How to set image from Url using AsyncTask?

Question

I\'m a newbie programmer an I\'m making an android program that displays an image on ImageView from a given url. My problem is how do you use this on the AsyncTask?

Thes

Answer 1

based on the answer from comeGetSome i created my own implementation which works with normal ImageView class instead of creating a new class UrlImageView, also new options are provided like - what to do when the loading completes or cancels

Now load image as you want, like this from any of the three loadImage methods

       UrlImageLoader urlImageLoader=new UrlImageLoader();
       ImageView imageView=new ImageView(context);
       //load and set the image to ImageView
       urlImageLoader.loadImage(imageView, "http://www......com/.....jpg");
       //for loading a image only - load image and do any thing with the bitmap
       urlImageLoader.loadImage("http://www......com/.....jpg", new UrlImageLoader.OnLoadingCompleteListener() {

            @Override
            public void onComplete(ImageView imageView, Bitmap bmp) {
                // do anything with the Bitmap
                // here imageView will be null
            }
            @Override
            public void onCancel(ImageView imageView) {

            }
        });
       urlImageLoader.loadImage(imageView, "http://www......com/.....jpg", new UrlImageLoader.OnLoadingCompleteListener() {

            @Override
            public void onComplete(ImageView imageView, Bitmap bmp) {
                // do anything with the Bitmap
                // here imageView is not null
                imageView.setImageBitmap(bmp);
            }
            @Override
            public void onCancel(ImageView imageView) {

            }
        });

create this class for loading UrlImageLoader

/*special thanks to stackoverflow.com user comeGetSome for UrlImageLoadingTask code
 * question - http://stackoverflow.com/questions/14332296/how-to-set-image-from-url-using-asynctask/15797963
 * comeGetSome - http://stackoverflow.com/users/1005652/comegetsome
 */
package com.GameG.SealTheBox;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.ImageView;

public class UrlImageLoader {
    public static interface OnLoadingCompleteListener {
        public void onComplete(ImageView imageView, Bitmap bmp);
        public void onCancel(ImageView imageView);
    }
    ArrayList<UrlImageLoadingTask> loadingList=new ArrayList<UrlImageLoadingTask>();
    /**
     * Loads a image from url and calls onComplete() when finished<br>
     * @Note you should manually set the loaded image to ImageView in the onComplete()
     * @param imageView
     * @param url
     * @param onComplete
     */
    public void loadImage(ImageView imageView, String url, OnLoadingCompleteListener onComplete){
        try {
            URL url2=new URL(url);
            if(imageView!=null){
                for(int i=0;i<loadingList.size();i++){
                    UrlImageLoadingTask tmptask=loadingList.get(i);
                    if(tmptask.updateView!=null && tmptask.updateView.equals(imageView)){
                        tmptask.cancel(true);
                        break;
                    }
                }
            }
            UrlImageLoadingTask loadtask=new UrlImageLoadingTask(imageView,onComplete,url);
            loadtask.execute(url2);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
    }

    /**
     * Loads a image from url and calls onComplete() when finished
     * @param url
     * @param onComplete
     */
    public void loadImage(String url, OnLoadingCompleteListener onComplete){
        loadImage(null,url,onComplete);
    }
    /**
     * Loads a image from url and sets the loaded image to ImageView
     * @param imageView
     * @param url
     */
    public void loadImage(ImageView imageView, String url){
        loadImage(imageView,url,null);
    }
    /**
     * Cancel loading of a ImageView
     */
    public void cancel(ImageView imageView){
        for(int i=0;i<loadingList.size();i++){
            UrlImageLoadingTask tmptask=loadingList.get(i);
            if(tmptask.updateView.equals(imageView)){
                loadingList.remove(i);
                tmptask.cancel(true);
                break;
            }
        }
    }
    /**
     * Cancel loading of a Url
     */
    public void cancel(String url){
        for(int i=0;i<loadingList.size();i++){
            UrlImageLoadingTask tmptask=loadingList.get(i);
            if(tmptask.url.equals(url)){
                loadingList.remove(i);
                tmptask.cancel(true);
                break;
            }
        }
    }
    /**
     * Cancel all loading tasks 
     */
    public void cancelAll(){
        while(loadingList.size()>0){
            UrlImageLoadingTask tmptask=loadingList.get(0);
            loadingList.remove(tmptask);
            tmptask.cancel(true);
        }
    }

    private class UrlImageLoadingTask extends AsyncTask<URL, Void, Bitmap> {
        public ImageView updateView=null;
        public String url;
        private boolean         isCancelled = false;
        private InputStream     urlInputStream;
        private OnLoadingCompleteListener onComplete=null;

        private UrlImageLoadingTask(ImageView updateView, OnLoadingCompleteListener onComplete, String url) {
          this.updateView=updateView;
          this.onComplete=onComplete;
          this.url=url;
        }

        @Override
        protected Bitmap doInBackground(URL... params) {
          try {
            URLConnection con = params[0].openConnection();
            // can use some more params, i.e. caching directory etc
            con.setUseCaches(true);
            this.urlInputStream = con.getInputStream();
            return BitmapFactory.decodeStream(urlInputStream);
          } catch (IOException e) {
            Log.w(UrlImageView.class.getName(), "failed to load image from " + params[0], e);
            return null;
          } finally {
            if (this.urlInputStream != null) {
              try {
                this.urlInputStream.close();
              } catch (IOException e) {
                ; // swallow
              } finally {
                this.urlInputStream = null;
              }
            }
          }
        }

        @Override
        protected void onPostExecute(Bitmap result) {
          if (!this.isCancelled) {
            // hope that call is thread-safe
              if(onComplete==null){
                  if(updateView!=null)
                  this.updateView.setImageBitmap(result);
              }else{
                  onComplete.onComplete(updateView, result);
              }
          }
          loadingList.remove(this);
        }

        /*
         * just remember that we were cancelled, no synchronization necessary
         */
        @Override
        protected void onCancelled() {
          this.isCancelled = true;
          try {
            if (this.urlInputStream != null) {
              try {
                this.urlInputStream.close();
              } catch (IOException e) {
                ;// swallow
              } finally {
                this.urlInputStream = null;
              }
            }
          } finally {
            super.onCancelled();
            if(onComplete!=null)
                onComplete.onCancel(updateView);
            loadingList.remove(this);
          }
        }
      }

}