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Android图片管理组件（双缓存+异步加载）

2024-07-18 08:18:38   230人阅读

转自：http://www.oschina.net/code/snippet_219356_18887?p=3#comments

 

ImageManager2这个类具有异步从网络下载图片，从sd读取本地图片，内存缓存，硬盘缓存，图片使用动画渐现等功能，已经将其应用在包含大量图片的应用中一年多，没有出现oom

Android程序常常会内存溢出，网上也有很多解决方案，如软引用，手动调用recycle等等。但经过我们实践发现这些方案，都没能起到很好的效果，我们的应用依然会出现很多oom，尤其我们的应用包含大量的图片。android3.0之后软引用基本已经失效，因为虚拟机只要碰到软引用就回收，所以带不来任何性能的提升。

我这里的解决方案是HandlerThread(异步加载)+LruCache(内存缓存)+DiskLruCache(硬盘缓存)。

作为程序员，我也不多说，直接和大家共享我的代码，用代码交流更方便些。

源码demo地址：https://github.com/yueyueniao2012/multiimagechooser

标签： <无>

代码片段(1) [全屏查看所有代码]

1. [文件] ImageManager2.java ~ 13KB     下载(468)    

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package com.example.util;
 
import java.io.File;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
 
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.util.EntityUtils;
 
import android.app.ActivityManager;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.TransitionDrawable;
import android.media.ThumbnailUtils;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.os.Message;
import android.support.v4.util.LruCache;
import android.widget.ImageView;
 
import com.example.MyApplication;
 
/**
 * 图片加载类
 *
 * @author 月月鸟
 */
public class ImageManager2 {
 
    private static ImageManager2 imageManager;
    public LruCache<String, Bitmap> mMemoryCache;
    private static final int DISK_CACHE_SIZE = 1024 * 1024 * 20; // 10MB
    private static final String DISK_CACHE_SUBDIR = "thumbnails";
    public DiskLruCache mDiskCache;
    private static MyApplication myapp;
 
    /** 图片加载队列，后进先出 */
    private Stack<ImageRef> mImageQueue = new Stack<ImageRef>();
 
    /** 图片请求队列，先进先出，用于存放已发送的请求。 */
    private Queue<ImageRef> mRequestQueue = new LinkedList<ImageRef>();
 
    /** 图片加载线程消息处理器 */
    private Handler mImageLoaderHandler;
 
    /** 图片加载线程是否就绪 */
    private boolean mImageLoaderIdle = true;
 
    /** 请求图片 */
    private static final int MSG_REQUEST = 1;
    /** 图片加载完成 */
    private static final int MSG_REPLY = 2;
    /** 中止图片加载线程 */
    private static final int MSG_STOP = 3;
    /** 如果图片是从网络加载，则应用渐显动画，如果从缓存读出则不应用动画 */
    private boolean isFromNet = true;
 
    /**
     * 获取单例，只能在UI线程中使用。
     *
     * @param context
     * @return
     */
    public static ImageManager2 from(Context context) {
 
        // 如果不在ui线程中，则抛出异常
        if (Looper.myLooper() != Looper.getMainLooper()) {
            throw new RuntimeException("Cannot instantiate outside UI thread.");
        }
 
        if (myapp == null) {
            myapp = (MyApplication) context.getApplicationContext();
        }
 
        if (imageManager == null) {
            imageManager = new ImageManager2(myapp);
        }
 
        return imageManager;
    }
 
    /**
     * 私有构造函数，保证单例模式
     *
     * @param context
     */
    private ImageManager2(Context context) {
        int memClass = ((ActivityManager) context
                .getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();
        memClass = memClass > 32 ? 32 : memClass;
        // 使用可用内存的1/8作为图片缓存
        final int cacheSize = 1024 * 1024 * memClass / 8;
 
        mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {
 
            protected int sizeOf(String key, Bitmap bitmap) {
                return bitmap.getRowBytes() * bitmap.getHeight();
            }
 
        };
 
        File cacheDir = DiskLruCache
                .getDiskCacheDir(context, DISK_CACHE_SUBDIR);
        mDiskCache = DiskLruCache.openCache(context, cacheDir, DISK_CACHE_SIZE);
 
