问题
I'm new to Android and Java. I have been working on my task i.e, Image Downloader. Where I have to download images with progress bar and display them in grid. I have created two classes 1. URLImageAdapter 2. CacheActivity. Everything works fine but download begins before I click on download button and when I click on download button the progress bar appears and progress till hundred vanishes but still downloading is on. I want to synchronize downloading images and progress bar.
Code Below. Any Help
public class URLImageAdapter extends BaseAdapter {
private class Image {
String url;
Bitmap thumb;
}
private Image[] images;
private Context myContext;
private LoadThumbsTask thumbnailGen;
private Object previousList;
public URLImageAdapter(Context c) {
myContext = c;
thumbnailGen = new LoadThumbsTask();
if (previousList != null) {
images = (Image[]) previousList;
thumbnailGen.execute(images);
return;
}
images = new Image[imageURLs.length];
for (int i = 0, j = imageURLs.length; i < j; i++) {
images[i] = new Image();
images[i].url = imageURLs[i];
}
thumbnailGen.execute(images);
}
public int getCount() {
return images.length;
}
public Object getItem(int position) {
return images[position].url;
}
public long getItemId(int position) {
return position;
}
public Object getData() {
if (thumbnailGen != null
&& thumbnailGen.getStatus() != AsyncTask.Status.FINISHED) {
thumbnailGen.cancel(true);
}
return images;
}
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imgView;
Image cached = images[position];
if (convertView == null) {
imgView = new ImageView(myContext);
imgView.setLayoutParams(new GridView.LayoutParams(100, 100));
} else {
imgView = (ImageView) convertView;
}
if (cached.thumb == null) {
imgView.setImageResource(R.drawable.ic_action_search);
imgView.setScaleType(ScaleType.CENTER);
} else {
imgView.setScaleType(ScaleType.FIT_CENTER);
imgView.setImageBitmap(cached.thumb);
}
return imgView;
}
private void cacheUpdated() {
this.notifyDataSetChanged();
}
private Bitmap loadThumb(String url) {
Bitmap thumb = null;
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inSampleSize = 4;
try {
URL u = new URL(url);
URLConnection c = u.openConnection();
c.connect();
BufferedInputStream stream = new BufferedInputStream(
c.getInputStream());
thumb = BitmapFactory.decodeStream(stream, null, opts);
stream.close();
} catch (MalformedURLException e) {
Log.e("ERROR", "malformed url: " + url);
} catch (IOException e) {
Log.e("ERROR", "An error has occurred downloading the image: "
+ url);
}
return thumb;
}
private class LoadThumbsTask extends AsyncTask<Image, Void, Void> {
@Override
protected Void doInBackground(Image... cache) {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inSampleSize = 4;
for (Image i : cache) {
if (isCancelled())
return null;
if (i.thumb != null)
continue;
SystemClock.sleep(500);
i.thumb = loadThumb(i.url);
publishProgress();
}
return null;
}
@Override
protected void onProgressUpdate(Void... param) {
cacheUpdated();
}
}
private String[] imageURLs = {
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_2851.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_2944.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_2989.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3005.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3012.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3034.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3047.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3092.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3110.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3113.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3128.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3160.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3226.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3228.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3251.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3268.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3275.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3346.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3365.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3374.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3385.jpg",
"http://cdn.cs76.net/2011/spring/lectures/6/imgs/img_3392.jpg", };
}
CacheActivity
public class CacheActivity extends Activity {
Button btnStartProgress;
ProgressDialog progressBar;
private int progressBarStatus = 0;
private Handler progressBarHandler = new Handler();
private long fileSize = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cache);
GridView gridview = (GridView) findViewById(R.id.grid_view);
gridview.setAdapter(new URLImageAdapter(this));
addListenerOnButton();
}
public void addListenerOnButton() {
btnStartProgress = (Button) findViewById(R.id.btnStartProgress);
btnStartProgress.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
progressBar = new ProgressDialog(v.getContext());
progressBar.setCancelable(true);
progressBar.setMessage("File downloading ...");
progressBar.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressBar.setProgress(0);
progressBar.setMax(100);
progressBar.show();
progressBarStatus = 0;
fileSize = 0;
new Thread(new Runnable() {
public void run() {
while (progressBarStatus < 100) {
progressBarStatus = doInBackground();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
progressBarHandler.post(new Runnable() {
public void run() {
progressBar.setProgress(progressBarStatus);
}
});
}
if (progressBarStatus >= 100) {
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
progressBar.dismiss();
}
}
}).start();
}
});
}
public int doInBackground() {
while (fileSize <= 1000000) {
fileSize++;
if (fileSize == 100000) {
return 10;
} else if (fileSize == 200000) {
return 20;
} else if (fileSize == 300000) {
return 30;
}else if (fileSize == 400000) {
return 40;
}else if (fileSize == 500000) {
return 50;
}else if (fileSize == 600000) {
return 60;
}else if (fileSize == 700000) {
return 70;
}else if (fileSize == 800000) {
return 80;
}else if (fileSize == 900000) {
return 90;
}
}
return 100;
}
}
回答1:
download image in using
public class LoginProgress extends AsyncTask<Object, Object, Object> {
private ProgressDialog dialog;
@Override
protected void onPreExecute() {
this.dialog = ProgressDialog.show(applicationContext, "Please wait down",
"Loading .....", true);
}
@Override
protected Object doInBackground(Object... params) {
// TODO Auto-generated method stub
return null;
}
@Override
protected void onPostExecute(Void unused) {
//Intent for next activity
this.dialog.dismiss();
}
}
create object for these class in button click
LoginProgress task = new LoginProgress();
task.execute();
call ur doinbackground method in these doinbackground methode
otherwise do following two
increment time of Thread.sleep(1000); change to Thread.sleep(4000); Thread.sleep(200); change to Thread.sleep(450);
you set gridview.setAdapter(new URLImageAdapter(CacheActivity.this)); in oncreate , remove this adapter in oncreate and write it in end of on click method...
回答2:
The problem is that you don't pass any values to publishProgress() of your LoadThumbsTask
Pass some value to this method (e.g. number of already downloaded thumbs), and then in onProgressUpdate() update your ProgressDialog based on this value.
回答3:
public int doInBackground() {
while (fileSize <= 1000000) {
fileSize++;
if (fileSize == 100000) {
return 10;
} else if (fileSize == 200000) {
return 20;
} else if (fileSize == 300000) {
return 30;
}else if (fileSize == 400000) {
return 40;
}else if (fileSize == 500000) {
return 50;
}else if (fileSize == 600000) {
return 60;
}else if (fileSize == 700000) {
return 70;
}else if (fileSize == 800000) {
return 80;
}else if (fileSize == 900000) {
return 90;
}
}
return 100;
}
it's not tied to the actual file size. it should be something like
return (currentFilesize/totalFilesize)*100
and not just raw values like these.
回答4:
As per my experience, Progressbar has refresh issue when It's inside listview or gridview, If you only want to indicate progress I suggest to develop your own control which looks like progressbar with RelativeLayout.
Take relativelayout and add imageview in that. and increase width of imageview to illustrate like progress.
I can post code if you wish, I have develop one such progress for myself
UPDATE : I found good post for that same, Following post indicate same technique which I describe.
http://blog.mediarain.com/2011/04/android-custom-progressbar-with-rounded-corners/
Demo Downloadable : http://blog.mediarain.com/wp-content/uploads/2011/04/RoundedProgressSample.zip
I hope above content will help you Thank You.
来源：https://stackoverflow.com/questions/13415804/android-progress-not-working-accordingly