需要Android中的HttpResponseCache示例

Question

嗨我正在尝试使用Android 4中引入的HttpResponseCache.文档确实谈到了如何安装缓存,但我完全失去了如何缓存从网上下载的图像.早期我使用的是DiskLruCache来缓存它们.有人会指出我使用HttpResponseCache的工作代码的一些例子.

编辑: - 有人能告诉我这里做错了什么: -

MainActivity.java
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final long httpCacheSize = 10 * 1024 * 1024; // 10 MiB
    final File httpCacheDir = new File(getCacheDir(), "http");
    try {
        Class.forName("android.net.http.HttpResponseCache")
            .getMethod("install", File.class, long.class)
            .invoke(null, httpCacheDir, httpCacheSize);
        Log.v(TAG,"cache set up");
    } catch (Exception httpResponseCacheNotAvailable) {
        Log.v(TAG, "android.net.http.HttpResponseCache not available, probably because we're running on a pre-ICS version of Android. Using com.integralblue.httpresponsecache.HttpHttpResponseCache.");
        try{
            com.integralblue.httpresponsecache.HttpResponseCache.install(httpCacheDir, httpCacheSize);
        }catch(Exception e){
            Log.v(TAG, "Failed to set up com.integralblue.httpresponsecache.HttpResponseCache");
        }
    }
    TheMainListFrag gf=(TheMainListFrag) getSupportFragmentManager().findFragmentByTag("thelistfrags");
    if(gf==null){
        gf=TheMainListFrag.newInstance();
        FragmentTransaction ft=getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.thelefty, gf,"thelistfrags");
        ft.commit();
    }
}

然后在TheMainListFrag的加载器中,我执行以下操作: -

public ArrayList<HashMap<String,String>> loadInBackground() {
    String datafromServer = null;
    ArrayList<HashMap<String,String>> al = new ArrayList<HashMap<String,String>>();
    try {
        String url = "someurl";
        HttpURLConnection urlConnection = (HttpURLConnection) new URL(url).openConnection();

        urlConnection.setRequestProperty("Accept", "application/json");
        InputStream is = new BufferedInputStream(urlConnection.getInputStream());
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = br.readLine()) != null) {
            sb.append(line);
        }
        datafromServer=sb.toString();
        Log.v("fromthread",datafromServer);
        // etc 
                    //etc

    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (Exception e) {
        Log.v("fromthread", e.getClass() + "--" + e.getMessage());
    }

    return al;
}

当我连接到互联网,它工作正常,并在目录http-上面命名的缓存目录,我也可以看到文件.但是,当我没有连接到互联网时,数据拒绝加载.

当我从网络加载图像时,我看到名为.tmp的缓存文件,我认为这些文件被称为脏盘,因为DiskLruCache.

如果您希望我提供任何其他信息,请与我们联系

Answer 1

从部分强制缓存响应的上HttpResponseCache文档:

有时,如果资源立即可用,您将需要显示资源,但不会显示.这可以使用,以便您的应用程序可以在等待下载最新数据时显示某些内容.要将请求限制为本地缓存的资源,请添加 only-if-cached指令:

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
}

在陈旧响应优于无响应的情况下,此技术可以更好地工作.要允许过时的缓存响应,请使用max-stale具有最大过时(以秒为单位)的 指令:

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