android - Android 在 Listview 中加载更多图像

Question

我正在使用下面的 Url 食谱，但是当我经常运行应用程序时，它会导致内存不足问题（OOM），任何人都可以发送更新的 ImageLoader，它可以立即加载图像（拇指指甲）并保存到缓存中。提前致谢。 http://codehenge.net/blog/2011/06/android-development-tutorial-asynchronous-lazy-loading-and-caching-of-listview-images/

Answer 1

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.URL;
import java.util.HashMap;
import java.util.Stack;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.widget.ImageView;

public class ImageLoader {

    // the simplest in-memory cache implementation. This should be replaced with
    // something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
    private HashMap<String, Bitmap> cache = new HashMap<String, Bitmap>();

    private File cacheDir;
    private Context ctx;

    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);
        ctx = context;
        // Find the dir to save cached images
        if (android.os.Environment.getExternalStorageState().equals(
                android.os.Environment.MEDIA_MOUNTED))
            cacheDir = new File(
                    android.os.Environment.getExternalStorageDirectory(),
                    ".abcde");
        else
            cacheDir = context.getCacheDir();
        if (!cacheDir.exists())
            cacheDir.mkdirs();
    }

    final int stub_id = R.drawable.no_image;

    public void DisplayImage(String url, Activity activity, ImageView imageView) {
        if (cache.containsKey(url)) {

            imageView.setImageBitmap(cache.get(url));
        } else {
            queuePhoto(url, activity, imageView);
            imageView.setImageResource(stub_id);
        }
    }

    private void queuePhoto(String url, Activity activity, 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();
    }

    public Bitmap getBitmap(String urlString) {
        String filename = String.valueOf(urlString.substring(urlString
                .lastIndexOf("/") + 1));
        File f = new File(cacheDir, filename);
        try {
            if (!f.exists()) {
                Bitmap bitmap = null;
                InputStream is = new URL(urlString).openStream();
                OutputStream os = new FileOutputStream(f);
                Globals.CopyStream(is, os);
                os.close();
                bitmap = decodeFile(f);

                return bitmap;
            } else {
                Bitmap bitmap = decodeFile(f);
                return bitmap;
            }

        } catch (Exception ex) {
            ex.printStackTrace();
            Log.e(Data.LOG, ex.getMessage(), ex);
            Bitmap icon = BitmapFactory.decodeResource(ctx.getResources(),
                    R.drawable.no_image);
            return icon;
        }
    }

    // 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);

            // Find the correct scale value. It should be the power of 2.
            final int REQUIRED_SIZE = 70;
            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++;
            }

            // 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;
    }

    // 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 {
        @Override
        public void run() {
            try {
                while (true) {

                    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);
                        cache.put(photoToLoad.url, bmp);

                        if (photoToLoad.url == null) {

                        } else {

                            if (((String) photoToLoad.imageView.getTag())
                                    .equals(photoToLoad.url)) {
                                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)
                imageView.setImageBitmap(bitmap);
            else
                imageView.setImageResource(stub_id);
        }
    }

    public void clearCache() {

        cache.clear();

        // clear SD cache
        File[] files = cacheDir.listFiles();
        for (File f : files)
            f.delete();
    }

}