本文介绍LRU缓存的实现方法，并对比了一种简单轻量级的本地缓存框架asimple，以及更高级的disklrucache框架。详细展示了不同缓存框架的应用场景、初始化方式和图片缓存的实现。
1.lrucache的使用
初始化cache及设置大小：
private void init() {
//获取最大可用内存
int maxMemory = (int) Runtime.getRuntime().maxMemory();
//设置缓存的大小
int cacheSize = maxMemory / 8;
mCache=new LruCache<String, Bitmap>(cacheSize){
@Override
protected int sizeOf(String key, Bitmap value) {
return value.getByteCount();
}
};
}储存数据：
mCache.put(url,bitmap);提取数据：
mCache.get(list.get(position)就是这样这个lrucache没有储存到本地：
下面是整个activity，用了一个listview来展现其中用了rxjava和retrofit：
package com.cheerchip.lrucache.actvity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.LruCache;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.RelativeLayout;
import com.cheerchip.lrucache.Const;
import com.cheerchip.lrucache.HttpService;
import com.cheerchip.lrucache.HttpUtils;
import com.cheerchip.lrucache.R;
import com.jakewharton.disklrucache.DiskLruCache;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.List;
import okhttp3.ResponseBody;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import rx.Observable;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;
/**
* Created by noname on 2017/6/19.
*/
public class LruCacheActivity extends AppCompatActivity {
List<String> list=new ArrayList<>();
private BaseAdapter adapter;
private LruCache<String, Bitmap> mCache;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.lrulayout);
findViewById(R.id.bt13).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
click4();
}
});
init();
ListView listView= ((ListView) findViewById(R.id.listlru));
adapter = new BaseAdapter() {
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageview =new ImageView(LruCacheActivity.this);
RelativeLayout.LayoutParams params=new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
imageview.setLayoutParams(params);
if (mCache.get(list.get(position))!=null){
imageview.setImageBitmap(mCache.get(list.get(position)));
}else {
getimage(list.get(position), imageview);
}
return imageview;
}
};
listView.setAdapter(adapter);
}
private void init() {
//获取最大可用内存
int maxMemory = (int) Runtime.getRuntime().maxMemory();
//设置缓存的大小
int cacheSize = maxMemory / 8;
mCache=new LruCache<String, Bitmap>(cacheSize){
@Override
protected int sizeOf(String key, Bitmap value) {
return value.getByteCount();
}
};
}
//下载图片
public void getimage(final String url, final ImageView imageView){
Call<ResponseBody> call= HttpUtils.getInstance().getService().downloadPicFromNet(url);
call.enqueue(new Callback<ResponseBody>() {
@Override
public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
InputStream inputStream= response.body().byteStream();
final Bitmap bitmap= BitmapFactory.decodeStream(inputStream);
Observable.just(bitmap)
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe(new Subscriber<Bitmap>() {
@Override
public void onCompleted() {
}
@Override
public void onError(Throwable e) {
}
@Override
public void onNext(Bitmap bitmap) {
mCache.put(url,bitmap);
imageView.setImageBitmap(bitmap);
}
});
}
@Override
public void onFailure(Call<ResponseBody> call, Throwable t) {
}
});
}
public void click4() {
list.clear();
list.add(Const.url1);
list.add(Const.url2);
list.add(Const.url3);
list.add(Const.url4);
list.add(Const.url5);
list.add(Const.url6);
list.add(Const.url7);
list.add(Const.url8);
adapter.notifyDataSetChanged();
}
public void clearcache(){
//清空所有缓存
mCache.evictAll();
}
}
z这个框架比较简单轻量级的储存到了本地：
整个框架就是一个类在github有2000多的star：
/**
* Copyright (c) 2012-2013, Michael Yang 杨福海 (www.yangfuhai.com).
