如何从自定义适配器动态设置列表视图的imageView源？

Question

I'm trying to set an imageView source based on a string within a custom ArrayAdapter, but I'm unable to get it to work. I know the object rec_gift is coming through correctly and the icon_string variable get's the correct name, but the setImageResource call isn't working.

public class MySimpleArrayAdapter extends ArrayAdapter<Gift> {
  private final Context context;
  private List<Gift> giftz2;

  public MySimpleArrayAdapter(Context context, List<Gift> giftx) {
        super(context, R.layout.listview_rowlayout, giftx);
    this.context = context;
        this.giftz2 = giftx;
      }

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View rowView = inflater.inflate(R.layout.listview_rowlayout, parent, false);

    ImageView iconz = (ImageView) rowView.findViewById(R.id.icon);

    Gift rec_gift = (Gift) getItem(position);

    String icon_string = "R.drawable." + rec_gift.photo_key;

    iconz.setImageResource(getImageId(icon_string));

    return rowView;
  }

  public int getImageId(String imageName) {
        return context.getResources().getIdentifier("drawable/" + imageName, null, context.getPackageName());
    }
} 

In the above code, I want to set the imageView based on the icon_string variable so each row in the listView will get the correct image but it's not making a change at all.

Answer 1

Implement getItem method of your custom adapter:

@Override
public Gift getItem(int position) {
    if(this.giftz2 != null) {
        this.giftz2.get(position);
    } else {
        return null;
    }
}

And change this:

public int getImageId(String imageName) {
    return context.getResources().getIdentifier("drawable/" + imageName, null, context.getPackageName());
}

To this:

public int getImageId(String imageName) {
    return context.getResources().getIdentifier(imageName, "drawable", context.getPackageName());
}

And call method:

String icon_string = String.valueOf(rec_gift.photo_key);
iconz.setImageResource(getImageId(icon_string));

BTW: Try to reuse your views at your adapters getView method. If you continue using your implementation, you are going to get memory errors.

Answer 2

if you are trying to download image from web service and setting that image in imageview then you may use image loader

put this line in your adapter where you want to display image and pass the parameters

ImageLoader_class(image_url, image_view , progressbar);

// new creat a class with the name of ImageLoader_class and paste this code in that

    import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Stack;


import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Path;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.view.View;
import android.widget.ImageView;
import android.widget.ProgressBar;




public class ImageLoader_class{
    private static MemoryCache memoryCache = new MemoryCache();
    // private static FileCache fileCache;
    private static boolean isImageLoaderClass = true;
    private static ImageLoader_circle_img imageLoader = null;
    final static int stub_id = R.drawable.ic_launcher;
    private static Bitmap defaultBitmap = null;
    private static Context mContext;

    /**
     * This is constructor of ImageLoader Class make the background thread low
     * priority. This way it will not affect the UI performance *
     * 
     * @param mContext
     *            application context
     */
    private ImageLoader_circle_img(Context context) {
        mContext = context;

        photoLoaderThread.setPriority(Thread.NORM_PRIORITY - 1);

        // fileCache = new FileCache(mContext);
    }

    /**
     * This Method is used to implement singleton concept in this class
     * 
     * @param context
     *            application context
     * @return Class object of this class
     */
    public static ImageLoader_circle_img getInstanceImageLoader(Context context) {
        if (isImageLoaderClass) {
            isImageLoaderClass = false;
            imageLoader = new ImageLoader_circle_img(context);
            return imageLoader;
        }
        return imageLoader;
    }

    /**
     * This method is used to set image in image view
     * 
     * @param url
     *            from this URL, image will be down-load
     * @param imageView
     *            in this view set the image bitmap
     * @param progressBar
     *            which is show when image is displaying
     */

    @SuppressWarnings("deprecation")
    public static void DisplayImage(String url, ImageView imageView,
            ProgressBar progressBar) {

        if (url == null || url.equals("")) {
            imageView.setVisibility(View.VISIBLE);
            // imageView.setImageBitmap(getDefaultBitmap());
            imageView.setBackgroundDrawable(new BitmapDrawable(
                    getDefaultBitmap()));
            progressBar.setVisibility(View.INVISIBLE);


        } else if (memoryCache.get(url) != null) {
            imageView.setVisibility(View.VISIBLE);
            // imageView.setImageBitmap(memoryCache.get(url));
            imageView.setBackgroundDrawable(new BitmapDrawable(memoryCache
                    .get(url)));
            progressBar.setVisibility(View.INVISIBLE);

