Android LruCache & DiskLruCache cooperate working in ListView

小鱼儿 2023-10-17 16:13 28阅读 0赞

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<String, Bitmap> 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;
        }
    }