用于社交网络应用程序的来自服务器的 Android 画廊图像

Question

大家好，我正在寻找如何有效地将图像从服务器加载到我的图库中。现在我正在使用 this url 中解释的延迟加载技术

但是当图库图像的数量增加时它仍然会变慢。任何人都可以找到或使用任何其他技术吗？我也不明白一些社交网络应用程序如 POF 和 match.com 等是如何在图像最初显示为模糊并获得良好质量的情况下实现它们的。希望你们能理解我的问题。希望得到更好的答复。提前致谢。

编辑#1:

抱歉，我刚刚在上面粘贴了不同的 url... This is the one which i have followed for my implementation

也翻了第一个url，发现他们也用了同样的逻辑...

编辑#2:

gallery.setAdapter(new LazyGalleryBaseAdapter(this, mStrings)); 
imageLoader.DisplayImage(data[position], activity, image);// called from the getview method of LazyGalleryBaseAdapter class 

ImageLoader类如下:

package com.sdi.lazyimageloader;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Collections;
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.widget.ImageView;

import com.sdi.videodate.R;

public class ImageLoader {

MemoryCache memoryCache = new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews = Collections
        .synchronizedMap(new WeakHashMap<ImageView, String>());
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;
    fileCache = new FileCache(context);
}

final int stub_id = R.drawable.stub;

public void DisplayImage(String url, Activity activity, ImageView imageView) {
    imageViews.put(imageView, url);
    Bitmap bitmap = memoryCache.get(url);
    System.err.println("bitmap ??????"+bitmap);
    System.out.println("imageView ===> "+imageView);
    if (bitmap != null) {
        // call the below line to get the rounded corner image
//          Bitmap bitmap1 = LazyAdapter.getRoundedCornerBitmap(ctx, bitmap,
//                  7f, 7f, 7f, 7f, 85, 85);            

        imageView.setImageBitmap(bitmap);
    } else {
        queuePhoto(url, activity, imageView);
        imageView.setImageResource(stub_id);
        System.err.println("bitmap stub_id??????"+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();
}

private 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(30000);
        conn.setReadTimeout(30000);
        InputStream is = conn.getInputStream();
        OutputStream os = new FileOutputStream(f);
        Utils.CopyStream(is, os);
        os.close();
        bitmap = decodeFile(f);
        return bitmap;
    } catch (Exception ex) {
        ex.printStackTrace();
        return null;
    }
}

private static Bitmap decodeFiles(File f) {
    Bitmap b = null;
    try {
        // Decode image size
        int IMAGE_MAX_SIZE = 80;
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;

        FileInputStream fis = new FileInputStream(f);
        BitmapFactory.decodeStream(fis, null, o);
        try {
            fis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        int scale = 1;
        if (o.outHeight <= 1300 && o.outWidth <= 1000) {
            scale = 1;
        } else if (o.outHeight >= 1280 && o.outWidth >= 960) {
            scale = 6;
        } else if (o.outHeight > IMAGE_MAX_SIZE
                || o.outWidth > IMAGE_MAX_SIZE) {

            // scale = (int) Math.pow(2,(int)
            // Math.round(Math.log(IMAGE_MAX_SIZE / (double)
            // Math.max(o.outHeight, o.outWidth))/ Math.log(0.5)));
            scale = 5;
        }
        /*
         * else if (o.outHeight > IMAGE_MAX_SIZE || o.outWidth >
         * IMAGE_MAX_SIZE) { // scale = (int) Math.pow( 2,(int) //
         * Math.round(Math.log(IMAGE_MAX_SIZE / (double) //
         * Math.max(o.outHeight, o.outWidth))/ Math.log(0.5))); scale = 8; }
         */

        System.err.println(scale
                + "---Scale Value (((((((((((((((((((((((((((((("
                + o.outHeight + "---" + o.outWidth);

        // Decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        fis = new FileInputStream(f);
        try{
        b = BitmapFactory.decodeStream(fis, null, o2);
        }
        catch (OutOfMemoryError e) {
            // TODO: handle exception
        }
        try {
            fis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

    return b;
}

// decodes image and scales it to reduce memory consumption
/*
 * rename by dinash from decodeFile to decodeFiles
 */
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 *= 2;
        }

        // decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        try{
        return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        }
        catch (OutOfMemoryError e) {
            // TODO: handle exception
        }
    } 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 {
    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);
                    memoryCache.put(photoToLoad.url, bmp);
                    String tag = imageViews.get(photoToLoad.imageView);
                    if (tag != null && tag.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() {
        System.out.println("imageView ===> "+imageView);
        if (bitmap != null)
            imageView.setImageBitmap(bitmap);
        else
            imageView.setImageResource(stub_id);
    }
}

public void clearCache() {
    memoryCache.clear();
    fileCache.clear();
}

}

Answer 1

据我了解，您正在使用我的实现 https://github.com/thest1/LazyList .如果你得到最新的代码，你可以看到我修改了它以使用线程池。所以现在它同时下载多张图片。试试这个演示，它现在真的很快。

您还谈到了模糊图像。当您有可用的缩略图并且在下载全尺寸图像时可以模糊显示时，通常会发生这种情况。如果您没有缩略图，则没有什么可模糊的。