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我正在制作一个Android应用程序，我试图在列表视图中加载和缓存图像。我从here得到了代码。这个Github项目的例子对我来说工作得很好，但是当我尝试在我的应用程序中使用相同的例子时，它的dosnt工作。这是我的ImageManager类。图像不延迟加载和缓存
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/floapp");
System.out
.println("coming here in mounted media and created folder floapp");
} 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.ic_launcher);
}
}
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) {
System.out.println("coming in getbitmap");
String filename = String.valueOf(url.hashCode());
File f = new File(cacheDir, filename);
System.out.println("cachedir=" + cacheDir.getPath());
System.out.println("filename=" + filename);
// Is the bitmap in our cache?
Bitmap bitmap = BitmapFactory.decodeFile(f.getPath());
System.out.println("bitmap after decoding the file thingy file path="
+ 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 {
// @Override
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.ic_launcher);
}
}
}
}
我得到FileNotFoundException，但文件正在我的SD卡上的文件夹中创建。谁能帮帮我吗？？
- 预先感谢
更新： 我想这跟url有关。我从here得到了一个提示。我的网址是这样的 “http://graph.facebook.com/1519317701/picture”
where throw'FileNotFoundException'，'cacheDir = new File（sdDir，“data/floapp”）;'here或where？ – idiottiger 2012-02-23 09:56:50
对不起，我的坏。早些时候应该提到它。错误在位图bitmap = BitmapFactory.decodeFile（f.getPath（））; – Antrromet 2012-02-23 09:59:09
打印语句工作得很好。 cachedir的输出是 cachedir =/mnt/sdcard/data/floapp – Antrromet 2012-02-23 10:01:33