Android Webview - 彻底清除缓存 [英] Android Webview - Completely Clear the Cache

问题描述

我的一个活动中有一个 WebView，当它加载网页时，该页面会从 Facebook 收集一些背景数据.

I have a WebView in one of my Activities, and when it loads a webpage, the page gathers some background data from Facebook.

但我看到的是，每次打开和刷新应用程序时，应用程序中显示的页面都是相同的.

What I'm seeing though, is the page displayed in the application is the same on each time the app is opened and refreshed.

我已经尝试将 WebView 设置为不使用缓存并清除 WebView 的缓存和历史记录.

I've tried setting the WebView not to use cache and clear the cache and history of the WebView.

我也遵循了这里的建议:如何为 WebView 清空缓存?

I've also followed the suggestion here: How to empty cache for WebView?

但是这些都不起作用，有没有人知道我可以克服这个问题，因为它是我的应用程序的重要组成部分.

But none of this works, does anyone have any ideas of I can overcome this problem because it is a vital part of my application.

    mWebView.setWebChromeClient(new WebChromeClient()
    {
           public void onProgressChanged(WebView view, int progress)
           {
               if(progress >= 100)
               {
                   mProgressBar.setVisibility(ProgressBar.INVISIBLE);
               }
               else
               {
                   mProgressBar.setVisibility(ProgressBar.VISIBLE);
               }
           }
    });
    mWebView.setWebViewClient(new SignInFBWebViewClient(mUIHandler));
    mWebView.getSettings().setJavaScriptEnabled(true);
    mWebView.clearHistory();
    mWebView.clearFormData();
    mWebView.clearCache(true);

    WebSettings webSettings = mWebView.getSettings();
    webSettings.setCacheMode(WebSettings.LOAD_NO_CACHE);

    Time time = new Time();
    time.setToNow();

    mWebView.loadUrl(mSocialProxy.getSignInURL()+"?time="+time.format("%Y%m%d%H%M%S"));

所以我实现了第一个建议(虽然将代码更改为递归)

So I implemented the first suggestion (Although changed the code to be recursive)

private void clearApplicationCache() {
    File dir = getCacheDir();

    if (dir != null && dir.isDirectory()) {
        try {
            ArrayList<File> stack = new ArrayList<File>();

            // Initialise the list
            File[] children = dir.listFiles();
            for (File child : children) {
                stack.add(child);
            }

            while (stack.size() > 0) {
                Log.v(TAG, LOG_START + "Clearing the stack - " + stack.size());
                File f = stack.get(stack.size() - 1);
                if (f.isDirectory() == true) {
                    boolean empty = f.delete();

                    if (empty == false) {
                        File[] files = f.listFiles();
                        if (files.length != 0) {
                            for (File tmp : files) {
                                stack.add(tmp);
                            }
                        }
                    } else {
                        stack.remove(stack.size() - 1);
                    }
                } else {
                    f.delete();
                    stack.remove(stack.size() - 1);
                }
            }
        } catch (Exception e) {
            Log.e(TAG, LOG_START + "Failed to clean the cache");
        }
    }
}

然而，这仍然没有改变页面显示的内容.在我的桌面浏览器上，我得到了与 WebView 中生成的网页不同的 html 代码，所以我知道 WebView 必须缓存在某处.

However this still hasn't changed what the page is displaying. On my desktop browser I am getting different html code to the web page produced in the WebView so I know the WebView must be caching somewhere.

在 IRC 频道上，有人指出我修复了从 URL 连接中删除缓存的问题，但目前还看不到如何将其应用于 WebView.

On the IRC channel I was pointed to a fix to remove caching from a URL Connection but can't see how to apply it to a WebView yet.

http://www.androidsnippets.org/snippets/45/

如果我删除我的应用程序并重新安装它，我可以将网页恢复到最新，即非缓存版本.主要问题是网页中的链接发生了变化，所以网页的前端完全没有变化.

If I delete my application and re-install it, I can get the webpage back up to date, i.e. a non-cached version. The main problem is the changes are made to links in the webpage, so the front end of the webpage is completely unchanged.

推荐答案

以上由 Gaunt Face 发布的编辑过的代码片段包含一个错误，即如果某个目录因为其中一个文件无法删除而导致删除失败，该代码将保留在无限循环中重试.我将它重写为真正的递归，并添加了一个 numDays 参数，以便您可以控制必须修剪的文件的年龄:

The edited code snippet above posted by Gaunt Face contains an error in that if a directory fails to delete because one of its files cannot be deleted, the code will keep retrying in an infinite loop. I rewrote it to be truly recursive, and added a numDays parameter so you can control how old the files must be that are pruned:

//helper method for clearCache() , recursive
//returns number of deleted files
static int clearCacheFolder(final File dir, final int numDays) {

    int deletedFiles = 0;
    if (dir!= null && dir.isDirectory()) {
        try {
            for (File child:dir.listFiles()) {

                //first delete subdirectories recursively
                if (child.isDirectory()) {
                    deletedFiles += clearCacheFolder(child, numDays);
                }

                //then delete the files and subdirectories in this dir
                //only empty directories can be deleted, so subdirs have been done first
                if (child.lastModified() < new Date().getTime() - numDays * DateUtils.DAY_IN_MILLIS) {
                    if (child.delete()) {
                        deletedFiles++;
                    }
                }
            }
        }
        catch(Exception e) {
            Log.e(TAG, String.format("Failed to clean the cache, error %s", e.getMessage()));
        }
    }
    return deletedFiles;
}

/*
 * Delete the files older than numDays days from the application cache
 * 0 means all files.
 */
public static void clearCache(final Context context, final int numDays) {
    Log.i(TAG, String.format("Starting cache prune, deleting files older than %d days", numDays));
    int numDeletedFiles = clearCacheFolder(context.getCacheDir(), numDays);
    Log.i(TAG, String.format("Cache pruning completed, %d files deleted", numDeletedFiles));
}

希望对其他人有用:)

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