从Url下载图像时如何给出进度条

时间:2012-11-10 04:12:05

标签: android android-progressbar

我有一个来自该课程的ImageDownloader课程我通过从ArrayList传递一些网址来点击按钮下载图片。那么如何在按下下载动作按钮后给出进度条,以及如何知道当它完成下载时我们可以关闭对话框。以下是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();
    }

}

2 个答案:

答案 0 :(得分:4)

 call this class for file Download :=
 new DownloadFileFromURL().execute(file_url);


 /**
 * Background Async Task to download file
 * */
class DownloadFileFromURL extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread
     * Show Progress Bar Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        showDialog(progress_bar_type);
    }

    /**
     * Downloading file in background thread
     * */
    @Override
    protected String doInBackground(String... f_url) {
        int count;
        try {
            URL url = new URL(f_url[0]);
            URLConnection conection = url.openConnection();
            conection.connect();
            // getting file length
            int lenghtOfFile = conection.getContentLength();

            // input stream to read file - with 8k buffer
            InputStream input = new BufferedInputStream(url.openStream(), 8192);

            // Output stream to write file
            OutputStream output = new FileOutputStream("/sdcard/downloadedfile.jpg");

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                // After this onProgressUpdate will be called
                publishProgress(""+(int)((total*100)/lenghtOfFile));

                // writing data to file
                output.write(data, 0, count);
            }

            // flushing output
            output.flush();

            // closing streams
            output.close();
            input.close();

        } catch (Exception e) {
            Log.e("Error: ", e.getMessage());
        }

        return null;
    }

    /**
     * Updating progress bar
     * */
    protected void onProgressUpdate(String... progress) {
        // setting progress percentage
        pDialog.setProgress(Integer.parseInt(progress[0]));
   }

    /**
     * After completing background task
     * Dismiss the progress dialog
     * **/
    @Override
    protected void onPostExecute(String file_url) {
        // dismiss the dialog after the file was downloaded
        dismissDialog(progress_bar_type);

        // Displaying downloaded image into image view
        // Reading image path from sdcard
        String imagePath = Environment.getExternalStorageDirectory().toString() + "/downloadedfile.jpg";
        // setting downloaded into image view
        my_image.setImageDrawable(Drawable.createFromPath(imagePath));
    }

}

答案 1 :(得分:0)

你真的应该使用AsynchTask,文档示例正是你想要做的事情,并且找到here