有人请检查我的代码。我的进度对话框刚出现，在我看到它之前就这么快就解散了。它假设在下载过程中显示进度对话框。但是我的进度对话框在我的图像加载之前就消失了。
public class SingleImageViewActivity extends SherlockActivity {
// XML node keys
static final String KEY_TITLE = "title";
static final String KEY_ARTIST = "artist";
static final String KEY_THUMB_URL = "thumb_url";
static final String KEY_BIG_URL = "big_url";
private ProgressDialog pDialog;
String title;
String artist;
//String image_url;
String big_image_url;
ImageView view;
Intent intent;
Context context;
ShareActionProvider mShareActionProvider;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.single_view_item);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
//checkInternetConnection();
new loadSingleView().execute();
view = (ImageView) findViewById(R.id.single_image);
}
public class loadSingleView extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(SingleImageViewActivity.this);
pDialog.setTitle("Connect to Server");
pDialog.setMessage("This process can take a few seconds to a few minutes, depending on your Internet Connection Speed.");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected String doInBackground(String... args) {
// updating UI from Background Thread
Intent in = getIntent();
//image_url = in.getStringExtra(KEY_THUMB_URL);
big_image_url = in.getStringExtra(KEY_BIG_URL);
title = in.getStringExtra(KEY_TITLE);
artist = in.getStringExtra(KEY_ARTIST);
SingleViewImageLoader imgLoader = new SingleViewImageLoader(getApplicationContext());
imgLoader.DisplayImage(big_image_url, view);
return null;
}
@Override
protected void onPostExecute(String args) {
// dismiss the dialog after getting all products
TextView lblName = (TextView) findViewById(R.id.name_title);
TextView lblCost = (TextView) findViewById(R.id.name_artist);
lblName.setText(title);
lblCost.setText(artist);
ActionBar ab = getSupportActionBar();
ab.setTitle(title);
ab.setSubtitle(artist);
pDialog.dismiss();
}
}
SingleViewImageLoader.class
public class SingleViewImageLoader {
MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;
public SingleViewImageLoader(Context context){
fileCache=new FileCache(context);
executorService=Executors.newFixedThreadPool(5);
}
final int stub_id = R.drawable.no_image;
public void DisplayImage(String url, ImageView imageView)
{
imageViews.put(imageView, url);
Bitmap bitmap=memoryCache.get(url);
if(bitmap!=null)
imageView.setImageBitmap(bitmap);
else
{
queuePhoto(url, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, ImageView imageView)
{
PhotoToLoad p=new PhotoToLoad(url, imageView);
executorService.submit(new PhotosLoader(p));
}
private 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(30000);
conn.setReadTimeout(30000);
conn.setInstanceFollowRedirects(true);
InputStream is=conn.getInputStream();
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);
//Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE=500;
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 PhotoToLoad(String u, ImageView i){
url=u;
imageView=i;
}
}
class PhotosLoader implements Runnable {
PhotoToLoad photoToLoad;
PhotosLoader(PhotoToLoad photoToLoad){
this.photoToLoad=photoToLoad;
}
@Override
public void run() {
if(imageViewReused(photoToLoad))
return;
Bitmap bmp=getBitmap(photoToLoad.url);
memoryCache.put(photoToLoad.url, bmp);
if(imageViewReused(photoToLoad))
return;
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
Activity a=(Activity)photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
boolean imageViewReused(PhotoToLoad photoToLoad){
String tag=imageViews.get(photoToLoad.imageView);
if(tag==null || !tag.equals(photoToLoad.url))
return true;
return false;
}
//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
PhotoToLoad photoToLoad;
public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
public void run()
{
if(imageViewReused(photoToLoad))
return;
if(bitmap!=null)
photoToLoad.imageView.setImageBitmap(bitmap);
else
photoToLoad.imageView.setImageResource(stub_id);
}
}
public void clearCache() {
memoryCache.clear();
fileCache.clear();
}
}
答案 0 :(得分：3)
由于Image Loader类也使用线程来显示图像，因此它在后台运行并调用onPostExecute（）方法并关闭进度对话框。