图片三级缓存

直接上代码

ImageCache.java

public class ImageCache {

    // 一级缓存 内部是LinkedHashMap
    private LruCache<String, Bitmap> cache = null;

    // 使用线程池
    private ExecutorService threadPool = null;
    private File localDir = null;

    public ImageCache(Context context) {
        threadPool = Executors.newFixedThreadPool(5);
        localDir = context.getCacheDir();// 缓存目录
        // 1/8 100M
        long maxSize = Runtime.getRuntime().maxMemory() / 8;
        // 图片大小
        cache = new LruCache<String, Bitmap>((int) maxSize) {
            // 图片大小的计算规则
            @Override
            protected int sizeOf(String key, Bitmap value) {
                // // TODO Auto-generated method stub
                // return super.sizeOf(key, value);
                int bytesRow = value.getRowBytes();
                int rowCount = value.getHeight();
                return bytesRow * rowCount;
            }
        };
    }

    // http://a.hiphotos.baidu.com/image/w%3D310/sign=35424e84143853438ccf8120a312b01f/e61190ef76c6a7efce7315cef9faaf51f2de6684.jpg
    public void disPlayImage(ImageView imageView, String url) {
        //
        // ①　访问 集合 HashMap<url,Bitmap> 比LinkedhashMap LRUCache 设计最大值 100M(
        // 超过设置内存 丢弃 访问比较少的图片 )
        // ②　访问sd/cache
        // ③　访问 网络
        Bitmap bitmap = getFromCache(url);
        if (bitmap != null) {
            Log.i("wzx", "从内存取得图片");
            imageView.setImageBitmap(bitmap);
            return;
        }
        bitmap = getFromLocal(url);
        if (bitmap != null) {
            Log.i("wzx", "从本地取得图片");
            imageView.setImageBitmap(bitmap);
            return;
        }
        getFromNet(imageView, url);
        return;
    }

    private class ImageRunnable implements Runnable {

        private String url;

        private ImageView imageView;

        public ImageRunnable(ImageView imageView, String url) {
            super();
            this.imageView = imageView;
            this.url = url;
        }

        @Override
        public void run() {
            try {
                // TODO Auto-generated method stub
                // 在线程内存访问网络 HttpURLConnection
                // 拿到一个流
                URL urlObj = new URL(url);
                // 生成Bitmap
                HttpURLConnection conn = (HttpURLConnection) urlObj.openConnection();
                conn.setRequestMethod("GET");
                conn.setConnectTimeout(5000);
                if (200 == conn.getResponseCode()) {
                    InputStream input = conn.getInputStream();
                    // 使用工具快速生成bitmap对象
                    byte[] bytes = StreamUtils.readInputStream(input);
                    // Bitmap bitmap = BitmapFactory.decodeStream(input);
                    Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);

                    if (bitmap != null) {

                        Message msg = new Message();
                        msg.what = 200;
                        HashMap<String, Object> data = new HashMap<String, Object>();
                        data.put("imagview", imageView);// 停止出现图片错乱问题
                        data.put("bitmap", bitmap);
                        msg.obj = data;
                        handler.sendMessage(msg);// -->handlemesssage();
                        // Log.i("wzx", "imageview");
                        // Log.i("wzx", "gridview");
                        // Log.i("wzx", "listview");
                        // 保存到集合
                        cache.put(url, bitmap);
                        // 保存到文件目录
                        writeToLocal(url, bitmap);

                    }
                    return;

                }
            } catch (Exception e) {
                // TODO: handle exception
            }

            Message msg = new Message();
            msg.what = 404;
            handler.sendMessage(msg);
        }

    }

    private Handler handler = new Handler() {
        public void handleMessage(Message msg) {
            if (msg.what == 200) {
                HashMap<String, Object> data = (HashMap<String, Object>) msg.obj;
                ImageView imageView = (ImageView) data.get("imagview");
                Bitmap bitmap = (Bitmap) data.get("bitmap");
                imageView.setImageBitmap(bitmap);
            }
        };
    };

    // 把图片保存成文件
    private void writeToLocal(String url, Bitmap bitmap) {
        try {
            String rightFileName = URLEncoder.encode(url, "utf-8");
            File imgeFile = new File(localDir.getAbsolutePath() + "/" + rightFileName);
            if (!imgeFile.exists()) {
                imgeFile.createNewFile();
            }
            // 打开一个输出流 往里面写数据
            FileOutputStream fos = new FileOutputStream(imgeFile);
            // bitmap.compress(格式 jpg png, quality, 输出流);//将图片数据写入到一个文件输出流
            bitmap.compress(CompressFormat.JPEG, 80, fos);// 将图片数据写入到一个文件输出流
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void getFromNet(ImageView imageView, String url) {
        ImageRunnable r = new ImageRunnable(imageView, url);
        // 获 取一个线程
        threadPool.execute(r);

    }

    // 从本地文件获取图片
    private Bitmap getFromLocal(String url) {
        // data/data/包名/cache
        // linux http://www.baidu.com/1.jpg
        try {// %ss%dd
            String rightFileName = URLEncoder.encode(url, "utf-8");
            File imgeFile = new File(localDir.getAbsolutePath() + "/" + rightFileName);
            // 使用图片工具类 BitmapFratory 将文件转换成图片
            Bitmap bitmap = BitmapFactory.decodeFile(imgeFile.getAbsolutePath());
            // 为了下次访问提高速度 添加到集合中
            cache.put(url, bitmap);
            return bitmap;
        } catch (Exception e) {
            // TODO: handle exception
        }
        return null;
    }

    // 从集合取
    private Bitmap getFromCache(String url) {
        return cache.get(url);
    }

}

StreamUtils

public class StreamUtils {
    /**
     * 把一个流里面的内容 转化成一个字符串
     * 
     * @param is
     *            流里面的内容
     * @return null解析失败
     */
    public static String readStream(InputStream is) {
        try {
            byte[] bytes = readInputStream(is);
            return new String(bytes);
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static byte[] readInputStream(InputStream is) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len = -1;
        while ((len = is.read(buffer)) != -1) {
            baos.write(buffer, 0, len);
        }
        is.close();
        return baos.toByteArray();
    }
}

MainActivity

public class MainActivity extends Activity {
    String url1 = "https://ss0.baidu.com/7Po3dSag_xI4khGko9WTAnF6hhy/image/h%3D300/sign=ada3d2a50cd162d99aee641c21dea950/b7003af33a87e9509a816f0d16385343fbf2b439.jpg";
    String url2 = "https://ss1.baidu.com/9vo3dSag_xI4khGko9WTAnF6hhy/image/h%3D200/sign=e3cf61f8ba096b639e1959503c328733/203fb80e7bec54e7df58bcc9bd389b504ec26ab5.jpg";
    String url3 = "https://ss1.baidu.com/-4o3dSag_xI4khGko9WTAnF6hhy/image/h%3D200/sign=1ee684a4e6fe9925d40c6e5004a95ee4/8694a4c27d1ed21b2a3bb284ab6eddc450da3fe4.jpg";

    ImageView img1;
    ImageView img2;
    ImageView img3;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        img1 = (ImageView) findViewById(R.id.img1);
        img2 = (ImageView) findViewById(R.id.img2);
        img3 = (ImageView) findViewById(R.id.img3);

        ImageCache ic = new ImageCache(getBaseContext());
        ic.disPlayImage(img1, url1);
        ic.disPlayImage(img2, url2);
        ic.disPlayImage(img3, url3);

    }

}