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| package com.example;
import java.io.File;
import java.io.FileOutputStream;
import java.lang.ref.SoftReference;
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 ImageManager {
private HashMap<String, SoftReference<Bitmap>> imageMap = new HashMap<String, SoftReference<Bitmap>>();
private File cacheDir;
private ImageQueue imageQueue = new ImageQueue();
private Thread imageLoaderThread = new Thread(new ImageQueueManager());
public ImageManager(Context context) {
// Make background thread low priority, to avoid affecting UI performance
imageLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
// Find the dir to save cached images
String sdState = android.os.Environment.getExternalStorageState();
if (sdState.equals(android.os.Environment.MEDIA_MOUNTED)) {
File sdDir = android.os.Environment.getExternalStorageDirectory();
cacheDir = new File(sdDir,"data/codehenge");
}
else
cacheDir = context.getCacheDir();
if(!cacheDir.exists())
cacheDir.mkdirs();
}
public void displayImage(String url, Activity activity, ImageView imageView) {
if(imageMap.containsKey(url))
imageView.setImageBitmap(imageMap.get(url).get());
else {
queueImage(url, activity, imageView);
imageView.setImageResource(R.drawable.icon);
}
}
private void queueImage(String url, Activity activity, ImageView imageView) {
// This ImageView might have been used for other images, so we clear
// the queue of old tasks before starting.
imageQueue.Clean(imageView);
ImageRef p=new ImageRef(url, imageView);
synchronized(imageQueue.imageRefs) {
imageQueue.imageRefs.push(p);
imageQueue.imageRefs.notifyAll();
}
// Start thread if it's not started yet
if(imageLoaderThread.getState() == Thread.State.NEW)
imageLoaderThread.start();
}
private Bitmap getBitmap(String url) {
String filename = String.valueOf(url.hashCode());
File f = new File(cacheDir, filename);
// Is the bitmap in our cache?
Bitmap bitmap = BitmapFactory.decodeFile(f.getPath());
if(bitmap != null) return bitmap;
// Nope, have to download it
try {
bitmap = BitmapFactory.decodeStream(new URL(url).openConnection().getInputStream());
// save bitmap to cache for later
writeFile(bitmap, f);
return bitmap;
} catch (Exception ex) {
ex.printStackTrace();
return null;
}
}
private void writeFile(Bitmap bmp, File f) {
FileOutputStream out = null;
try {
out = new FileOutputStream(f);
bmp.compress(Bitmap.CompressFormat.PNG, 80, out);
} catch (Exception e) {
e.printStackTrace();
}
finally {
try { if (out != null ) out.close(); }
catch(Exception ex) {}
}
}
/** Classes **/
private class ImageRef {
public String url;
public ImageView imageView;
public ImageRef(String u, ImageView i) {
url=u;
imageView=i;
}
}
//stores list of images to download
private class ImageQueue {
private Stack<ImageRef> imageRefs =
new Stack<ImageRef>();
//removes all instances of this ImageView
public void Clean(ImageView view) {
for(int i = 0 ;i < imageRefs.size();) {
if(imageRefs.get(i).imageView == view)
imageRefs.remove(i);
else ++i;
}
}
}
private class ImageQueueManager implements Runnable {
public void run() {
try {
while(true) {
// Thread waits until there are images in the
// queue to be retrieved
if(imageQueue.imageRefs.size() == 0) {
synchronized(imageQueue.imageRefs) {
imageQueue.imageRefs.wait();
}
}
// When we have images to be loaded
if(imageQueue.imageRefs.size() != 0) {
ImageRef imageToLoad;
synchronized(imageQueue.imageRefs) {
imageToLoad = imageQueue.imageRefs.pop();
}
Bitmap bmp = getBitmap(imageToLoad.url);
imageMap.put(imageToLoad.url, new SoftReference<Bitmap>(bmp));
Object tag = imageToLoad.imageView.getTag();
// Make sure we have the right view - thread safety defender
if(tag != null && ((String)tag).equals(imageToLoad.url)) {
BitmapDisplayer bmpDisplayer =
new BitmapDisplayer(bmp, imageToLoad.imageView);
Activity a =
(Activity)imageToLoad.imageView.getContext();
a.runOnUiThread(bmpDisplayer);
}
}
if(Thread.interrupted())
break;
}
} catch (InterruptedException e) {}
}
}
//Used to display bitmap in the UI thread
private 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(R.drawable.icon);
}
}
} |
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