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.cheerchip.lrucache.Asimple;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.RandomAccessFile;
import java.io.Serializable;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import org.json.JSONArray;
import org.json.JSONObject;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.PixelFormat;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
/**
* @author Michael Yang（www.yangfuhai.com） update at 2013.08.07
*/
public class ACache {
public static final int TIME_HOUR = 60 * 60;
public static final int TIME_DAY = TIME_HOUR * 24;
private static final int MAX_SIZE = 1000 * 1000 * 50; // 50 mb
private static final int MAX_COUNT = Integer.MAX_VALUE; // 不限制存放数据的数量
private static Map<String, ACache> mInstanceMap = new HashMap<String, ACache>();
private ACacheManager mCache;
public static ACache get(Context ctx) {
return get(ctx, "ACache");
}
public static ACache get(Context ctx, String cacheName) {
File f = new File(ctx.getCacheDir(), cacheName);
return get(f, MAX_SIZE, MAX_COUNT);
}
public static ACache get(File cacheDir) {
return get(cacheDir, MAX_SIZE, MAX_COUNT);
}
public static ACache get(Context ctx, long max_zise, int max_count) {
File f = new File(ctx.getCacheDir(), "ACache");
return get(f, max_zise, max_count);
}
public static ACache get(File cacheDir, long max_zise, int max_count) {
ACache manager = mInstanceMap.get(cacheDir.getAbsoluteFile() + myPid());
if (manager == null) {
manager = new ACache(cacheDir, max_zise, max_count);
mInstanceMap.put(cacheDir.getAbsolutePath() + myPid(), manager);
}
return manager;
}
private static String myPid() {
return "_" + android.os.Process.myPid();
}
private ACache(File cacheDir, long max_size, int max_count) {
if (!cacheDir.exists() && !cacheDir.mkdirs()) {
throw new RuntimeException("can't make dirs in "
+ cacheDir.getAbsolutePath());
}
mCache = new ACacheManager(cacheDir, max_size, max_count);
}
// =======================================
// ============ String数据 读写 ==============
// =======================================
/**
* 保存 String数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的String数据
*/
public void put(String key, String value) {
File file = mCache.newFile(key);
BufferedWriter out = null;
try {
out = new BufferedWriter(new FileWriter(file), 1024);
out.write(value);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (out != null) {
try {
out.flush();
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
mCache.put(file);
}
}
/**
* 保存 String数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的String数据
* @param saveTime
* 保存的时间，单位：秒
*/
public void put(String key, String value, int saveTime) {
put(key, Utils.newStringWithDateInfo(saveTime, value));
}
/**
* 读取 String数据
*
* @param key
* @return String 数据
*/
public String getAsString(String key) {
File file = mCache.get(key);
if (!file.exists())
return null;
boolean removeFile = false;
BufferedReader in = null;
try {
in = new BufferedReader(new FileReader(file));
String readString = "";
String currentLine;
while ((currentLine = in.readLine()) != null) {
readString += currentLine;
}
if (!Utils.isDue(readString)) {
return Utils.clearDateInfo(readString);
} else {
removeFile = true;
return null;
}
} catch (IOException e) {
e.printStackTrace();
return null;
} finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (removeFile)
remove(key);
}
}
// =======================================
// ============= JSONObject 数据 读写 ==============
// =======================================
/**
* 保存 JSONObject数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的JSON数据
*/
public void put(String key, JSONObject value) {
put(key, value.toString());
}
/**
* 保存 JSONObject数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的JSONObject数据
* @param saveTime
* 保存的时间，单位：秒
*/
public void put(String key, JSONObject value, int saveTime) {
put(key, value.toString(), saveTime);
}
/**
* 读取JSONObject数据
*
* @param key
* @return JSONObject数据
*/
public JSONObject getAsJSONObject(String key) {
String JSONString = getAsString(key);
try {
JSONObject obj = new JSONObject(JSONString);
return obj;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
// =======================================
// ============ JSONArray 数据 读写 =============
// =======================================
/**
