Android从SD卡加载大量图片

来源：互联网发布：苏州ug编程培训编辑：程序博客网时间：2024/05/14 13:16

package com.exam.gallery;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Handler;import android.support.v4.util.LruCache;import android.widget.ImageView;/** * 从SDCard异步加载图片 * * @author hanj 2013-8-22 19:25:46 */public class SDCardImageLoader {    //缓存    private LruCache<String, Bitmap> imageCache;    // 固定2个线程来执行任务    private ExecutorService executorService = Executors.newFixedThreadPool(2);    private Handler handler = new Handler();    private int screenW, screenH;    public SDCardImageLoader(int screenW, int screenH) {        this.screenW = screenW;        this.screenH = screenH;        // 获取应用程序最大可用内存        int maxMemory = (int) Runtime.getRuntime().maxMemory();        int cacheSize = maxMemory / 8;        // 设置图片缓存大小为程序最大可用内存的1/8        imageCache = new LruCache<String, Bitmap>(cacheSize) {            @Override            protected int sizeOf(String key, Bitmap value) {                return value.getRowBytes() * value.getHeight();            }        };    }    private Bitmap loadDrawable(final int smallRate, final String filePath,                                final ImageCallback callback) {        // 如果缓存过就从缓存中取出数据        if (imageCache.get(filePath) != null) {            return imageCache.get(filePath);        }        // 如果缓存没有则读取SD卡        executorService.submit(new Runnable() {            public void run() {                try {                    BitmapFactory.Options opt = new BitmapFactory.Options();                    opt.inJustDecodeBounds = true;                    BitmapFactory.decodeFile(filePath, opt);                    // 获取到这个图片的原始宽度和高度                    int picWidth = opt.outWidth;                    int picHeight = opt.outHeight;                    //读取图片失败时直接返回                    if (picWidth == 0 || picHeight == 0) {                        return;                    }                    //初始压缩比例                    opt.inSampleSize = smallRate;                    // 根据屏的大小和图片大小计算出缩放比例                    if (picWidth > picHeight) {                        if (picWidth > screenW)                            opt.inSampleSize *= picWidth / screenW;                    } else {                        if (picHeight > screenH)                            opt.inSampleSize *= picHeight / screenH;                    }                    //这次再真正地生成一个有像素的，经过缩放了的bitmap                    opt.inJustDecodeBounds = false;                    final Bitmap bmp = BitmapFactory.decodeFile(filePath, opt);                    //存入map                    imageCache.put(filePath, bmp);                    handler.post(new Runnable() {                        public void run() {                            callback.imageLoaded(bmp);                        }                    });                } catch (Exception e) {                    e.printStackTrace();                }            }        });        return null;    }    /**     * 异步读取SD卡图片，并按指定的比例进行压缩（最大不超过屏幕像素数）     *     * @param smallRate 压缩比例，不压缩时输入1，此时将按屏幕像素数进行输出     * @param filePath  图片在SD卡的全路径     * @param imageView 组件     */    public void loadImage(int smallRate, final String filePath, final ImageView imageView) {        Bitmap bmp = loadDrawable(smallRate, filePath, new ImageCallback() {            @Override            public void imageLoaded(Bitmap bmp) {                if (imageView.getTag().equals(filePath)) {                    if (bmp != null) {                        imageView.setImageBitmap(bmp);                    } else {                        imageView.setImageResource(0);                    }                }            }        });        if (bmp != null) {            if (imageView.getTag().equals(filePath)) {                imageView.setImageBitmap(bmp);            }        } else {            imageView.setImageResource(0);        }    }    // 对外界开放的回调接口    public interface ImageCallback {        // 注意 此方法是用来设置目标对象的图像资源        public void imageLoaded(Bitmap imageDrawable);    }}

用法：

String path=list.get(position);holder.img.setTag(path);imageLoader.loadImage(2, path, holder.img);

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