    }
 
    /**
     * 存放图片信息
     */
    class ImageRef {
 
        /** 图片对应ImageView控件 */
        ImageView imageView;
        /** 图片URL地址 */
        String url;
        /** 图片缓存路径 */
        String filePath;
        /** 默认图资源ID */
        int resId;
        int width = 0;
        int height = 0;
 
        /**
         * 构造函数
         *
         * @param imageView
         * @param url
         * @param resId
         * @param filePath
         */
        ImageRef(ImageView imageView, String url, String filePath, int resId) {
            this.imageView = imageView;
            this.url = url;
            this.filePath = filePath;
            this.resId = resId;
        }
 
        ImageRef(ImageView imageView, String url, String filePath, int resId,
                int width, int height) {
            this.imageView = imageView;
            this.url = url;
            this.filePath = filePath;
            this.resId = resId;
            this.width = width;
            this.height = height;
        }
 
    }
 
    /**
     * 显示图片
     *
     * @param imageView
     * @param url
     * @param resId
     */
    public void displayImage(ImageView imageView, String url, int resId) {
        if (imageView == null) {
            return;
        }
        if (imageView.getTag() != null
                && imageView.getTag().toString().equals(url)) {
            return;
        }
        if (resId >= 0) {
            if (imageView.getBackground() == null) {
                imageView.setBackgroundResource(resId);
            }
            imageView.setImageDrawable(null);
 
        }
        if (url == null || url.equals("")) {
            return;
        }
 
        // 添加url tag
        imageView.setTag(url);
 
        // 读取map缓存
        Bitmap bitmap = mMemoryCache.get(url);
        if (bitmap != null) {
            setImageBitmap(imageView, bitmap, false);
            return;
        }
 
        // 生成文件名
        String filePath = urlToFilePath(url);
        if (filePath == null) {
            return;
        }
 
        queueImage(new ImageRef(imageView, url, filePath, resId));
    }
 
    /**
     * 显示图片固定大小图片的缩略图，一般用于显示列表的图片，可以大大减小内存使用
     *
     * @param imageView 加载图片的控件
     * @param url 加载地址
     * @param resId 默认图片
     * @param width 指定宽度
     * @param height 指定高度
     */
    public void displayImage(ImageView imageView, String url, int resId,
            int width, int height) {
        if (imageView == null) {
            return;
        }
        if (resId >= 0) {
 
            if (imageView.getBackground() == null) {
                imageView.setBackgroundResource(resId);
            }
            imageView.setImageDrawable(null);
 
        }
        if (url == null || url.equals("")) {
            return;
        }
 
        // 添加url tag
        imageView.setTag(url);
        // 读取map缓存
        Bitmap bitmap = mMemoryCache.get(url + width + height);
        if (bitmap != null) {
            setImageBitmap(imageView, bitmap, false);
            return;
        }
 
        // 生成文件名
        String filePath = urlToFilePath(url);
        if (filePath == null) {
            return;
        }
 
        queueImage(new ImageRef(imageView, url, filePath, resId, width, height));
    }
 
    /**
     * 入队，后进先出
     *
     * @param imageRef
     */
    public void queueImage(ImageRef imageRef) {
 
        // 删除已有ImageView
        Iterator<ImageRef> iterator = mImageQueue.iterator();
        while (iterator.hasNext()) {
            if (iterator.next().imageView == imageRef.imageView) {
                iterator.remove();
            }
        }
 
        // 添加请求
        mImageQueue.push(imageRef);
        sendRequest();
    }
 
    /**
     * 发送请求
     */
    private void sendRequest() {
 
        // 开启图片加载线程
        if (mImageLoaderHandler == null) {
            HandlerThread imageLoader = new HandlerThread("image_loader");
            imageLoader.start();
            mImageLoaderHandler = new ImageLoaderHandler(
                    imageLoader.getLooper());
        }
 
        // 发送请求
        if (mImageLoaderIdle && mImageQueue.size() > 0) {
            ImageRef imageRef = mImageQueue.pop();
            Message message = mImageLoaderHandler.obtainMessage(MSG_REQUEST,
                    imageRef);
            mImageLoaderHandler.sendMessage(message);
            mImageLoaderIdle = false;
            mRequestQueue.add(imageRef);
        }
    }
 