* 保存 JSONArray数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的JSONArray数据
*/
public void put(String key, JSONArray value) {
put(key, value.toString());
}
/**
* 保存 JSONArray数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的JSONArray数据
* @param saveTime
* 保存的时间，单位：秒
*/
public void put(String key, JSONArray value, int saveTime) {
put(key, value.toString(), saveTime);
}
/**
* 读取JSONArray数据
*
* @param key
* @return JSONArray数据
*/
public JSONArray getAsJSONArray(String key) {
String JSONString = getAsString(key);
try {
JSONArray obj = new JSONArray(JSONString);
return obj;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
// =======================================
// ============== byte 数据 读写 =============
// =======================================
/**
* 保存 byte数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的数据
*/
public void put(String key, byte[] value) {
File file = mCache.newFile(key);
FileOutputStream out = null;
try {
out = new FileOutputStream(file);
out.write(value);
} catch (Exception e) {
e.printStackTrace();
} finally {
if (out != null) {
try {
out.flush();
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
mCache.put(file);
}
}
/**
* 保存 byte数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的数据
* @param saveTime
* 保存的时间，单位：秒
*/
public void put(String key, byte[] value, int saveTime) {
put(key, Utils.newByteArrayWithDateInfo(saveTime, value));
}
/**
* 获取 byte 数据
*
* @param key
* @return byte 数据
*/
public byte[] getAsBinary(String key) {
RandomAccessFile RAFile = null;
boolean removeFile = false;
try {
File file = mCache.get(key);
if (!file.exists())
return null;
RAFile = new RandomAccessFile(file, "r");
byte[] byteArray = new byte[(int) RAFile.length()];
RAFile.read(byteArray);
if (!Utils.isDue(byteArray)) {
return Utils.clearDateInfo(byteArray);
} else {
removeFile = true;
return null;
}
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
if (RAFile != null) {
try {
RAFile.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (removeFile)
remove(key);
}
}
// =======================================
// ============= 序列化 数据 读写 ===============
// =======================================
/**
* 保存 Serializable数据 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的value
*/
public void put(String key, Serializable value) {
put(key, value, -1);
}
/**
* 保存 Serializable数据到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的value
* @param saveTime
* 保存的时间，单位：秒
*/
public void put(String key, Serializable value, int saveTime) {
ByteArrayOutputStream baos = null;
ObjectOutputStream oos = null;
try {
baos = new ByteArrayOutputStream();
oos = new ObjectOutputStream(baos);
oos.writeObject(value);
byte[] data = baos.toByteArray();
if (saveTime != -1) {
put(key, data, saveTime);
} else {
put(key, data);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
oos.close();
} catch (IOException e) {
}
}
}
/**
* 读取 Serializable数据
*
* @param key
* @return Serializable 数据
*/
public Object getAsObject(String key) {
byte[] data = getAsBinary(key);
if (data != null) {
ByteArrayInputStream bais = null;
ObjectInputStream ois = null;
try {
bais = new ByteArrayInputStream(data);
ois = new ObjectInputStream(bais);
Object reObject = ois.readObject();
return reObject;
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
try {
if (bais != null)
bais.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
if (ois != null)
ois.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
// =======================================
// ============== bitmap 数据 读写 =============
// =======================================
/**
* 保存 bitmap 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的bitmap数据
*/
public void put(String key, Bitmap value) {
put(key, Utils.Bitmap2Bytes(value));
}
/**
* 保存 bitmap 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的 bitmap 数据
* @param saveTime
* 保存的时间，单位：秒
*/
public void put(String key, Bitmap value, int saveTime) {
put(key, Utils.Bitmap2Bytes(value), saveTime);
}
/**
* 读取 bitmap 数据
*
* @param key
* @return bitmap 数据
*/
public Bitmap getAsBitmap(String key) {
if (getAsBinary(key) == null) {
return null;
}
return Utils.Bytes2Bimap(getAsBinary(key));
}
// =======================================
// ============= drawable 数据 读写 =============
// =======================================
/**
