView)
{
if(cache.containsKey(url))
{
imageView.setImageBitmap(cache.get(url));
}
else
{
queuePhoto(url, activity, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, Activity activity, ImageView imageView)
{
//This ImageView may be used for other images before. So there may be some old tasks in the queue. We need to discard them.
photosQueue.Clean(imageView);
PhotoToLoad p=new PhotoToLoad(url, imageView);
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.push(p);
photosQueue.photosToLoad.notifyAll();
}
//start thread if it's not started yet
if(photoLoaderThread.getState()==Thread.State.NEW)
photoLoaderThread.start();
}
private Bitmap getBitmap(String url)
{
//I identify images by hashcode. Not a perfect solution, good for the demo.
String filename=String.valueOf(url.hashCode());
File f=new File(cacheDir, filename);
//from SD cache
Bitmap b = decodeFile(f);
if(b!=null)
return b;
//from web
try {
Bitmap bitmap=null;
InputStream instream = null;
HttpGet httpRequest = new HttpGet(new URI(url));
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response = (HttpResponse) httpclient.execute(httpRequest);
HttpEntity entity = response.getEntity();
BufferedHttpEntity bufHttpEntity = new BufferedHttpEntity(entity);
try
{
instream = bufHttpEntity.getContent();
} catch (Exception e)
{
} finally
{
if (instream != null)
{
instream.close();
}
}
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(instream, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex){
ex.printStackTrace();
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;
BitmapFactory.decodeStream(new FileInputStream(f),null,o);
//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;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {}
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;
}
}
PhotosQueue photosQueue=new PhotosQueue();
public void stopThread()
{
photoLoaderThread.interrupt();
}
//stores list of photos to download
class PhotosQueue
{
private Stack<PhotoToLoad> photosToLoad=new Stack<PhotoToLoad>();
//removes all instances of this ImageView
public void Clean(ImageView image)
{
for(int j=0 ;j<photosToLoad.size();){
if(photosToLoad.get(j).imageView==image)
photosToLoad.remove(j);
else
++j;
}
}
}
class PhotosLoader extends Thread {
public void run() {
try {
while(true)
{
//thread waits until there are any images to load in the queue
if(photosQueue.photosToLoad.size()==0)
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.wait();
}
if(photosQueue.photosToLoad.size()!=0)
{
PhotoToLoad photoToLoad;
synchronized(photosQueue.photosToLoad){
photoToLoad=photosQueue.photosToLoad.pop();
}
Bitmap bmp=getBitmap(photoToLoad.url);
cache.put(photoToLoad.url, bmp);
Object tag=photoToLoad.imageView.getTag();
if(tag!=null && ((String)tag).equals(photoToLoad.url)){
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad.imageView);
Activity a=(Activity)photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
if(Thread.interrupted())
break;
}
} catch (InterruptedException e) {
//allow thread to exit
}
}
}
PhotosLoader photoLoaderThread=new PhotosLoader();
//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
ImageView imageView;
public BitmapDisplayer(Bitmap b, ImageView i){bitmap=b;imageView=i;}
public void run()
{
if(bitmap!=null)
imageView.setImageBitmap(bitmap);
else
imageView.setImageResource(stub_id);
}
}
public void clearCache() {
//clear memory cache
cache.clear();
//clear SD cache
File[] files=cacheDir.listFiles();
for(File f:files)
f.delete();
}
//最简单的内存缓存实现。应该用SoftReference或BitmapOptions.inpurgable(自1.6起)之类的东西来代替它
私有HashMap缓存=新建HashMap();
私有文件cacheDir;
公共图像加载器(上下文){
photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
//查找目录以保存缓存的图像
if(android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_-MOUNTED))
cacheDir=新文件(android.os.Environment.getExternalStorageDirectory(),“更多”);
其他的
cacheDir=context.getCacheDir();
如果(!cacheDir.exists())
cacheDir.mkdirs();
}
最终int stub_id=R.drawable.stub;
public void DisplayImage(字符串url、活动活动、图像视图)
{
if(cache.containsKey(url))
{
setImageBitmap(cache.get(url));
}
其他的
{
队列照片(url、活动、图像视图);
setImageResource(存根id);
}
}
私有void queuePhoto(字符串url、活动活动、ImageView ImageView)
{
//此ImageView以前可能用于其他图像。因此队列中可能有一些旧任务。我们需要丢弃它们。
Photosque.Clean(imageView);
PhotoToLoad p=新的PhotoToLoad(url,imageView);
已同步(PhotoQueue.photosToLoad){
photoqueue.photoload.push(p);
photoqueue.phototoload.notifyAll();
}
//如果尚未启动,则启动线程
if(photoLoaderThread.getState()==Thread.State.NEW)
photoLoaderThread.start();
}
私有位图getBitmap(字符串url)
{
//我用hashcode识别图像。这不是一个完美的解决方案,适合演示。
String filename=String.valueOf(url.hashCode());
文件f=新文件(cacheDir,文件名);
//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;
InputStream instream=null;
HttpGet-httpRequest=newhttpget(新URI(url));
HttpClient HttpClient=新的DefaultHttpClient();
HttpResponse response=(HttpResponse)httpclient.execute(httpRequest);
