关于Volley图片的三级缓存的基本使用

package com.example.volleycache;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import android.util.Log;
import android.util.LruCache;

import com.android.volley.toolbox.ImageLoader.ImageCache;

/*
* Volley中图片的本地缓存和内存缓存的使用；
*/
public class LruImageCache implements ImageCache {
//内存缓存
LruCache<String, Bitmap> lrucache;
//本地缓存
DiskLruCache disklrucache;
//本地缓存文件名
String DISK_CACHE_DIR = "volley_image";
//本地缓存大小
final long DISK_MAX_SIZE = 20 * 1024 * 1024;

private static LruImageCache lruImageCache = null;

public static LruImageCache getLruImageCache(Context context) {
if (lruImageCache == null) {
synchronized (Object.class) {
if (lruImageCache == null) {
lruImageCache = new LruImageCache(context);
}
}
}

return lruImageCache;
}

private LruImageCache(Context context) {
// TODO Auto-generated constructor stub
// 获取应用内存；
final int maxMemory = (int) Runtime.getRuntime().maxMemory();

final int cacheSize = maxMemory / 8;
// 初始化LruCache,设置缓存大小cacheSize；
this.lrucache = new LruCache<String, Bitmap>(cacheSize) {
@Override
protected int sizeOf(String key, Bitmap value) {
// TODO Auto-generated method stub
return value.getRowBytes() * value.getHeight();
}
};

/*
* 本地缓存
*/
final String disLruCachePath = context.getCacheDir().getPath();
//缓存路径
File disLruCachedir = new File(disLruCachePath + File.separator
+ DISK_CACHE_DIR);
if (!disLruCachedir.exists()) {
disLruCachedir.mkdirs();
}
try {
// 初始化DiskLruCache，设置最缓存大小DISK_MAX_SIZE；
/*参数一：路径
* 参数二：应用程序版本号
* 参数三：缓存文件数量
* 参数四：缓存大小
*/
disklrucache = DiskLruCache.open(disLruCachedir, 1, 1,
DISK_MAX_SIZE);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

@Override
public Bitmap getBitmap(String url) {
// TODO Auto-generated method stub
String key = MD5Utils.hashKeyForDisk(url);
// 先从内存中找
Bitmap bitmap = lrucache.get(url);
if (bitmap == null) {
//本地
bitmap = getBitmap_DiskLruCache(key);
// 放入内存
if (bitmap != null) {
lrucache.put(url, bitmap);
}
}
return bitmap;
}

@Override
public void putBitmap(String url, Bitmap bitmap) {
// TODO Auto-generated method stub
lrucache.put(url, bitmap);
String key = MD5Utils.hashKeyForDisk(url);
putBitmap_DiskLruCache(key, bitmap);
}

// 写入本地
private void putBitmap_DiskLruCache(String key, Bitmap bitmap) {
// TODO Auto-generated method stub
DiskLruCache.Editor editor = null;
OutputStream outputStream = null;
try {
editor = disklrucache.edit(key);
if (editor != null) {
outputStream = editor.newOutputStream(0);
boolean compress = bitmap.compress(Bitmap.CompressFormat.JPEG,
100, outputStream);
if (compress) {
disklrucache.flush();
editor.commit();
} else {
editor.abort();
}

}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (editor != null) {
editor.abort();
}
if (outputStream != null) {
outputStream.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}

}

// 从本地读取
private Bitmap getBitmap_DiskLruCache(String key) {
// TODO Auto-generated method stub
DiskLruCache.Snapshot snapshot = null;
Bitmap bitmap = null;
InputStream inputStream = null;
try {
snapshot = disklrucache.get(key);
if (snapshot != null) {
inputStream = snapshot.getInputStream(0);
if (inputStream != null) {
bitmap = BitmapFactory.decodeStream(inputStream);
}
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (snapshot != null) {
snapshot.close();
}
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return bitmap;
}

}