我有这个代码从网上显示图像并将其保存为缓存，但我总是得到一个NullPointer。
ImageView projectImage = (ImageView)findViewById(R.id.project_image);
setViewImage(projectImage, project.bigImageUrl);
public void setViewImage(ImageView v, String value) {
v.setTag(value);
System.out.println(value);
System.out.println(activity);
System.out.println(v);
loader.displayImage(value, activity, v);
}
这是stakcktrace：
05-20 11:28:35.415: INFO/System.out(645): http://cdn.spendino.de/web/img/projects/small/1264073994.jpg
05-20 11:28:35.425: INFO/System.out(645): spendino.de.ProjectDetail@43c0ee08
05-20 11:28:35.435: INFO/System.out(645): android.widget.ImageView@43be1550
05-20 11:28:35.535: ERROR/AndroidRuntime(645): Caused by: java.lang.NullPointerException
05-20 11:28:35.535: ERROR/AndroidRuntime(645): at spendino.de.ProjectDetail.setViewImage(ProjectDetail.java:81)
05-20 11:28:35.535: ERROR/AndroidRuntime(645): at spendino.de.ProjectDetail.onCreate(ProjectDetail.java:48)
这是ImageLoader类：
public class ImageLoaderCache {
Context context;
//the simplest in-memory cache implementation. This should be replaced with something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
/** The cache. */
private HashMap<String, Bitmap> cache=new HashMap<String, Bitmap>();
/** The cache dir. */
private File cacheDir;
/**
* Instantiates a new image loader.
*
* @param context the context
*/
public ImageLoaderCache(Context context){
//Make the background thead low priority. This way it will not affect the UI performance
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(),"spendino.de");
else
cacheDir=context.getCacheDir();
if(!cacheDir.exists())
cacheDir.mkdirs();
}
//This is used for a stub when the user can not see the actual image..
//this images will be seen
final int stub_id =R.drawable.list_icon;
/**
* Display image.
*
* @param url the url
* @param activity the activity
* @param imageView the image view
*/
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);
}
}
/**
* Queue photo.
*
* @param url the url
* @param activity the activity
* @param imageView the image view
*/
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();
}
/**
* Gets the bitmap.
*
* @param url the url
* @return the bitmap
*/
private Bitmap getBitmap(String url)
{
String filename = String.valueOf(url.substring(url.lastIndexOf("/") + 1));
File f = new File(cacheDir, filename);
// from web
try
{
if(!f.exists())
{
Bitmap bitmap = null;
InputStream is = new URL(url).openStream();
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
}
else
{
Bitmap bitmap = decodeFile(f);
return bitmap;
}
}
catch (Exception ex)
{
ex.printStackTrace();
BitmapDrawable mDrawable = (BitmapDrawable) context.getResources().getDrawable(R.drawable.list_icon);
return mDrawable.getBitmap();
}
}
//decodes image and scales it to reduce memory consumption
/**
* Decode file.
*
* @param f the f
* @return the bitmap
*/
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++;
}
//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
/**
* The Class PhotoToLoad.
*/
private class PhotoToLoad
{
/** The url. */
public String url;
/** The image view. */
public ImageView imageView;
/**
* Instantiates a new photo to load.
*
* @param u the u
* @param i the i
*/
public PhotoToLoad(String u, ImageView i){
url=u;
imageView=i;
}
}
/** The photos queue. */
PhotosQueue photosQueue=new PhotosQueue();
/**
* Stop thread.
*/
public void stopThread()
{
photoLoaderThread.interrupt();
}
//stores list of photos to download
/**
* The Class PhotosQueue.
*/
class PhotosQueue
{
/** The photos to load. */
private Stack<PhotoToLoad> photosToLoad=new Stack<PhotoToLoad>();
//removes all instances of this ImageView
/**
* Clean.
*
* @param image the image
*/
public void Clean(ImageView image)
{
for(int j=0 ;j<photosToLoad.size();){
if(photosToLoad.get(j).imageView==image)
photosToLoad.remove(j);
else
++j;
}
}
}
/**
* The Class PhotosLoader.
*/
class PhotosLoader extends Thread {
/* (non-Javadoc)
* @see java.lang.Thread#run()
*/
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
}
}
}
/** The photo loader thread. */
PhotosLoader photoLoaderThread=new PhotosLoader();
//Used to display bitmap in the UI thread
/**
* The Class BitmapDisplayer.
*/
class BitmapDisplayer implements Runnable
{
/** The bitmap. */
Bitmap bitmap;
/** The image view. */
ImageView imageView;
/**
* Instantiates a new bitmap displayer.
*
* @param b the b
* @param i the i
*/
public BitmapDisplayer(Bitmap b, ImageView i){bitmap=b;imageView=i;}
/* (non-Javadoc)
* @see java.lang.Runnable#run()
*/
public void run()
{
if(bitmap!=null)
imageView.setImageBitmap(bitmap);
else
imageView.setImageResource(stub_id);
}
}
/**
* Clear cache.
*/
public void clearCache() {
//clear memory cache
cache.clear();
//clear SD cache
File[] files=cacheDir.listFiles();
for(File f:files)
f.delete();
}
public static void copyStream(InputStream is, OutputStream os) {
final int buffer_size=1024;
try
{
byte[] bytes=new byte[buffer_size];
for(;;)
{
int count=is.read(bytes, 0, buffer_size);
if(count==-1)
break;
os.write(bytes, 0, count);
}
}
catch(Exception ex){}
}
}
有人可以帮我解决问题吗？提前致谢
答案 0 :(得分：0)
private static InputStream fetch(String urlString)
throws MalformedURLException, IOException {
conn = (HttpURLConnection)(new URL(urlString)).openConnection();
conn.setDoInput(true);
conn.connect();
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpGet request = new HttpGet(urlString);
HttpResponse response = httpClient.execute(request);
return conn.getInputStream();
}
Resources res;
// ***********New Function For Fatching
public static Drawable LoadImage(String URL, BitmapFactory.Options options) {
Drawable drawable = null; Bitmap bm = null;
try {
if (fetch(URL) != null) {
try {
InputStream obj = (InputStream)fetch(URL);
bm = BitmapFactory.decodeStream(obj,null,options);
obj.close();
conn.disconnect();
} catch(OutOfMemoryError e){}
catch(IndexOutOfBoundsException e){}
drawable = new BitmapDrawable(bm);
return drawable;
} else {
bitmap = BitmapFactory.decodeResource(
DefaultDisplay.mContext.getResources(),
R.drawable.profileplaceholder);
drawable = new BitmapDrawable(bitmap);
return drawable;
}
} catch (Exception e) {
Log.e("GUIMethodClasas", "fetchDrawable failed", e);
return null;
}
}
我正在使用此LoadImage函数来获取图像格式url它工作正常。只需根据位图质量传递url和bitmapoption值，如1,2,3,4,5。 我希望你得到答案。