三级缓存来减少不必要的网络请求，节省流量。
- 内存缓存，优先加载，速度最快
- 本地缓存，次要加载，速度快
- 网络缓存，最后加载，速度慢
内存缓存实现1
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37public class MemoryCacheUtils {
private LruCache<String, Bitmap> mMemoryCache;
public MemoryCacheUtils() {
long maxMemory = Runtime.getRuntime().maxMemory() / 8;//得到手机最大允许内存的1/8,即超过指定内存,则开始回收
//需要传入允许的内存最大值,虚拟机默认内存16M,真机不一定相同
mMemoryCache = new LruCache<String, Bitmap>((int) maxMemory) {
//用于计算每个条目的大小
@Override
protected int sizeOf(String key, Bitmap value) {
return value.getByteCount();
}
};
}
/**
* 从内存中读图片
*
* @param url
*/
public Bitmap getBitmapFromMemory(String url) {
Bitmap bitmap = mMemoryCache.get(url);
return bitmap;
}
/**
* 往内存中写图片
*
* @param url
* @param bitmap
*/
public void setBitmapToMemory(String url, Bitmap bitmap) {
mMemoryCache.put(url, bitmap);
}
}
本地缓存实现1
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43public class LocalCacheUtils {
private static final String CACHE_PATH = Environment.getExternalStorageDirectory().getAbsolutePath() + "/WerbNews";
/**
* 从本地读取图片
* @param url
*/
public Bitmap getBitmapFromLocal(String url) {
String fileName = null;//把图片的url当做文件名,并进行MD5加密
try {
fileName = EncryptUtil.mapUrl(url);
File file = new File(CACHE_PATH, fileName);
Bitmap bitmap = BitmapFactory.decodeStream(new FileInputStream(file));
return bitmap;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* 从网络获取图片后,保存至本地缓存
* @param url
* @param bitmap
*/
public void setBitmapToLocal(String url, Bitmap bitmap) {
try {
String fileName = EncryptUtil.mapUrl(url);//把图片的url当做文件名,并进行MD5加密
File file = new File(CACHE_PATH, fileName);
//通过得到文件的父文件,判断父文件是否存在
File parentFile = file.getParentFile();
if (!parentFile.exists()) {
parentFile.mkdirs();
}
//把图片保存至本地
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, new FileOutputStream(file));
} catch (Exception e) {
e.printStackTrace();
}
}
}
网络缓存实现1
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99public class NetCacheUtils {
private LocalCacheUtils mLocalCacheUtils;
private MemoryCacheUtils mMemoryCacheUtils;
public NetCacheUtils(LocalCacheUtils localCacheUtils, MemoryCacheUtils memoryCacheUtils) {
mLocalCacheUtils = localCacheUtils;
mMemoryCacheUtils = memoryCacheUtils;
}
/**
* 从网络下载图片
* @param ivPic 显示图片的imageview
* @param url 下载图片的网络地址
*/
public void getBitmapFromNet(ImageView ivPic, String url) {
new BitmapTask().execute(ivPic, url);//启动AsyncTask
}
/**
* AsyncTask就是对handler和线程池的封装
* 第一个泛型:参数类型
* 第二个泛型:更新进度的泛型
* 第三个泛型:onPostExecute的返回结果
*/
class BitmapTask extends AsyncTask<Object, Void, Bitmap> {
private ImageView ivPic;
private String url;
/**
* 后台耗时操作,存在于子线程中
* @param params
* @return
*/
@Override
protected Bitmap doInBackground(Object[] params) {
ivPic = (ImageView) params[0];
url = (String) params[1];
return downLoadBitmap(url);
}
/**
* 更新进度,在主线程中
* @param values
*/
@Override
protected void onProgressUpdate(Void[] values) {
super.onProgressUpdate(values);
}
/**
* 耗时方法结束后执行该方法,主线程中
* @param result
*/
@Override
protected void onPostExecute(Bitmap result) {
if (result != null) {
ivPic.setImageBitmap(result);
System.out.println("从网络缓存图片啦.....");
//从网络获取图片后,保存至本地缓存
mLocalCacheUtils.setBitmapToLocal(url, result);
//保存至内存中
mMemoryCacheUtils.setBitmapToMemory(url, result);
}
}
}
/**
* 网络下载图片
* @param url
* @return
*/
private Bitmap downLoadBitmap(String url) {
HttpURLConnection conn = null;
try {
conn = (HttpURLConnection) new URL(url).openConnection();
conn.setConnectTimeout(5000);
conn.setReadTimeout(5000);
conn.setRequestMethod("GET");
int responseCode = conn.getResponseCode();
if (responseCode == 200) {
//图片压缩
BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize=2;//宽高压缩为原来的1/2
options.inPreferredConfig=Bitmap.Config.ARGB_4444;
Bitmap bitmap = BitmapFactory.decodeStream(conn.getInputStream(),null,options);
return bitmap;
}
} catch (IOException e) {
e.printStackTrace();
} finally {
conn.disconnect();
}
return null;
}
}
MD5加密1
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19public class EncryptUtil {
public EncryptUtil() {
}
public static String mapUrl(String url) {
StringBuilder builder = new StringBuilder();
try {
MessageDigest md5 = MessageDigest.getInstance("MD5");
byte[] bytes = md5.digest(url.getBytes());
for (byte b : bytes) {
builder.append(String.format("%02x", b));
}
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
return builder.toString();
}
}
图片加载工具类1
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36public class MyBitmapUtils {
private NetCacheUtils mNetCacheUtils;
private LocalCacheUtils mLocalCacheUtils;
private MemoryCacheUtils mMemoryCacheUtils;
public MyBitmapUtils() {
mMemoryCacheUtils = new MemoryCacheUtils();
mLocalCacheUtils = new LocalCacheUtils();
mNetCacheUtils = new NetCacheUtils(mLocalCacheUtils, mMemoryCacheUtils);
}
public void disPlay(ImageView ivPic, String url) {
ivPic.setImageResource(R.mipmap.ic_launcher);
Bitmap bitmap;
//内存缓存
bitmap = mMemoryCacheUtils.getBitmapFromMemory(url);
if (bitmap != null) {
ivPic.setImageBitmap(bitmap);
System.out.println("从内存获取图片啦.....");
return;
}
//本地缓存
bitmap = mLocalCacheUtils.getBitmapFromLocal(url);
if (bitmap != null) {
ivPic.setImageBitmap(bitmap);
System.out.println("从本地获取图片啦.....");
//从本地获取图片后,保存至内存中
mMemoryCacheUtils.setBitmapToMemory(url, bitmap);
return;
}
//网络缓存
mNetCacheUtils.getBitmapFromNet(ivPic, url);
}
}