* 保存 drawable 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的drawable数据
*/
public void put(String key, Drawable value) {
put(key, Utils.drawable2Bitmap(value));
}
/**
* 保存 drawable 到 缓存中
*
* @param key
* 保存的key
* @param value
* 保存的 drawable 数据
* @param saveTime
* 保存的时间，单位：秒
*/
public void put(String key, Drawable value, int saveTime) {
put(key, Utils.drawable2Bitmap(value), saveTime);
}
/**
* 读取 Drawable 数据
*
* @param key
* @return Drawable 数据
*/
public Drawable getAsDrawable(String key) {
if (getAsBinary(key) == null) {
return null;
}
return Utils.bitmap2Drawable(Utils.Bytes2Bimap(getAsBinary(key)));
}
/**
* 获取缓存文件
*
* @param key
* @return value 缓存的文件
*/
public File file(String key) {
File f = mCache.newFile(key);
if (f.exists())
return f;
return null;
}
/**
* 移除某个key
*
* @param key
* @return 是否移除成功
*/
public boolean remove(String key) {
return mCache.remove(key);
}
/**
* 清除所有数据
*/
public void clear() {
mCache.clear();
}
/**
* @title 缓存管理器
* @author 杨福海（michael） www.yangfuhai.com
* @version 1.0
*/
public class ACacheManager {
private final AtomicLong cacheSize;
private final AtomicInteger cacheCount;
private final long sizeLimit;
private final int countLimit;
private final Map<File, Long> lastUsageDates = Collections
.synchronizedMap(new HashMap<File, Long>());
protected File cacheDir;
private ACacheManager(File cacheDir, long sizeLimit, int countLimit) {
this.cacheDir = cacheDir;
this.sizeLimit = sizeLimit;
this.countLimit = countLimit;
cacheSize = new AtomicLong();
cacheCount = new AtomicInteger();
calculateCacheSizeAndCacheCount();
}
/**
* 计算 cacheSize和cacheCount
*/
private void calculateCacheSizeAndCacheCount() {
new Thread(new Runnable() {
@Override
public void run() {
int size = 0;
int count = 0;
File[] cachedFiles = cacheDir.listFiles();
if (cachedFiles != null) {
for (File cachedFile : cachedFiles) {
size += calculateSize(cachedFile);
count += 1;
lastUsageDates.put(cachedFile,
cachedFile.lastModified());
}
cacheSize.set(size);
cacheCount.set(count);
}
}
}).start();
}
private void put(File file) {
int curCacheCount = cacheCount.get();
while (curCacheCount + 1 > countLimit) {
long freedSize = removeNext();
cacheSize.addAndGet(-freedSize);
curCacheCount = cacheCount.addAndGet(-1);
}
cacheCount.addAndGet(1);
long valueSize = calculateSize(file);
long curCacheSize = cacheSize.get();
while (curCacheSize + valueSize > sizeLimit) {
long freedSize = removeNext();
curCacheSize = cacheSize.addAndGet(-freedSize);
}
cacheSize.addAndGet(valueSize);
Long currentTime = System.currentTimeMillis();
file.setLastModified(currentTime);
lastUsageDates.put(file, currentTime);
}
private File get(String key) {
File file = newFile(key);
Long currentTime = System.currentTimeMillis();
file.setLastModified(currentTime);
lastUsageDates.put(file, currentTime);
return file;
}
private File newFile(String key) {
return new File(cacheDir, key.hashCode() + "");
}
private boolean remove(String key) {
File image = get(key);
return image.delete();
}
private void clear() {
lastUsageDates.clear();
cacheSize.set(0);
File[] files = cacheDir.listFiles();
if (files != null) {
for (File f : files) {
f.delete();
}
}
}
/**
* 移除旧的文件
*
* @return
*/
private long removeNext() {
if (lastUsageDates.isEmpty()) {
return 0;
}
Long oldestUsage = null;
File mostLongUsedFile = null;
Set<Entry<File, Long>> entries = lastUsageDates.entrySet();
synchronized (lastUsageDates) {
for (Entry<File, Long> entry : entries) {
if (mostLongUsedFile == null) {
mostLongUsedFile = entry.getKey();
oldestUsage = entry.getValue();
} else {
Long lastValueUsage = entry.getValue();
if (lastValueUsage < oldestUsage) {
oldestUsage = lastValueUsage;
mostLongUsedFile = entry.getKey();
}
}
}
}
long fileSize = calculateSize(mostLongUsedFile);
if (mostLongUsedFile.delete()) {
lastUsageDates.remove(mostLongUsedFile);
}
return fileSize;
}
private long calculateSize(File file) {
return file.length();
}
}
/**
* @title 时间计算工具类
* @author 杨福海（michael） www.yangfuhai.com
* @version 1.0
*/
private static class Utils {
/**
* 判断缓存的String数据是否到期
*
* @param str
* @return true：到期了 false：还没有到期
*/
private static boolean isDue(String str) {
return isDue(str.getBytes());
}
/**
* 判断缓存的byte数据是否到期
*
* @param data
* @return true：到期了 false：还没有到期
*/
private static boolean isDue(byte[] data) {
String[] strs = getDateInfoFromDate(data);