    /**
     * 图片加载线程
     */
    class ImageLoaderHandler extends Handler {
 
        public ImageLoaderHandler(Looper looper) {
            super(looper);
        }
 
        public void handleMessage(Message msg) {
            if (msg == null)
                return;
 
            switch (msg.what) {
 
            case MSG_REQUEST: // 收到请求
                Bitmap bitmap = null;
                Bitmap tBitmap = null;
                if (msg.obj != null && msg.obj instanceof ImageRef) {
 
                    ImageRef imageRef = (ImageRef) msg.obj;
                    String url = imageRef.url;
                    if (url == null)
                        return;
                    // 如果本地url即读取sd相册图片，则直接读取，不用经过DiskCache
                    if (url.toLowerCase().contains("dcim")) {
 
                        tBitmap = null;
                        BitmapFactory.Options opt = new BitmapFactory.Options();
                        opt.inSampleSize = 1;
                        opt.inJustDecodeBounds = true;
                        BitmapFactory.decodeFile(url, opt);
                        int bitmapSize = opt.outHeight * opt.outWidth * 4;
                        opt.inSampleSize = bitmapSize / (1000 * 2000);
                        opt.inJustDecodeBounds = false;
                        tBitmap = BitmapFactory.decodeFile(url, opt);
                        if (imageRef.width != 0 && imageRef.height != 0) {
                            bitmap = ThumbnailUtils.extractThumbnail(tBitmap,
                                    imageRef.width, imageRef.height,
                                    ThumbnailUtils.OPTIONS_RECYCLE_INPUT);
                            isFromNet = true;
                        } else {
                            bitmap = tBitmap;
                            tBitmap = null;
                        }
 
                    } else
                        bitmap = mDiskCache.get(url);
 
                    if (bitmap != null) {
                        // ToolUtil.log("从disk缓存读取");
                        // 写入map缓存
                        if (imageRef.width != 0 && imageRef.height != 0) {
                            if (mMemoryCache.get(url + imageRef.width
                                    + imageRef.height) == null)
                                mMemoryCache.put(url + imageRef.width
                                        + imageRef.height, bitmap);
                        } else {
                            if (mMemoryCache.get(url) == null)
                                mMemoryCache.put(url, bitmap);
                        }
 
                    } else {
                        try {
                            byte[] data = http://www.mamicode.com/loadByteArrayFromNetwork(url);
 
                            if (data != null) {
 
                                BitmapFactory.Options opt = new BitmapFactory.Options();
                                opt.inSampleSize = 1;
 
                                opt.inJustDecodeBounds = true;
                                BitmapFactory.decodeByteArray(data, 0,
                                        data.length, opt);
                                int bitmapSize = opt.outHeight * opt.outWidth
                                        * 4;// pixels*3 if it‘s RGB and pixels*4
                                            // if it‘s ARGB
                                if (bitmapSize > 1000 * 1200)
                                    opt.inSampleSize = 2;
                                opt.inJustDecodeBounds = false;
                                tBitmap = BitmapFactory.decodeByteArray(data,
                                        0, data.length, opt);
                                if (imageRef.width != 0 && imageRef.height != 0) {
                                    bitmap = ThumbnailUtils
                                            .extractThumbnail(
                                                    tBitmap,
                                                    imageRef.width,
                                                    imageRef.height,
                                                    ThumbnailUtils.OPTIONS_RECYCLE_INPUT);
                                } else {
                                    bitmap = tBitmap;
                                    tBitmap = null;
                                }
 
                                if (bitmap != null && url != null) {
                                    // 写入SD卡
                                    if (imageRef.width != 0
                                            && imageRef.height != 0) {
                                        mDiskCache.put(url + imageRef.width
                                                + imageRef.height, bitmap);
                                        mMemoryCache.put(url + imageRef.width
                                                + imageRef.height, bitmap);
                                    } else {
                                        mDiskCache.put(url, bitmap);
                                        mMemoryCache.put(url, bitmap);
                                    }
                                    isFromNet = true;
                                }
                            }
                        } catch (OutOfMemoryError e) {
                        }
 
