blocks|key|1377039|text|现在的笑点是:使用系统缓存。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1377040|URL+url+=+new+URL(strUrl);
URLConnection+connection+=+url.openConnection();
connection.setUseCaches(true);
Object+response+=+connection.getContent();
if+(response+instanceof+Bitmap)+{
++Bitmap+bitmap+=+(Bitmap)response;
}+|code-block|syntax|javascript|1377041|提供内存和闪存rom缓存，与浏览器共享。|1377042|grr。我希望在我写自己的缓存管理器之前有人告诉我。|1377043|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

And now the punchline: use the system cache.

<pre><code>URL url = new URL(strUrl);
URLConnection connection = url.openConnection();
connection.setUseCaches(true);
Object response = connection.getContent();
if (response instanceof Bitmap) {
 Bitmap bitmap = (Bitmap)response;
} 
</code></pre>

Provides both memory and flash-rom cache, shared with the browser.

grr. I wish somebody had told ME that before i wrote my own cache manager.

blocks|key|1377085|text|关于上面优雅的connection.setUseCaches解决方案:可悲的是，如果没有一些额外的努力，它将无法工作。您将需要使用ResponseCache.setDefault安装ResponseCache。否则，HttpURLConnection将静默忽略setUseCaches(true)位。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1377086|有关详细信息，请参阅FileResponseCache.java顶部的注释：|1377087|http://libs-for-android.googlecode.com/svn/reference/com/google/android/filecache/FileResponseCache.html|1377088|(我会在评论中发表这篇文章，但我显然没有足够的SO+karma。)|1377089|entityMap|0|LINK|mutability|MUTABLE|url^0|7|N|1T|O|2J|D|30|H|3M|I|0|A|M|0|0|2W|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|16|8|@]|D|@$9|17|A|18|1|19]]|E|$]]|$1|J|3|K|5|6|7|1A|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|M|$N|$5|O|P|Q|E|$R|I]]]]

Regarding the elegant <code>connection.setUseCaches</code> solution above: sadly, it won't work without some additional effort. You will need to install a <code>ResponseCache</code> using <code>ResponseCache.setDefault</code>. Otherwise, <code>HttpURLConnection</code> will silently ignore the <code>setUseCaches(true)</code> bit.

See the comments at the top of <code>FileResponseCache.java</code> for details:

<a href="http://libs-for-android.googlecode.com/svn/reference/com/google/android/filecache/FileResponseCache.html" rel="noreferrer">http://libs-for-android.googlecode.com/svn/reference/com/google/android/filecache/FileResponseCache.html</a>

(I'd post this in a comment, but I apparently don't have enough SO karma.)

blocks|key|1376931|text|要下载图像并保存到存储卡，您可以这样做。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1376932|//First+create+a+new+URL+object+
URL+url+=+new+URL("http://www.google.co.uk/logos/holiday09_2.gif")

//Next+create+a+file,+the+example+below+will+save+to+the+SDCARD+using+JPEG+format
File+file+=+new+File("/sdcard/example.jpg");

//Next+create+a+Bitmap+object+and+download+the+image+to+bitmap
Bitmap+bitmap+=+BitmapFactory.decodeStream(url.openStream());

//Finally+compress+the+bitmap,+saving+to+the+file+previously+created
bitmap.compress(CompressFormat.JPEG,+100,+new+FileOutputStream(file));|code-block|syntax|javascript|1376933|不要忘记将Internet权限添加到您的清单中：|1376934|<uses-permission+android:name="android.permission.INTERNET"+/>|1376935|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

To download an image and save to the memory card you can do it like this.

<pre><code>//First create a new URL object 
URL url = new URL("http://www.google.co.uk/logos/holiday09_2.gif")

//Next create a file, the example below will save to the SDCARD using JPEG format
File file = new File("/sdcard/example.jpg");

//Next create a Bitmap object and download the image to bitmap
Bitmap bitmap = BitmapFactory.decodeStream(url.openStream());

//Finally compress the bitmap, saving to the file previously created
bitmap.compress(CompressFormat.JPEG, 100, new FileOutputStream(file));
</code></pre>

Don't forget to add the Internet permission to your manifest:

<pre><code>&lt;uses-permission android:name="android.permission.INTERNET" /&gt;
</code></pre>

blocks|key|1161833|text|我会考虑使用droidfu的图像缓存。它同时实现了内存中和基于磁盘的图像缓存。您还可以获得一个利用ImageCache库的WebImageView。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1161834|以下是http://brainflush.wordpress.com/2009/11/23/droid-fu-part-2-webimageview-and-webgalleryadapter/和droidfu的完整描述：|offset|length|1161835|entityMap|0|LINK|mutability|MUTABLE|url|http://brainflush.wordpress.com/2009/11/23/droid-fu-part-2-webimageview-and-webgalleryadapter/^0|0|3|2M|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

I would consider using droidfu's image cache. It implements both an in-memory and disk-based image cache. You also get a WebImageView that takes advantage of the ImageCache library.