if (strs != null && strs.length == 2) {
String saveTimeStr = strs[0];
while (saveTimeStr.startsWith("0")) {
saveTimeStr = saveTimeStr
.substring(1, saveTimeStr.length());
}
long saveTime = Long.valueOf(saveTimeStr);
long deleteAfter = Long.valueOf(strs[1]);
if (System.currentTimeMillis() > saveTime + deleteAfter * 1000) {
return true;
}
}
return false;
}
private static String newStringWithDateInfo(int second, String strInfo) {
return createDateInfo(second) + strInfo;
}
private static byte[] newByteArrayWithDateInfo(int second, byte[] data2) {
byte[] data1 = createDateInfo(second).getBytes();
byte[] retdata = new byte[data1.length + data2.length];
System.arraycopy(data1, 0, retdata, 0, data1.length);
System.arraycopy(data2, 0, retdata, data1.length, data2.length);
return retdata;
}
private static String clearDateInfo(String strInfo) {
if (strInfo != null && hasDateInfo(strInfo.getBytes())) {
strInfo = strInfo.substring(strInfo.indexOf(mSeparator) + 1,
strInfo.length());
}
return strInfo;
}
private static byte[] clearDateInfo(byte[] data) {
if (hasDateInfo(data)) {
return copyOfRange(data, indexOf(data, mSeparator) + 1,
data.length);
}
return data;
}
private static boolean hasDateInfo(byte[] data) {
return data != null && data.length > 15 && data[13] == '-'
&& indexOf(data, mSeparator) > 14;
}
private static String[] getDateInfoFromDate(byte[] data) {
if (hasDateInfo(data)) {
String saveDate = new String(copyOfRange(data, 0, 13));
String deleteAfter = new String(copyOfRange(data, 14,
indexOf(data, mSeparator)));
return new String[] { saveDate, deleteAfter };
}
return null;
}
private static int indexOf(byte[] data, char c) {
for (int i = 0; i < data.length; i++) {
if (data[i] == c) {
return i;
}
}
return -1;
}
private static byte[] copyOfRange(byte[] original, int from, int to) {
int newLength = to - from;
if (newLength < 0)
throw new IllegalArgumentException(from + " > " + to);
byte[] copy = new byte[newLength];
System.arraycopy(original, from, copy, 0,
Math.min(original.length - from, newLength));
return copy;
}
private static final char mSeparator = ' ';
private static String createDateInfo(int second) {
String currentTime = System.currentTimeMillis() + "";
while (currentTime.length() < 13) {
currentTime = "0" + currentTime;
}
return currentTime + "-" + second + mSeparator;
}
/*
* Bitmap → byte[]
*/
private static byte[] Bitmap2Bytes(Bitmap bm) {
if (bm == null) {
return null;
}
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
return baos.toByteArray();
}
/*
* byte[] → Bitmap
*/
private static Bitmap Bytes2Bimap(byte[] b) {
if (b.length == 0) {
return null;
}
return BitmapFactory.decodeByteArray(b, 0, b.length);
}
/*
* Drawable → Bitmap
*/
private static Bitmap drawable2Bitmap(Drawable drawable) {
if (drawable == null) {
return null;
}
// 取 drawable 的长宽
int w = drawable.getIntrinsicWidth();
int h = drawable.getIntrinsicHeight();
// 取 drawable 的颜色格式
Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
: Bitmap.Config.RGB_565;
// 建立对应 bitmap
Bitmap bitmap = Bitmap.createBitmap(w, h, config);
// 建立对应 bitmap 的画布
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, w, h);
// 把 drawable 内容画到画布中
drawable.draw(canvas);
return bitmap;
}
/*
* Bitmap → Drawable
*/
@SuppressWarnings("deprecation")
private static Drawable bitmap2Drawable(Bitmap bm) {
if (bm == null) {
return null;
}
return new BitmapDrawable(bm);
}
}
}
设置储存时间，初始化acache和储存提取：
ACache mCache = ACache.get(this);
* mCache.put("test_key1", "test value");
* mCache.put("test_key2", "test value", 10);//保存10秒，如果超过10秒去获取这个key，将为null
* mCache.put("test_key3", "test value", 2 * ACache.TIME_DAY);//保存两天，如果超过两天去获取这个key，将为null
* ACache mCache = ACache.get(this);
* String value = mCache.getAsString("test_key1");整个类的实用如下：
package com.cheerchip.lrucache.actvity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.LruCache;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.RelativeLayout;
import com.cheerchip.lrucache.Asimple.ACache;
import com.cheerchip.lrucache.Const;
import com.cheerchip.lrucache.HttpUtils;
import com.cheerchip.lrucache.R;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import okhttp3.ResponseBody;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import rx.Observable;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;
/**
* Created by noname on 2017/6/20.
