我是Android上的新手我希望在背景中设置图像从Url获取..我正在使用ImageLoader类 请帮帮我在背景中设置图像视图..
这是我的图像加载程序类
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;
static ArrayList<String> img_path = new ArrayList<String>();
static String sd_card_folder_name = "ImageLoader";
static int width;
public ImageLoader(Context context, Activity acc) {
// Make the background thead low priority. This way it will not affect
// the UI performance
photoLoaderThread.setPriority(Thread.NORM_PRIORITY - 1);
DisplayMetrics displaymetrics = new DisplayMetrics();
acc.getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
width = displaymetrics.widthPixels;
Log.d("width", "width = " + width);
cache.clear();
img_path = new ArrayList<String>();
// 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(), sd_card_folder_name);
else
cacheDir = context.getCacheDir();
if (!cacheDir.exists())
cacheDir.mkdirs();
}
final int stub_id = R.drawable.loader;
public void DisplayImage(String url, Activity activity, ImageView imageView) {
try {
String filename = String.valueOf(url.hashCode());
File[] file_array = cacheDir.listFiles();
for (int i = 0; i < file_array.length; i++) {
img_path.add(file_array[i].getName());
}
if (img_path.contains(filename)) {
imageView.setImageBitmap(BitmapFactory
.decodeFile("/mnt/sdcard/" + sd_card_folder_name + "/"
+ filename));
} else {
if (cache.containsKey(url)) {
imageView.setImageBitmap(cache.get(url));
} else {
queuePhoto(url, activity, imageView, filename);
imageView.setImageResource(stub_id);
}
}
} catch (Exception e) {
// TODO: handle exception
}
}
private void queuePhoto(String url, Activity activity, ImageView imageView, String _name) {
// 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, _name);
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.
if (url != null && !(url.equals(""))) {
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 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;
}
}
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=300;
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 String _name;
public PhotoToLoad(String u, ImageView i, String n) {
url = u;
imageView = i;
_name = n;
}
}
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();
String FileName = photoToLoad._name;
if (FileName != null
&& ((String) FileName).equals(photoToLoad._name)) {
BitmapDisplayer bd = new BitmapDisplayer(bmp,
photoToLoad.imageView, FileName);
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;
String file_name;
public BitmapDisplayer(Bitmap b, ImageView i, String _name) {
bitmap = b;
imageView = i;
file_name = _name;
}
public void run() {
if (bitmap != null) {
load_full_image(imageView, file_name, bitmap);
} else
imageView.setImageResource(stub_id);
}
}
private Runnable mMyRunnable = new Runnable() {
@Override
public void run() {
}
};
public void load_full_image(ImageView img, String _name, Bitmap btmp) {
img_path = new ArrayList<String>();
File[] file_array = cacheDir.listFiles();
for (int i = 0; i < file_array.length; i++) {
img_path.add(file_array[i].getName());
}
if (img_path.contains(_name)) {
img.setImageBitmap(BitmapFactory
.decodeFile("/mnt/sdcard/" + sd_card_folder_name + "/"
+ _name));
} else {
img.setImageBitmap(btmp);
}
}
public void clearCache() {
// clear memory cache
cache.clear();
// clear SD cache
File[] files = cacheDir.listFiles();
for (File f : files)
f.delete();
}
这是我在imagview中获取图像的活动
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.userprofile);
Button addfrnd=(Button)findViewById(R.id.addfrnd);
ImageView image = (ImageView) findViewById(R.id.imageView1);
UserModel user = (UserModel) getIntent().getSerializableExtra("User");
UserByIdModel tempuser = (UserByIdModel) getIntent().getSerializableExtra("UserById");
String UserId=String.valueOf(tempuser.getUser_Id());
String image_url=tempuser.getUser_Image();
int loader = R.drawable.loader;
ImageLoader imgLoader = new ImageLoader(getApplicationContext(),
UserByIdProfile.this);
image.setTag(image_url);
// whenever you want to load an image from url
// call DisplayImage function
// url - image url to load
// loader - loader image, will be displayed before getting image
// image - ImageView
imgLoader.DisplayImage(image_url, UserByIdProfile.this, image);
答案 0 :(得分：1)
您必须更改 imageLoader 类的 load_full_image 方法，如下所示
public class ImageLoader {
...
Context mContext;
...
public ImageLoader(Context context, Activity acc) {
...
mContext = context
....
}
public void load_full_image(ImageView img, String _name, Bitmap btmp) {
img_path = new ArrayList<String>();
File[] file_array = cacheDir.listFiles();
for (int i = 0; i < file_array.length; i++) {
img_path.add(file_array[i].getName());
}
if (img_path.contains(_name)) {
Drawable d = new BitmapDrawable(mContext.getResources(),BitmapFactory
.decodeFile("/mnt/sdcard/" + sd_card_folder_name + "/"
+ _name));
img.setBackground(d);
} else {
Drawable d = new BitmapDrawable(mContext.getResources(),btmp);
img.setBackground(d);
}
}
}
尝试此代码可能会起作用
答案 1 :(得分：0)
您已创建ImageLoader的实例但尚未初始化ImageLoader。为此，在imageLoader = ImageLoader.getInstance（）之后在构造函数中添加这行代码; ：
imageLoader.init（ImageLoaderConfiguration.createDefault（CTX））;
您尚未为imageLoader声明任何选项。修改DisplayImageOptions代码，如下所示：
DisplayImageOptions options = new DisplayImageOptions.Builder（）.showImageOnLoading（R.drawable.image_loading）.showImageForEmptyUri（R.drawable.no_image）.showImageOnFail（R.drawable.image_failed）.cacheInMemory（true）.cacheOnDisc（true）。 bitmapConfig（Bitmap.Config.RGB_565）.build（）;
答案 2 :(得分：-1)
[Use this project aims to provide a reusable instrument for asynchronous image loading, caching and displaying.][1]
Features
1)Multithread image loading (async or sync)
2)Wide customization of ImageLoader's configuration (thread executors, downloader, decoder, 3)memory and disk cache, display image options, etc.)
4)Many customization options for every display image call (stub images, caching switch, decoding options, Bitmap processing and displaying, etc.)
5)Image caching in memory and/or on disk (device's file system or SD card)
6)Listening loading process (including downloading progress)
*****Android 2.0+ support
[1]: https://github.com/nostra13/Android-Universal-Image-Loader