        } else {
            queuePhoto(url, imageView, progressBar);
            System.out.println("url"+url);
        }
    }
    public static Bitmap getRoundedShape(Bitmap scaleBitmapImage) {
        // TODO Auto-generated method stub
        int targetWidth = 100;
        int targetHeight = 100;
        Bitmap targetBitmap = Bitmap.createBitmap(targetWidth, targetHeight,
                Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(targetBitmap);
        Path path = new Path();
        path.addCircle(((float) targetWidth - 1) / 2,
                ((float) targetHeight - 1) / 2,
                (Math.min(((float) targetWidth), ((float) targetHeight)) / 2),
                Path.Direction.CCW);

        canvas.clipPath(path);
        Bitmap sourceBitmap = scaleBitmapImage;
        canvas.drawBitmap(sourceBitmap, new Rect(0, 0, sourceBitmap.getWidth(),
                sourceBitmap.getHeight()), new Rect(0, 0, targetWidth,
                targetHeight), null);
        return targetBitmap;
    }
    /**
     * this method is used to get default bitmap if image url is null
     * 
     * @return bitmap
     */

    private static Bitmap getDefaultBitmap() {
        try {
            defaultBitmap = BitmapFactory.decodeResource(mContext
                    .getResources(), stub_id);
            int width = defaultBitmap.getWidth();
            int height = defaultBitmap.getHeight();
            return Bitmap.createScaledBitmap(defaultBitmap, width / 4,
                    height / 4, true);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * If bitmap is not downloaded then add in queue
     * 
     * @param url
     *            from this URL, image will be down-load
     * @param imageView
     *            in this view set the image bitmap
     * @param progressBar
     *            which is show when image is displaying
     */
    private static void queuePhoto(String url, ImageView imageView,
            ProgressBar progressBar) {
        photosQueue.Clean(imageView);
        PhotoToLoad p = new PhotoToLoad(url, imageView, progressBar);
        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();
    }

    /**
     * this method is used to download bitmap
     * 
     * @param url
     *            from this URL, image will be down-load
     * @return bitmap
     */
    private static Bitmap getBitmap(String url) {

        URL myFileUrl = null;
        Bitmap bmImg = null;
        try {
            myFileUrl = new URL(url);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
        try {
            HttpURLConnection conn = (HttpURLConnection) myFileUrl
                    .openConnection();
            conn.setDoInput(true);
            conn.connect();
            InputStream is = conn.getInputStream();
            bmImg = BitmapFactory.decodeStream(is);

        } catch (IOException e) {
            e.printStackTrace();
        }
        if (bmImg != null)


        System.out.println(" bmImg.getWidth()"+ bmImg.getWidth());

        if(bmImg.getWidth()>300)
        {
            bmImg = Bitmap.createScaledBitmap(bmImg, bmImg.getWidth(),
                    bmImg.getHeight() , true);

        //  bmImg = Bitmap.createScaledBitmap(bmImg, bmImg.getWidth() / 4,
            //      bmImg.getHeight() / 4, true);
            System.out.println("IF STAT");
        }
        else
        {
            bmImg = Bitmap.createScaledBitmap(bmImg, 55,
                    55, true);

        }
        //Bitmap bt = ((BitmapDrawable) imageView.getDrawable()).getBitmap();
        //imageView.setImageBitmap(getRoundedShape(bmImg));
        //if the image needed in round shape
        //return getRoundedShape(bmImg);
        return bmImg;
    }

    /**
     * This class is used to manage url, imageview and progressBar
     */
    private static class PhotoToLoad {
        public String url;
        public ImageView imageView;
        public ProgressBar view;

        public PhotoToLoad(String u, ImageView i, ProgressBar v) {
            url = u;
            imageView = i;
            view = v;
        }
    }

    private static PhotosQueue photosQueue = new PhotosQueue();

    private static void stopThread() {
        photoLoaderThread.interrupt();
    }

    /**
     * this class is used to store list of photoes
     */
    private static 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;
            }
        }
    }

    /**
     * This thread is used to set photoes in imageView
     */
    private static class PhotosLoader extends Thread {
        @Override
        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;
                        try {
                            bmp = getBitmap(photoToLoad.url);
                            memoryCache.put(photoToLoad.url, bmp);
                            if (((String) photoToLoad.imageView.getTag()).equals(photoToLoad.url)) {
                                BitmapDisplayer bd = new BitmapDisplayer(bmp,
                                        photoToLoad.imageView, photoToLoad.view);
                                Activity a = (Activity) photoToLoad.imageView
                                        .getContext();
                                a.runOnUiThread(bd);
                            }
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                    if (Thread.interrupted())
                        break;
                }
            } catch (InterruptedException e) {
                // allow thread to exit
            }
        }
    }

    private static PhotosLoader photoLoaderThread = new PhotosLoader();

    /**
     * Used to display bitmap in the UI thread
     */
    private static class BitmapDisplayer implements Runnable {
        Bitmap bitmap;
        ImageView imageView;
        ProgressBar view;

        public BitmapDisplayer(Bitmap b, ImageView i, ProgressBar v) {
            bitmap = b;
            imageView = i;
            view = v;
        }

        @SuppressWarnings("deprecation")
        public void run() {
            if (bitmap != null) {
                imageView.setVisibility(View.VISIBLE);
                // imageView.setImageBitmap(bitmap);
                imageView.setBackgroundDrawable(new BitmapDrawable(bitmap));

                view.setVisibility(View.INVISIBLE);
            }
        }
    }

    /**
     * this function is used to clear all stored data
     */
    public static void clearCache() {
        stopThread();

        // clear memory cache
        memoryCache.clear();

        // clear SD cache
        /*
         * if (fileCache != null) { fileCache.clear(); }
         */
    }
}