HttpEntity=response.getEntity();
BufferedHttpEntity bufHttpEntity=新的BufferedHttpEntity(实体);
尝试
{
instream=bufhttpenty.getContent();
}捕获(例外e)
{
}最后
{
如果(流内!=null)
{
流内关闭();
}
}
OutputStream os=新文件OutputStream(f);
Utils.copyream(流内、操作系统);
os.close();
位图=解码文件(f);
返回位图;
}捕获(例外情况除外){
例如printStackTrace();
返回null;
}
}
//对图像进行解码和缩放以减少内存消耗
私有位图解码文件(文件f){
试一试{
//解码图像大小
BitmapFactory.Options o=新的BitmapFactory.Options();
o、 inJustDecodeBounds=true;
解码流(新的FileInputStream(f),null,o);
//找到正确的刻度值。它应该是2的幂。
所需的最终int_尺寸=70;
内部宽度=o.向外宽度,高度=o.向外高度;
int标度=1;
while(true){
如果(宽度)tmp/2堆栈本质上是后进先出的,那么您可能需要:
- 在对象引用PhotoToLoad上将堆栈更改为LinkedList
- 将PhotoToLoad中的push()替换为addFirst()
同步块
- 调用getFirst()并在第三个函数中替换pop(),然后再调用removeFirst()
同步块
请用这个ImageLoader类替换你的ImageLoader类。我测试了代码,它以FIFO顺序工作
public class ImageLoader {
MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
public ImageLoader(Context context){
//Make the background thead low priority. This way it will not affect the UI performance
photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
fileCache=new FileCache(context);
}
final int stub_id=R.drawable.stub;
public void DisplayImage(String url, Activity activity, ImageView imageView)
{
imageViews.put(imageView, url);
Bitmap bitmap=memoryCache.get(url);
if(bitmap!=null)
imageView.setImageBitmap(bitmap);
else
{
queuePhoto(url, activity, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, Activity activity, ImageView imageView)
{
//This ImageView may be used for other images before. So there may be some old tasks in the queue. We need to discard them.
photosQueue.Clean(imageView);
PhotoToLoad p=new PhotoToLoad(url, imageView);
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.add(p);
photosQueue.photosToLoad.notifyAll();
}
//start thread if it's not started yet
if(photoLoaderThread.getState()==Thread.State.NEW)
photoLoaderThread.start();
}
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);
InputStream is=conn.getInputStream();
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex){
ex.printStackTrace();
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;
BitmapFactory.decodeStream(new FileInputStream(f),null,o);
//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;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {}
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;
}
}
PhotosQueue photosQueue=new PhotosQueue();
public void stopThread()
{
photoLoaderThread.interrupt();
}
//stores list of photos to download
class PhotosQueue
{
private Queue<PhotoToLoad> photosToLoad=new LinkedList<PhotoToLoad>();
//removes all instances of this ImageView
public void Clean(ImageView image)
{
for(int j=0 ;j<photosToLoad.size();){
if(photosToLoad.element().imageView==image)
photosToLoad.remove(j);
else
++j;
}
}
}
class PhotosLoader extends Thread {
public void run() {
try {
while(true)
{
//thread waits until there are any images to load in the queue
if(photosQueue.photosToLoad.size()==0)
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.wait();
}
if(photosQueue.photosToLoad.size()!=0)
{
PhotoToLoad photoToLoad;
synchronized(photosQueue.photosToLoad){
photoToLoad=photosQueue.photosToLoad.poll();
}
Bitmap bmp=getBitmap(photoToLoad.url);
memoryCache.put(photoToLoad.url, bmp);
String tag=imageViews.get(photoToLoad.imageView);
if(tag!=null && tag.equals(photoToLoad.url)){
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad.imageView);
Activity a=(Activity)photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
if(Thread.interrupted())
break;
}
} catch (InterruptedException e) {
//allow thread to exit
}
}
}
PhotosLoader photoLoaderThread=new PhotosLoader();
//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
ImageView imageView;
public BitmapDisplayer(Bitmap b, ImageView i){bitmap=b;imageView=i;}
public void run()
{
if(bitmap!=null)
imageView.setImageBitmap(bitmap);
else
imageView.setImageResource(stub_id);
}
}
public void clearCache() {
memoryCache.clear();
fileCache.clear();
}
}
公共类ImageLoader{
MemoryCache MemoryCache=新的MemoryCache();
文件缓存文件缓存;
private Map ImageView=Collections.synchronizedMap(新的WeakHashMap());
公共图像加载器(上下文){
//将后台设为低优先级。这样不会影响UI性能
photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
fileCache=新的fileCache(上下文);
}
最终int stub_id=R.drawable.stub;
public void DisplayImage(字符串url、活动活动、图像视图)
{
put(imageView,url);
位图位图=memoryCache.get(url);
if(位图!=null)
设置图像位图(位图);
其他的
{
队列照片(url、活动、图像视图);
setImageResource(存根id);
}
}
私有void queuePhoto(字符串url、活动活动、ImageView ImageView)
{
//此ImageView以前可能用于其他图像。因此队列中可能有一些旧任务。我们需要丢弃它们。
Photosque.Clean(imageView);
PhotoToLoad p=新的PhotoToLoad(url,imageView);
已同步(PhotoQueue.photosToLoad){
photosque.phototoload.add(p);
photoqueue.phototoload.notifyAll();
}
//如果尚未启动,则启动线程
if(photoLoaderThread.getState()==Thread.State.NEW)
photoLoaderThread.start();
}
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);
康涅狄格州