* ACache mCache = ACache.get(this);
* mCache.put("test_key1", "test value");
* mCache.put("test_key2", "test value", 10);//保存10秒，如果超过10秒去获取这个key，将为null
* mCache.put("test_key3", "test value", 2 * ACache.TIME_DAY);//保存两天，如果超过两天去获取这个key，将为null
* ACache mCache = ACache.get(this);
* String value = mCache.getAsString("test_key1");
* https://github.com/yangfuhai/ASimpleCache
*/
public class AsimpleActivity extends AppCompatActivity{
List<String> list=new ArrayList<>();
private BaseAdapter adapter;
private ACache mCache;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.lrulayout);
findViewById(R.id.bt13).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
click4();
}
});
init();
ListView listView= ((ListView) findViewById(R.id.listlru));
adapter = new BaseAdapter() {
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageview =new ImageView(AsimpleActivity.this);
RelativeLayout.LayoutParams params=new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
imageview.setLayoutParams(params);
if (mCache.getAsBitmap(list.get(position))!=null){
imageview.setImageBitmap(mCache.getAsBitmap(list.get(position)));
}else {
getimage(list.get(position), imageview);
}
return imageview;
}
};
listView.setAdapter(adapter);
}
private void init() {
//获取最大可用内存
int maxMemory = (int) Runtime.getRuntime().maxMemory();
//设置缓存的大小
int cacheSize = maxMemory / 8;
mCache=ACache.get(this);
}
//下载图片
public void getimage(final String url, final ImageView imageView){
Call<ResponseBody> call= HttpUtils.getInstance().getService().downloadPicFromNet(url);
call.enqueue(new Callback<ResponseBody>() {
@Override
public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
InputStream inputStream= response.body().byteStream();
final Bitmap bitmap= BitmapFactory.decodeStream(inputStream);
Observable.just(bitmap)
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe(new Subscriber<Bitmap>() {
@Override
public void onCompleted() {
}
@Override
public void onError(Throwable e) {
}
@Override
public void onNext(Bitmap bitmap) {
mCache.put(url,bitmap,2*ACache.TIME_DAY);
imageView.setImageBitmap(bitmap);
}
});
}
@Override
public void onFailure(Call<ResponseBody> call, Throwable t) {
}
});
}
public void click4() {
list.clear();
list.add(Const.url1);
list.add(Const.url2);
list.add(Const.url3);
list.add(Const.url4);
list.add(Const.url5);
list.add(Const.url6);
list.add(Const.url7);
list.add(Const.url8);
adapter.notifyDataSetChanged();
}
public void clearcache(){
//清空所有缓存
mCache.clear();
}
}
3.第三个是比较高级的okhttp，retrofit的作者写的在这几个框架中也有使用的储存框架
储存图片的方法使用了url的md5当成key储存value则是字节流
：
//储存图片
public boolean addBitmapToDiskLruCache(String imageUrl,Bitmap bitmap) {
boolean result = false;
String key = hashKeyForDisk(imageUrl); // 通过md5加密了这个URL，生成一个key
try {
DiskLruCache.Editor editor = mDiskLruCache.edit(key);// 产生一个editor对象
if (editor != null) {
// 创建一个新的输出流 ，创建DiskLruCache时设置一个节点只有一个数据，所以这里的index直接设为0即可
OutputStream outputStream = editor.newOutputStream(0);
// 通过地址获取图片数据写入到输出流
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
InputStream isBm = new ByteArrayInputStream(baos.toByteArray());
if (writebp(isBm,outputStream)) {
// 写入成功，提交
editor.commit();
result = true;
} else {
// 写入失败，中止
editor.abort();
result = false;
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
2.提取图片也和上面几个框架类似：
/**
* 从缓存中获取Bitmap对象
*/
public Bitmap getCacheBitmap(String imageUrl) {
String key = hashKeyForDisk(imageUrl);// 把Url转换成KEY
try {
DiskLruCache.Snapshot snapShot = mDiskLruCache.get(key);// 通过key获取Snapshot对象
if (snapShot != null) {
InputStream is = snapShot.getInputStream(0);// 通过Snapshot对象获取缓存文件的输入流
