将图像从图像URL下载到图像视图

Question

i am trying to download image from imageurl the image comming from that url is a high resolution image.it is working fine in all high resolution phones when i tried to load this image in to a an emulator of mdpi it is throwing out of memory leak exception.

how can i handle this situation and i want this image in each and every screen so i am declaring bitmap as a global variable

is there any way to reduce the image size while downloading. iam using the below code to download an image

c1 is the reference to image view

bitmap = BitmapFactory.decodeStream((InputStream)new URL(logourltop.get(0)).getContent());
cl.setImageBitmap(bitmap) ;

(or)

it is better to use urlimagehelper project to download an image whenever required

UrlImageViewHelper.setUrlDrawable(cl,logourltop.get(0));

and one more doubt is i am changing the views in the same activity by using

setContentView(R.layout.filename).

if i change the view on listitem click the memory allocated for the bitmap will be released or not.(The memory allocated for objects and bitmaps for that view)

can you please suggest me a better way to avoid memory leaks.

Answer 1

You basically have to download the image data and with the image data in form of a stream or a byte array, you can use the convenience methods from BitmapFactory that will give you a Bitmap out of it, and with this Bitmap in hands, you can already set it directly to the ImageView.

Make sure you perform the download from the network in a separated Thread eg using AsyncTask .doInBackground() and set the Bitmap on the ImageView on the UI thread eg by setting it on the method onPostExecute() of the AsyncTask or calling Activity.runOnUIThread() .

Answer 2

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URL;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ImageView;

public class downloadimg extends Activity {

//  
private ImageView mImageView;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    //Find the reference to the ImageView
    mImageView = (ImageView) findViewById(R.id.test_image);

    // You can set a temporary background here
    //image.setImageResource(null);

    // Start the DownloadImage task with the given url
    new DownloadImage().execute("http://demo.imgur.com/CQzlM.jpg");
}


/**
 * Simple functin to set a Drawable to the image View
 * @param drawable
 */
private void setImage(Drawable drawable)
{
    mImageView.setBackgroundDrawable(drawable);
}

public class DownloadImage extends AsyncTask<String, Integer, Drawable> {

    @Override
    protected Drawable doInBackground(String... arg0) {
        // This is done in a background thread
        return downloadImage(arg0[0]);
    }

    /**
     * Called after the image has been downloaded
     * -> this calls a function on the main thread again
     */
    protected void onPostExecute(Drawable image)
    {
        setImage(image);
    }


    /**
     * Actually download the Image from the _url
     * @param _url
     * @return
     */
    private Drawable downloadImage(String _url)
    {
        //Prepare to download image
        URL url;        
        BufferedOutputStream out;
        InputStream in;
        BufferedInputStream buf;

        //BufferedInputStream buf;
        try {
            url = new URL(_url);
            in = url.openStream();



            // Read the inputstream 
            buf = new BufferedInputStream(in);

            // Convert the BufferedInputStream to a Bitmap
            Bitmap bMap = BitmapFactory.decodeStream(buf);
            if (in != null) {
                in.close();
            }
            if (buf != null) {
                buf.close();
            }

            return new BitmapDrawable(bMap);

        } catch (Exception e) {
            Log.e("Error reading file", e.toString());
        }

        return null;
    }

}

}

Answer 3

Hope this will help...

public class BitmapResizer {

    public static Bitmap decodeFile(File f,int requiredSize){
    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=requiredSize;
        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;
}}