Android(安卓)LruCache & DiskLruCache cooperate working in ListView

package zhangphil.cache;import android.app.ListActivity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.support.annotation.NonNull;import android.support.annotation.Nullable;import android.os.Bundle;import android.util.Log;import android.util.LruCache;import android.view.View;import android.view.ViewGroup;import android.widget.ArrayAdapter;import android.widget.ImageView;import java.io.ByteArrayOutputStream;import java.io.InputStream;import java.io.OutputStream;import java.security.MessageDigest;public class MainActivity extends ListActivity {    private LruCache mLruCache;    private DiskLruCache mDiskLruCache;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        int CACHE_SIZE = 8 * 1024 * 1024;        mLruCache = new LruCache(CACHE_SIZE);        try {            mDiskLruCache = DiskLruCache.open(this.getCacheDir(), 1, 1, CACHE_SIZE * 10);        } catch (Exception e) {            e.printStackTrace();        }        ArrayAdapter mAdapter = new ArrayAdapter(this, 0) {            @NonNull            @Override            public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {                ImageView image = new ImageView(getContext());                load(R.mipmap.ic_launcher, image);                return image;            }            @Override            public int getCount() {                return 20;            }        };        setListAdapter(mAdapter);    }    private void load(int id, ImageView image) {        String key = null;        if (id == R.mipmap.ic_launcher) {            key = getMD5("R.mipmap.ic_launcher");        }        //首先查找LruCache中的缓存        Bitmap bmp = mLruCache.get(key);        if (bmp == null) {            Log.d("LruCache缓存", "没有，继续深入到DiskLruCache读取。");            bmp = readFromDiskLruCache(key);            if (bmp == null) {                Log.d("LruCache与DiskLruCache", "没有缓存，开始创建新数据资源并缓存之。");                bmp = BitmapFactory.decodeResource(getResources(), id);                //初次创建新资源，更新到DiskLruCache                writeToDiskLruCache(key, bmp);            } else {                image.setImageBitmap(bmp);            }            //更新到LruCache缓存中，以待下一次使用。            mLruCache.put(key, bmp);            Log.d("LruCache缓存", "写入完成。");        } else {            //命中缓存            Log.d("LruCache缓存", "已有，复用。");            image.setImageBitmap(bmp);        }    }    private void writeToDiskLruCache(String key, Bitmap bmp) {        try {            DiskLruCache.Editor editor = mDiskLruCache.edit(key);            //把Bitmap转化为byte数组存储            ByteArrayOutputStream baos = new ByteArrayOutputStream();            bmp.compress(Bitmap.CompressFormat.PNG, 100, baos);            byte[] bytes = baos.toByteArray();            //再次把Bitmap数组写进为DiskLruCache准备的输出流。            OutputStream os = editor.newOutputStream(0);            os.write(bytes);            os.flush();            //正式写入DiskLruCache            editor.commit();            Log.d("DiskLruCache缓存", "写入缓存资源完毕。");        } catch (Exception e) {            e.printStackTrace();        }    }    private Bitmap readFromDiskLruCache(String key) {        DiskLruCache.Snapshot snapShot = null;        try {            snapShot = mDiskLruCache.get(key);        } catch (Exception e) {            e.printStackTrace();        }        Bitmap bmp = null;        if (snapShot != null) {            Log.d("DiskLruCache缓存", "发现资源，复用。");            InputStream is = snapShot.getInputStream(0);            bmp = BitmapFactory.decodeStream(is);        } else {            Log.d("DiskLruCache缓存", "没有发现缓存资源。");        }        return bmp;    }    private String getMD5(String msg) {        MessageDigest md = null;        try {            md = MessageDigest.getInstance("MD5");        } catch (Exception e) {            e.printStackTrace();        }        md.reset();        md.update(msg.getBytes());        byte[] bytes = md.digest();        String result = "";        for (byte b : bytes) {            result += String.format("%02x", b);        }        return result;    }}
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