Here is the full description of droidfu and WebImageView:
<a href="http://brainflush.wordpress.com/2009/11/23/droid-fu-part-2-webimageview-and-webgalleryadapter/" rel="nofollow noreferrer">http://brainflush.wordpress.com/2009/11/23/droid-fu-part-2-webimageview-and-webgalleryadapter/</a>

blocks|key|1161996|text|我试过SoftReferences，它们在安卓中的回收力度太大了，我觉得使用它们没有意义|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1161997|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I've tried SoftReferences, they are too aggressively reclaimed in android that I felt there was no point using them

blocks|key|1377280|text|正如雷兔建议的那样，ImageDownloader是最适合这项工作的。我还发现这个类在以下位置有一些细微的变化：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1377281|http://theandroidcoder.com/utilities/android-image-download-and-caching/|offset|length|1377282|两者的主要区别在于，ImageDownloader使用的是安卓缓存系统，而修改后的版本使用了内部和外部存储作为缓存，将缓存的图片无限期地保存下来，或者直到用户手动移除。作者还提到了Android+2.1的兼容性。|1377283|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|20|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@$D|Q|E|R|1|S]]|A|$]]|$1|F|3|G|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|C]]]]

As Thunder Rabbit suggested, ImageDownloader is the best one for the job. I also found a slight variation of the class at:

<a href="http://theandroidcoder.com/utilities/android-image-download-and-caching/" rel="nofollow noreferrer">http://theandroidcoder.com/utilities/android-image-download-and-caching/</a>

The main difference between the two is that the ImageDownloader uses the Android caching system, and the modified one uses internal and external storage as caching, keeping the cached images indefinitely or until the user removes it manually. The author also mentions Android 2.1 compatibility.

blocks|key|1162036|text|这是Joe的一个好接球。上面的代码示例有两个问题-一个-响应对象不是位图的实例(当我的URL引用jpg时，比如http:\website.com\image.jpg，它是一个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1162037|org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl$LimitedInputStream).|1162038|其次，正如Joe指出的那样，如果没有配置响应缓存，则不会发生缓存。Android开发人员只能使用自己的缓存。这是一个这样做的例子，但它只缓存在内存中，这实际上不是完整的解决方案。|1162039|http://codebycoffee.com/2010/06/29/using-responsecache-in-an-android-app/|offset|length|1162040|URLConnection缓存接口介绍如下：|1162041|http://download.oracle.com/javase/6/docs/technotes/guides/net/http-cache.html|1162042|我仍然认为这是一个可行的解决方案--但是你仍然需要写一个缓存。听起来很有趣，但我更喜欢写特性。|1162043|entityMap|0|LINK|mutability|MUTABLE|url|1^0|0|0|0|0|21|0|0|0|0|25|1|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Z|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|10|8|@]|9|@$H|11|I|12|1|13]]|A|$]]|$1|J|3|K|5|6|7|14|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|15|8|@]|9|@$H|16|I|17|1|18]]|A|$]]|$1|N|3|O|5|6|7|19|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|G]]|W|$5|S|T|U|A|$V|M]]]]

This is a good catch by Joe. The code example above has two problems - one - the response object isn't an instance of Bitmap (when my URL references a jpg, like http:\website.com\image.jpg, its a

org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl$LimitedInputStream).

Second, as Joe points out, no caching occurs without a response cache being configured. Android developers are left to roll their own cache. Here's an example for doing so, but it only caches in memory, which really isn't the full solution.

<a href="http://codebycoffee.com/2010/06/29/using-responsecache-in-an-android-app/">http://codebycoffee.com/2010/06/29/using-responsecache-in-an-android-app/</a>

The URLConnection caching API is described here:

<a href="http://download.oracle.com/javase/6/docs/technotes/guides/net/http-cache.html">http://download.oracle.com/javase/6/docs/technotes/guides/net/http-cache.html</a>

I still think this is an OK solution to go this route - but you still have to write a cache. Sounds like fun, but I'd rather write features.

blocks|key|1162183|text|对我来说真正起作用的是在我的主类上设置ResponseCache：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1162184|try+{
+++File+httpCacheDir+=+new+File(getApplicationContext().getCacheDir(),+"http");
+++long+httpCacheSize+=+10+*+1024+*+1024;+//+10+MiB
+++HttpResponseCache.install(httpCacheDir,+httpCacheSize);
}+catch+(IOException+e)+{+}+|code-block|syntax|javascript|1162185|和|1162186|connection.setUseCaches(true);|1162187|下载位图时。|1162188|http://practicaldroid.blogspot.com/2013/01/utilizing-http-response-cache.html|offset|length|1162189|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|0|0|0|25|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Z|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|11|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|12|8|@]|9|@$O|13|P|14|1|15]]|A|$]]|$1|Q|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|N]]]]

