我需要从净在列出的数据我有1图像和2文本。我分析所有数据并显示,但图像显示在列表中很慢。所以我想找做到这一点最好的办法。
i need to list out data from net in that i have 1 image and 2 text. i parse all data and display it but the image displaying very slow in list. so i m looking for best way to do this.
请帮我了。
在此先感谢
请复制下面的类。那类是从网络下载图像和存储于 存储卡或到应用程序的内存中。
Please copy the below class . That class is download the images from the web and stores into the memory card or into internal memory of application .
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Stack;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.widget.ImageView;
public class Imageloader
{
// 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 = null;
private Bitmap useThisBitmap = null;
@SuppressWarnings("unused")
private Context ctx = null;
public Imageloader(Context context)
{
// Make the background thead low priority. This way it will not affect
// the UI performance
ctx = 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(),"DownloadImages/AlbumArt/");
else
cacheDir = context.getCacheDir();
if (!cacheDir.exists())
cacheDir.mkdirs();
}
public void DisplayImage(String url, Activity activity, ImageView imageView)
{
if(!url.equals(""))
{
if (cache.containsKey(url))
{
imageView.setImageBitmap(cache.get(url));
}
else
{
queuePhoto(url, activity, imageView);
}
}
}
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();
}
public Bitmap getBitmap(String url)
{
try
{
// 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;
if(!url.equals("")){
InputStream is = new URL(url).openStream();
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
}
return bitmap;
}
catch (Exception ex)
{
ex.printStackTrace();
return null;
}
}
catch(Exception e)
{
e.printStackTrace();
return null;
}
}
/*decodes image and scales it to reduce memory consumption
* @param file path
* @throws FileNotFoundException
* @return bitmap
* */
private Bitmap decodeFile(File f){
Bitmap b = null;
try {
useThisBitmap = null;
//Decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
final int IMAGE_MAX_SIZE = 70;
BitmapFactory.decodeStream(new FileInputStream(f), null, o);
int scale = 2;
if (o.outHeight > IMAGE_MAX_SIZE || o.outWidth > IMAGE_MAX_SIZE) {
scale = 2 ^ (int) Math.ceil(Math.log(IMAGE_MAX_SIZE / (double) Math.max(o.outHeight, o.outWidth)) / Math.log(0.5));
}
//Decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
b = BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
useThisBitmap = b;
}
catch (FileNotFoundException e) {
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
System.gc();
}
return useThisBitmap;
}
// Task for the queue
private class PhotoToLoad
{
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i) {
url = u;
imageView = i;
}
}
private PhotosQueue photosQueue = new PhotosQueue();
// stores list of photos to download
private class PhotosQueue
{
private Stack<PhotoToLoad> photosToLoad = new Stack<PhotoToLoad>();
// removes all instances of this ImageView
private void Clean(ImageView image)
{
for (int j = 0; j < photosToLoad.size();)
{
if (photosToLoad.get(j).imageView == image)
photosToLoad.remove(j);
else
++j;
}
}
}
private 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);
if (((String) photoToLoad.imageView.getTag())
.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
}
}
}
private PhotosLoader photoLoaderThread = new PhotosLoader();
// Used to display bitmap in the UI thread
private class BitmapDisplayer implements Runnable
{
private Bitmap bitmap;
private ImageView imageView;
private BitmapDisplayer(Bitmap b, ImageView i)
{
bitmap = b;
imageView = i;
}
public void run()
{
if (bitmap != null)
imageView.setImageBitmap(bitmap);
}
}
public void stopThread()
{
photoLoaderThread.interrupt();
}
public void clearCache()
{
cache.clear();
File[] files = cacheDir.listFiles();
for (File f : files)
f.delete();
}
}
首先创建映像加载类的对象。
First create your image Loader class object.
Imageloader imageLoader = new Imageloader(getApplicationContext());
然后设置图片的网址进入的ImageView setTag
属性。
imgImageView.setTag(Your Image Url);
再打电话给你ImageLoader的类显示图像的功能。有需要的3个参数。
then call your ImageLoader class Display image function . There are 3 parameters required.
1)图片的网址
2)您当前的类名
3)的ImageView
3) ImageView
imageLoader.DisplayImage(Your Image Url,ClassName.this,imgImageView);
从web此functon下载中心图像和存储在存储器,并显示从存储器
this functon dowload images from the web and stored into the memory and show from the memory.