Bitmap bitmap = BitmapFactory.decodeStream(is);// 把输入流转换成Bitmap对象
return bitmap;
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}3.初始化disklrucache：
public void initDiskLruCache(Context context) {
try {
File cacheDir = new File("/sdcard/image");
if (!cacheDir.exists()) {
cacheDir.mkdirs();
}
mDiskLruCache = DiskLruCache.open(cacheDir, getversion(context), VALUES_COUNT, DISK_CACHE_SIZE);
Log.e("getCacheBitmap: ",(mDiskLruCache==null)+"" );
} catch (IOException e) {
e.printStackTrace();
}
}下面是整个cache的工具类：
package com.cheerchip.lrucache;
import android.content.Context;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import com.jakewharton.disklrucache.DiskLruCache;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
/**
* Created by noname on 2017/6/20.
*/
public class DiskLruCacheUtils {
private DiskLruCache mDiskLruCache;
private static final int DISK_CACHE_SIZE = 1024 * 1024 * 50; // 磁盘缓存的大小为50M
private static final String DISK_CACHE_SUBDIR = "bitmap"; // 设置缓存的文件名bitmap
private static final int APP_VERSION = 1;
private static final int VALUES_COUNT = 1;
private static final int CPU_COUNT = Runtime.getRuntime()
.availableProcessors();
private static final int CORE_POOL_SIZE = CPU_COUNT + 1;// 核心线程数
private ExecutorService pool;// 线程池
private Future future;
private static final String TAG = "DiskLruCacheUtils";
public static final int MESSAGE_POST_RESULT = 1;
public void initDiskLruCache(Context context) {
try {
File cacheDir = new File("/sdcard/image");
if (!cacheDir.exists()) {
cacheDir.mkdirs();
}
mDiskLruCache = DiskLruCache.open(cacheDir, getversion(context), VALUES_COUNT, DISK_CACHE_SIZE);
Log.e("getCacheBitmap: ",(mDiskLruCache==null)+"" );
} catch (IOException e) {
e.printStackTrace();
}
}
Context context;
public DiskLruCacheUtils() {
}
public DiskLruCacheUtils(Context context) {
this.context = context;
initDiskLruCache(context);
}
//获取当前版本号
private int getversion(Context context){
try {
return context.getPackageManager().getPackageInfo(
context.getPackageName(), 0).versionCode;
} catch (PackageManager.NameNotFoundException e) {
e.printStackTrace();
return 1;
}
}
/**
* 从缓存中获取Bitmap对象
*/
public Bitmap getCacheBitmap(String imageUrl) {
String key = hashKeyForDisk(imageUrl);// 把Url转换成KEY
try {
DiskLruCache.Snapshot snapShot = mDiskLruCache.get(key);// 通过key获取Snapshot对象
if (snapShot != null) {
InputStream is = snapShot.getInputStream(0);// 通过Snapshot对象获取缓存文件的输入流
Bitmap bitmap = BitmapFactory.decodeStream(is);// 把输入流转换成Bitmap对象
return bitmap;
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
//储存图片
public boolean addBitmapToDiskLruCache(String imageUrl,Bitmap bitmap) {
boolean result = false;
String key = hashKeyForDisk(imageUrl); // 通过md5加密了这个URL，生成一个key
try {
DiskLruCache.Editor editor = mDiskLruCache.edit(key);// 产生一个editor对象
if (editor != null) {
// 创建一个新的输出流 ，创建DiskLruCache时设置一个节点只有一个数据，所以这里的index直接设为0即可
OutputStream outputStream = editor.newOutputStream(0);
// 通过地址获取图片数据写入到输出流
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
InputStream isBm = new ByteArrayInputStream(baos.toByteArray());
if (writebp(isBm,outputStream)) {
// 写入成功，提交
editor.commit();
result = true;
} else {
// 写入失败，中止
editor.abort();
result = false;
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
//读写
private static boolean writebp(InputStream inputStream,OutputStream outputStream){
int len;
byte []bytes=new byte[1024];
try {
while ((len=inputStream.read(bytes))!=-1){
outputStream.write(bytes);
outputStream.flush();
}
return true;
} catch (IOException e) {
e.printStackTrace();
return false;
}
}
//将url转成MD5
public static String hashKeyForDisk(String key) {
String cacheKey;
