三级缓存练习--写个图片加载框架

使用DiskLruCache需要用到几个文件。

https://github.com/google/iosched/tree/master/third_party/disklrucache/src/main/java/com/jakewharton/disklrucache

public class ImageLoader {
    private static final String TAG = "ImageLoader";
    private static ImageLoader              instance;
    private        Handler                  mHandler;
    private        LruCache<String, Bitmap> mLruCache;
    //决定内存缓存的空间大小
    private int  maxMemSize  = 4 * 1024 * 1024;//8388608 byte
    //    private int maxMemSize = 8;//8 M
    public  long maxDiskSize = 40 * 1024 * 1024;//20m
    private DiskLruCache mDiskLruCache;
    private Context      mContext;

    private ImageLoader(Context context) {
        mContext = context;
        mHandler = new Handler();
        mLruCache = new LruCache<String, Bitmap>(maxMemSize) {
            //Returns the size of the entry for key and value in user-defined units
            //1.返回大小
            //2.根据用户定义的单位
            @Override
            protected int sizeOf(String key, Bitmap value) {
//                return super.sizeOf(key, value);//默认情况,一个图片只占一个byte
                //返回图片占的字节总数
                return value.getRowBytes() * value.getHeight();
            }
        };
        try {
            mDiskLruCache = DiskLruCache.open(getDirectory(), getAppversion(), 1, maxDiskSize);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 得到磁盘缓存的文件夹,优先放到外置sdcard
     *
     * @return
     */
    public File getDirectory() {
        File dir;
        String externalStorageState = Environment.getExternalStorageState();
        if (externalStorageState.equals(Environment.MEDIA_MOUNTED)) {//有sdcard
            dir = new File(Environment.getExternalStorageDirectory(), "/Android/data/" + mContext.getPackageName() + "/icon");
            if (!dir.exists()) {
                //创建文件夹
                dir.mkdirs();
            }
            return dir;
        } else {
            dir = mContext.getCacheDir();//data/data/包目录/caches
            return dir;
        }
    }

    public int getAppversion() {
        try {
            PackageInfo packageInfo = mContext.getPackageManager().getPackageInfo(mContext.getPackageName(), 0);
            return packageInfo.versionCode;
        } catch (PackageManager.NameNotFoundException e) {
            e.printStackTrace();
        }
        return 0;
    }


    public static ImageLoader getInstance(Context context) {
        if (instance == null) {
            instance = new ImageLoader(context);
        }
        return instance;
    }

    public void display(String url, final ImageView iv) {
        //清空身上已有的图片
        iv.setImageResource(R.drawable.news_pic_default);
        iv.setTag(url);

        String key = MD5Util.md5(url);

        //从内存,返回
        Bitmap bitmap = mLruCache.get(key);
        if (bitmap != null) {
            Log.d(TAG, "display 从内存里面加载图片");
            iv.setImageBitmap(bitmap);
            return;
        }
        //从磁盘,返回,存内存
        bitmap = loadImgFromDisk(key);
        if (bitmap != null) {
            //设置图片
            iv.setImageBitmap(bitmap);
            Log.d(TAG, "display 从磁盘加载图片");
            return;
        }

        //从网络,返回,存内存,存磁盘
        new Thread(new LoadImgTask(url, iv)).start();
    }

    /**
     * 从磁盘加载图片
     *
     * @param key
     * @return
     */
    private Bitmap loadImgFromDisk(String key) {
        try {
            DiskLruCache.Snapshot snapshot = mDiskLruCache.get(key);
            if (snapshot != null) {
                InputStream inputStream = snapshot.getInputStream(0);
                //inputStream-->Bitmap
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                if (bitmap != null) {
                    return bitmap;
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    class LoadImgTask implements Runnable {
        private String    url;
        private ImageView iv;

        public LoadImgTask(String url, ImageView iv) {
            this.url = url;
            this.iv = iv;
        }

        @Override
        public void run() {
            //使用okHttp发起请求
            try {
                OkHttpClient okHttpClient = new OkHttpClient();
                Request request = new Request.Builder().url(url).build();
                Response response = okHttpClient.newCall(request).execute();
                if (response.isSuccessful()) {
                    ResponseBody responseBody = response.body();
                    InputStream inputStream = responseBody.byteStream();
                    //inputStream-->bitmap
                    BitmapFactory.Options options = new BitmapFactory.Options();
                    options.inPreferredConfig = Bitmap.Config.ARGB_4444;
                    final Bitmap bitmap = BitmapFactory.decodeStream(inputStream, null, options);

                    //保存图片到内存中
                    save2Mem(url, bitmap);

                    //保存图片到磁盘中
                    save2Disk(url, bitmap);

                    mHandler.post(new Runnable() {
                        @Override
                        public void run() {
                            String curTag = (String) iv.getTag();
                            if (curTag.equals(url)) {
                                //设置
                                iv.setImageBitmap(bitmap);
                            }
                        }
                    });
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
            }
        }
    }

    /**
     * 保存图片到磁盘中
     *
     * @param url
     * @param bitmap
     */
    private void save2Disk(String url, Bitmap bitmap) {
        try {
            String key = MD5Util.md5(url);
            DiskLruCache.Editor editor = mDiskLruCache.edit(key);
            if (editor != null) {
                OutputStream outputStream = editor.newOutputStream(0);

                //把bitmap保存到输出流里面
                boolean compress = bitmap.compress(Bitmap.CompressFormat.JPEG, 100, outputStream);

                if (compress) {
                    editor.commit();
                    Log.d(TAG, "save2Disk 保存图片到磁盘中");
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 保存图片到内存中
     *
     * @param url
     * @param bitmap
     */
    private void save2Mem(String url, Bitmap bitmap) {
        if (TextUtils.isEmpty(url)) {
            return;
        }
        Log.d(TAG, "save2Mem 保存图片到内存中");
        String key = MD5Util.md5(url);
        if (mLruCache != null) {
            if (bitmap != null) {
                mLruCache.put(key, bitmap);
            }
        }
    }
}