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){
       }}