What actually worked for me was setting ResponseCache on my Main class:

<pre><code>try {
 File httpCacheDir = new File(getApplicationContext().getCacheDir(), "http");
 long httpCacheSize = 10 * 1024 * 1024; // 10 MiB
 HttpResponseCache.install(httpCacheDir, httpCacheSize);
} catch (IOException e) { } 
</code></pre>

and 

<pre><code>connection.setUseCaches(true);
</code></pre>

when downloading bitmap.

<a href="http://practicaldroid.blogspot.com/2013/01/utilizing-http-response-cache.html" rel="nofollow">http://practicaldroid.blogspot.com/2013/01/utilizing-http-response-cache.html</a>

blocks|key|1162105|text|Google的libs-+for+-android有一个很好的库来管理图像和文件缓存。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1162106|http://code.google.com/p/libs-for-android/|offset|length|1162107|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|16|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@$D|O|E|P|1|Q]]|A|$]]|$1|F|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|C]]]]

Google's libs-for-android has a nice libraries for managing image and file cache.

<a href="http://code.google.com/p/libs-for-android/" rel="nofollow">http://code.google.com/p/libs-for-android/</a>

blocks|key|1162073|text|我已经在这个问题上挣扎了一段时间；使用SoftReferences的答案会很快丢失他们的数据。建议实例化RequestCache的答案太混乱了，而且我永远找不到完整的示例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1162074|但是ImageDownloader.java对我来说工作得很棒。它使用HashMap，直到达到容量或清除超时，然后将所有内容移动到SoftReference，从而使用这两种情况的最佳效果。|offset|length|1162075|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/resources/samples/XmlAdapters/src/com/example/android/xmladapters/ImageDownloader.html^0|0|2|K|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

I had been wrestling with this for some time; the answers using SoftReferences would lose their data too quickly. The answers that suggest instantiating a RequestCache were too messy, plus I could never find a full example.

But <a href="http://developer.android.com/resources/samples/XmlAdapters/src/com/example/android/xmladapters/ImageDownloader.html" rel="nofollow">ImageDownloader.java</a> works wonderfully for me. It uses a HashMap until the capacity is reached or until the purge timeout occurs, then things get moved to a SoftReference, thereby using the best of both worlds.

blocks|key|1162150|text|甚至是后来的回答，但我写了一个Android图像管理器，它透明地处理缓存(内存和磁盘)。代码在Github+https://github.com/felipecsl/Android-ImageManager上|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1162151|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/felipecsl/Android-ImageManager^0|1I|1D|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Even later answer, but I wrote an Android Image Manager that handles caching transparently (memory and disk). The code is on Github <a href="https://github.com/felipecsl/Android-ImageManager" rel="nofollow">https://github.com/felipecsl/Android-ImageManager</a>

blocks|key|1162229|text|回答晚了，但我认为这个库在缓存图像方面会有很大帮助：https://github.com/crypticminds/ColdStorage。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1162230|只需使用@LoadCache(R.id.id_of_my_image_view，"URL_to_downlaod_image_from)注释ImageView，它将负责下载图像并将其加载到图像视图中。您还可以指定占位符图像和加载动画。|1162231|此处提供了注释的详细文档:-+https://github.com/crypticminds/ColdStorage/wiki/@LoadImage-annotation|1162232|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/crypticminds/ColdStorage|1|https://github.com/crypticminds/ColdStorage/wiki/@LoadImage-annotation^0|Q|17|0|0|0|F|1Y|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|H|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]|P|$5|K|L|M|C|$N|Q]]]]

Late answer but I think this library will help a lot with caching images :
<a href="https://github.com/crypticminds/ColdStorage" rel="nofollow noreferrer">https://github.com/crypticminds/ColdStorage</a>.

Simply annotate the ImageView with 
@LoadCache(R.id.id_of_my_image_view, "URL_to_downlaod_image_from) and it will take care of downloading the image and loading it into the image view. You can also specify a placeholder image and loading animation.

Detailed documentation of the annotation is present here :-
<a href="https://github.com/crypticminds/ColdStorage/wiki/@LoadImage-annotation" rel="nofollow noreferrer">https://github.com/crypticminds/ColdStorage/wiki/@LoadImage-annotation</a>

How can I cache images after they are downloaded from web?

问Android镜像缓存
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