我有一个ImageDownloader来自那个班级的班级，我通过从ArrayList. 那么如何在按下下载操作按钮后给出进度条以及如何知道它何时完成下载以便我们可以关闭对话框。下面是ImageDownloader类。
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.HttpURLConnection;
import java.net.URL;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Stack;
import java.util.WeakHashMap;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.util.Log;
import android.widget.ImageView;
public class ImageLoader {
MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
static Bitmap bitmap;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
String detail;
public ImageLoader(Context context){
//Make the background thead low priority. This way it will not affect the UI performance
photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
fileCache=new FileCache(context);
}
// final int stub_id=R.drawable.stub;
public void DisplayImage(String url,ImageView imageView,String detail)
{
imageViews.put(imageView, url);
this.detail=detail;
Bitmap bitmap=memoryCache.get(url);
if(bitmap!=null){
int reqHgt=(bitmap.getHeight()*Home.d.getWidth())/bitmap.getWidth();
bitmap=Bitmap.createScaledBitmap(bitmap,Home.d.getWidth(),reqHgt,true);
imageView.setImageBitmap(bitmap);
}
else
{
queuePhoto(url, imageView);
}
}
private void queuePhoto(String url, 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();
}
Bitmap getBitmap(String url)
{
File f=fileCache.getFile(url);
//from SD cache
Bitmap b = decodeFile(f);
if(b!=null)
return b;
//from web
try {
Bitmap bitmap=null;
URL imageUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
conn.setConnectTimeout(15000);
conn.setReadTimeout(15000);
InputStream is=conn.getInputStream();
Log.w("INput",is.toString());
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex){
ex.printStackTrace();
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);
Log.w("called2","called2");
//Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE=550;
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) {
e.printStackTrace();
}
return null;
}
//Task for the queue
private class PhotoToLoad
{
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i){
url=u;
imageView=i;
}
}
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);
if(detail!=null){
int reqHgt=(bmp.getHeight()*Home.d.getWidth())/bmp.getWidth();
bmp=Bitmap.createScaledBitmap(bmp,Home.d.getWidth(),reqHgt,true);
}
memoryCache.put(photoToLoad.url, bmp);
String tag=imageViews.get(photoToLoad.imageView);
if(tag!=null && tag.equals(photoToLoad.url)){
Log.e("koti-----","-----koti");
int reqHgt=(bmp.getHeight()*Home.d.getWidth())/bmp.getWidth();
bmp=Bitmap.createScaledBitmap(bmp,Home.d.getWidth(),reqHgt,true);
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
}
}
}
PhotosLoader photoLoaderThread=new PhotosLoader();
//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
ImageView imageView;
public BitmapDisplayer(Bitmap b, ImageView i){bitmap=b;imageView=i;}
public void run()
{
if(bitmap!=null)
// reqHgt=(bmp.getHeight()*Welcome.d.getWidth())/bmp.getWidth();
Log.w("called4","called4");
imageView.setBackgroundDrawable(new BitmapDrawable(bitmap));
}
}
public Bitmap getLatestBitmap()
{
return bitmap;
}
public void clearCache() {
memoryCache.clear();
fileCache.clear();
}
}