最近项目要求解决缓存方案，无意中发现Android早已经在4.0版本添加了缓存支持，以下内容是对Android官方文档的一个总结，有误之处还望指正。

 

 

HttpRespnseCache 类在Android 4.0 版本添加支持，支持 HttpURLConnection 和 HttpsURLConnection，但不支持DefaultHttpClient和AndroidHttpClient。

 

1.在程序开启的时候设定需要缓存，并设定缓存目录和缓存文件大小，例如：（最好把缓存目录设定在外部存储）

 

protectedvoid onCreate(Bundle savedInstanceState){
...

try{
File httpCacheDir =newFile(context.getCacheDir(),"http");
long httpCacheSize =10*1024*1024;// 10 MiB
HttpResponseCache.install(httpCacheDir, httpCacheSize);
catch(IOException e){
Log.i(TAG,"HTTP response cache installation failed:"+ e);
}
}

protectedvoid onStop(){
...

HttpResponseCache cache =HttpResponseCache.getInstalled();
if(cache !=null){
           cache.flush();
}
}}

   1.例如点击“刷新”按钮，或者手动刷新，这时候要强制刷新，就需要添加“no-cache”指令

connection.addRequestProperty("Cache-Control","no-cache");

   2.如果只需要强制缓存的响应由服务器进行验证，使用更高效的“max-age=0”指令来代替：

connection.addRequestProperty("Cache-Control","max-age=0");

try{
         connection.addRequestProperty("Cache-Control","only-if-cached");
InputStream cached = connection.getInputStream();
// the resource was cached! show it
catch(FileNotFoundException e){
// the resource was not cached
}
}

   4.你还可以设定缓存的有效时间

 

int maxStale =60*60*24*28;// tolerate 4-weeks stale
         connection.addRequestProperty("Cache-Control","max-stale="+ maxStale);

try{
File httpCacheDir =newFile(context.getCacheDir(),"http");
long httpCacheSize =10*1024*1024;// 10 MiB
Class.forName("android.net.http.HttpResponseCache")
.getMethod("install",File.class,long.class)
.invoke(null, httpCacheDir, httpCacheSize);
catch(Exception httpResponseCacheNotAvailable){
}}