try {
final MessageDigest mDigest = MessageDigest.getInstance("MD5");
mDigest.update(key.getBytes());
cacheKey = bytesToHexString(mDigest.digest());
} catch (NoSuchAlgorithmException e) {
cacheKey = String.valueOf(key.hashCode());
}
return cacheKey;
}
//将url转成MD5
private static String bytesToHexString(byte[] bytes) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < bytes.length; i++) {
String hex = Integer.toHexString(0xFF & bytes[i]);
if (hex.length() == 1) {
sb.append('0');
}
sb.append(hex);
}
return sb.toString();
}
}
package com.cheerchip.lrucache.actvity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.LruCache;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.RelativeLayout;
import com.cheerchip.lrucache.Const;
import com.cheerchip.lrucache.DiskLruCacheUtils;
import com.cheerchip.lrucache.HttpUtils;
import com.cheerchip.lrucache.R;
import com.jakewharton.disklrucache.DiskLruCache;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import okhttp3.ResponseBody;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import rx.Observable;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.functions.Func1;
import rx.schedulers.Schedulers;
/**
* Created by noname on 2017/6/20.
* https://github.com/JakeWharton/DiskLruCache/
*/
public class DisCacheActivity extends AppCompatActivity {
// DiskLruCache diskLruCache=DiskLruCache.create()
// DiskLruCache diskLruCache=DiskLruCache.open()
List<String> list=new ArrayList<>();
private BaseAdapter adapter;
private DiskLruCacheUtils diskLruCacheUtils;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.lrulayout);
init();
ListView listView= ((ListView) findViewById(R.id.listlru));
adapter = new BaseAdapter() {
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageview =new ImageView(DisCacheActivity.this);
RelativeLayout.LayoutParams params=new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
imageview.setLayoutParams(params);
Bitmap bitmap1=diskLruCacheUtils.getCacheBitmap(list.get(position));
if (bitmap1!=null){
imageview.setImageBitmap(bitmap1);
}else {
getimage(list.get(position), imageview);
}
return imageview;
}
};
listView.setAdapter(adapter);
}
private void init() {
findViewById(R.id.bt13).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
click4();
}
});
diskLruCacheUtils=new DiskLruCacheUtils(this);
}
//下载图片
public void getimage(final String url, final ImageView imageView){
Call<ResponseBody> call= HttpUtils.getInstance().getService().downloadPicFromNet(url);
call.enqueue(new Callback<ResponseBody>() {
@Override
public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
InputStream inputStream= response.body().byteStream();
final Bitmap bitmap= BitmapFactory.decodeStream(inputStream);
Observable.just(bitmap)
.filter(new Func1<Bitmap, Boolean>() {
@Override
public Boolean call(Bitmap bitmap) {
//子线程储存
diskLruCacheUtils.addBitmapToDiskLruCache(url,bitmap);
return true;
}
})
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe(new Subscriber<Bitmap>() {
@Override
public void onCompleted() {
}
@Override
public void onError(Throwable e) {
}
@Override
public void onNext(Bitmap bitmap) {
// diskLruCacheUtils.addBitmapToDiskLruCache(url,bitmap);
//主线程设置图片
imageView.setImageBitmap(bitmap);
}
});
}
@Override
public void onFailure(Call<ResponseBody> call, Throwable t) {
}
});
}
public void click4() {
list.clear();
list.add(Const.url1);
list.add(Const.url2);
list.add(Const.url3);
list.add(Const.url4);
list.add(Const.url5);
list.add(Const.url6);
list.add(Const.url7);
list.add(Const.url8);
adapter.notifyDataSetChanged();
}
}
就是这样了。
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