                    }
 
                }
 
                if (mImageManagerHandler != null) {
                    Message message = mImageManagerHandler.obtainMessage(
                            MSG_REPLY, bitmap);
                    mImageManagerHandler.sendMessage(message);
                }
                break;
 
            case MSG_STOP: // 收到终止指令
                Looper.myLooper().quit();
                break;
 
            }
        }
    }
 
    /** UI线程消息处理器 */
    private Handler mImageManagerHandler = new Handler() {
 
        @Override
        public void handleMessage(Message msg) {
            if (msg != null) {
                switch (msg.what) {
 
                case MSG_REPLY: // 收到应答
 
                    do {
                        ImageRef imageRef = mRequestQueue.remove();
 
                        if (imageRef == null)
                            break;
 
                        if (imageRef.imageView == null
                                || imageRef.imageView.getTag() == null
                                || imageRef.url == null)
                            break;
 
                        if (!(msg.obj instanceof Bitmap) || msg.obj == null) {
                            break;
                        }
                        Bitmap bitmap = (Bitmap) msg.obj;
 
                        // 非同一ImageView
                        if (!(imageRef.url).equals((String) imageRef.imageView
                                .getTag())) {
                            break;
                        }
 
                        setImageBitmap(imageRef.imageView, bitmap, isFromNet);
                        isFromNet = false;
 
                    } while (false);
 
                    break;
                }
            }
            // 设置闲置标志
            mImageLoaderIdle = true;
 
            // 若服务未关闭，则发送下一个请求。
            if (mImageLoaderHandler != null) {
                sendRequest();
            }
        }
    };
 
    /**
     * 添加图片显示渐现动画
     *
     */
    private void setImageBitmap(ImageView imageView, Bitmap bitmap,
            boolean isTran) {
        if (isTran) {
            final TransitionDrawable td = new TransitionDrawable(
                    new Drawable[] {
                            new ColorDrawable(android.R.color.transparent),
                            new BitmapDrawable(bitmap) });
            td.setCrossFadeEnabled(true);
            imageView.setImageDrawable(td);
            td.startTransition(300);
        } else {
            imageView.setImageBitmap(bitmap);
        }
    }
 
    /**
     * 从网络获取图片字节数组
     *
     * @param url
     * @return
     */
    private byte[] loadByteArrayFromNetwork(String url) {
 
        try {
 
            HttpGet method = new HttpGet(url);
            HttpResponse response = myapp.getHttpClient().execute(method);
            HttpEntity entity = response.getEntity();
            return EntityUtils.toByteArray(entity);
 
        } catch (Exception e) {
            return null;
        }
 
    }
 
    /**
     * 根据url生成缓存文件完整路径名
     *
     * @param url
     * @return
     */
    public String urlToFilePath(String url) {
 
        // 扩展名位置
        int index = url.lastIndexOf(‘.‘);
        if (index == -1) {
            return null;
        }
 
        StringBuilder filePath = new StringBuilder();
 
        // 图片存取路径
        filePath.append(myapp.getCacheDir().toString()).append(‘/‘);
 
        // 图片文件名
        filePath.append(MD5.Md5(url)).append(url.substring(index));
 
        return filePath.toString();
    }
 
    /**
     * Activity#onStop后，ListView不会有残余请求。
     */
    public void stop() {
 
        // 清空请求队列
        mImageQueue.clear();
 
    }
 
}
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  • 41楼：木法沙王 发表于 2014-04-10 17:26 回复此评论
    //如果本地url即读取sd相册图片，则直接读取，不用经过DiskCache
    if (url.toLowerCase().contains("dcim")
    建议把dcim改为mnt, 这样别的路经下图片也能加载了
  • 42楼：迷途的小羔羊 发表于 2014-05-02 16:14 回复此评论
    我他妈的非常感谢你，真心的
  • 43楼：wgggfiy 发表于 2014-06-05 10:56 回复此评论
    请问这个缓存何时可以清空呢？？我担心内存和磁盘会慢慢越积越大
  • 44楼：巴顿将军 发表于 2014-07-19 18:16 回复此评论
    什么东西呀，我跑不起来，看不到什么效果呢
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