需要的Htt presponseCache在Android的一个例子 [英] Need an example of HttpResponseCache in Android

问题描述

您好我想使用的Htt的presponseCache在安卓4.文档介绍了不说清楚有关如何安装的缓存，但我在如何缓存图片完全丧失从net.Earlier我下载是使用DiskLruCache对其进行缓存。会有人指出我对工作code一些例子，其中的Htt presponseCache已被使用。

编辑： - 谁能告诉我什么，我做错了什么： -

  MainActivity.java
公共无效的onCreate（包savedInstanceState）{
    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.activity_main）;
    最终长httpCacheSize = 10 * 1024 * 1024; // 10 MIB
    最终文件httpCacheDir =新的文件（getCacheDir（），HTTP）;
    尝试 {
        的Class.forName（android.net.http.Htt presponseCache）
            .getMethod（安装，File.class，long.class）
            .invoke（NULL，httpCacheDir，httpCacheSize）;
        Log.v（TAG，缓存设置）;
    }赶上（例外HTT presponseCacheNotAvailable）{
        Log.v（TAG，android.net.http.Htt presponseCache不可用，可能是因为我们正在运行在Android上的pre-ICS版本。使用com.integralblue.htt presponsecache。 HttpHtt presponseCache）。
        尝试{
            com.integralblue.htt presponsecache.Htt presponseCache.install（httpCacheDir，httpCacheSize）;
        }赶上（例外五）{
            Log.v（TAG，无法设置com.integralblue.htt presponsecache.Htt presponseCache）;
        }
    }
    TheMainListFrag GF =（TheMainListFrag）getSupportFragmentManager（）findFragmentByTag（thelistfrags）。
    如果（GF == NULL）{
        GF = TheMainListFrag.newInstance（）;
        FragmentTransaction英尺= getSupportFragmentManager（）的BeginTransaction（）。
        ft.replace（R.id.thelefty，广发，thelistfrags）;
        ft.commit（）;
    }
}
 

然后在TheMainListFrag的装载机，我做了如下： -

 公开的ArrayList＆LT; HashMap的＆LT;字符串，字符串＆GT;＆GT; loadInBackground（）{
    字符串datafromServer = NULL;
    ArrayList的＆LT; HashMap的＆LT;字符串，字符串＆GT;＆GT;人=新的ArrayList＆LT; HashMap的＆LT;字符串，字符串＆GT;＆GT;（）;
    尝试 {
        字符串URL =someurl;
        HttpURLConnection的的URLConnection =（HttpURLConnection类）新的网址（URL）.openConnection（）;

        urlConnection.setRequestProperty（接受，应用/ JSON）;
        InputStream的是=新的BufferedInputStream（urlConnection.getInputStream（））;
        的BufferedReader BR =新的BufferedReader（新InputStreamReader的（是））;
        StringBuilder的SB =新的StringBuilder（）;
        串线= NULL;
        而（（行= br.readLine（））！= NULL）{
            sb.append（线）;
        }
        datafromServer = sb.toString（）;
        Log.v（fromthread，datafromServer）;
        // 等等
                    //等等

    }赶上（MalformedURLException异常E）{
        // TODO自动生成的catch块
        e.printStackTrace（）;
    }赶上（IOException异常E）{
        // TODO自动生成的catch块
        e.printStackTrace（）;
    }赶上（例外五）{
        Log.v（fromthread，e.getClass（）+ - + e.getMessage（））;
    }

    返回人;
}
 

当我连接到互联网，它工作正常，并在目录中的HTTP-上述命名的缓存目录，我可以看到文件了。但是，当我没有连接到互联网，数据拒绝加载。

当我从网上载入图像，我看到命名为.tmp文件的缓存文件，我相信被称为肮脏按DiskLruCache。

请让我知道，如果有任何其他的信息，你要我提供

解决方案

这部分的强制缓存响应上的 Htt的presponseCache文档：

  

有时候你会想显示的资源（如果可用）   马上，而不是其他。这可以用来使你的应用程序   可以显示的事的同时等待最新数据是   下载。要限制的请求，本地缓存的资源，加上   只，如果缓存指令：

 尝试{
    connection.addRequestProperty（缓存控制，只有-IF-缓存）;
    InputStream的缓存= connection.getInputStream（）;
    //资源被缓存！展示下
}赶上（FileNotFoundException异常E）{
    //资源没有缓存
}
 

  

该技术的工作原理，甚至更好的情况下，一个陈旧的响应   比没有反应好。为了使陈旧的缓存响应，使用    MAX-陈旧指令以秒的最大过时：

  INT maxStale = 60 * 60 * 24 * 28; //容忍4周陈旧
connection.addRequestProperty（缓存控制，MAX-陈旧=+ maxStale）;
 

Hi I am trying to use the HttpResponseCache introduced in Android 4.The docs do talk clearly about how to install the cache but I am at a complete loss on how to cache Images downloaded from the net.Earlier I was using the DiskLruCache to cache them. Would anyone point me towards some examples of working code where HttpResponseCache has been used..

Edit:- Can someone tell me what I am doing wrong here:-

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();
    }
}

Then in the loader of TheMainListFrag, I do the below:-

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;
}

When i am connected to internet, it works fine, and in the directory http-the cache directory named above, i can see the files too. But when I am not connected to the internet, the data refuses to load.

When i load images from the net, i see the cache files named as .tmp , which i believe are termed as dirty as per DiskLruCache.

Please let me know if there is any other info that you want me to provide

解决方案

From the section Force a Cache Response on the HttpResponseCache documentation:

Sometimes you'll want to show resources if they are available immediately, but not otherwise. This can be used so your application can show something while waiting for the latest data to be downloaded. To restrict a request to locally-cached resources, add the only-if-cached directive:

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
}

This technique works even better in situations where a stale response is better than no response. To permit stale cached responses, use the max-stale directive with the maximum staleness in seconds:

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

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