Question

我有一个Android应用程序，只是一个网站。我希望该应用程序缓存网站页面以供离线使用。

我正在做一个简单的测试，看看缓存是否正常工作，但不幸的是，它无法加载我以前在线模式下加载的页面，当离线时。为了使事情更清楚，我在在线模式下加载以下2页。

webView.loadUrl("http://www.bmimobile.co.uk/why-bmi.php", getHeaders());
webView.loadUrl("http://www.bmimobile.co.uk/", getHeaders());

我希望＆＃34; why-bmi.php＆＃34;页面加载到缓存以及后续页面http://www.bmimobile.co.uk/。后一页上有一个链接，指的是第一页。如果我然后退出应用并关闭网络适配器，请返回应用程序＆＃34; http://www.bmimobile.co.uk/＆＃34;页面显示但是当我点击＆＃34; why-bmi＆＃34;链接该页面不显示。我简短的吐司信息显示＆＃34;错误加载页面＆＃34;。

有人能告诉我为什么webview没有缓存加载页面以供以后离线使用吗？

这是主要活动，我已经扩展了定义appcachepath的Application对象。

提前致谢

马特

package uk.bmi.mobile;

import java.io.File;
import java.util.HashMap;
import java.util.Map;
import android.app.Activity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.util.Log;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;



public class MainActivity extends Activity {


    private WebView webView;
    private static final String TAG = MainActivity.class.getSimpleName();
    ApplicationExt bmiAppObj;


    //instruct server to set it's headers to make resources cachable
    private Map<String, String> getHeaders() {
        Map<String, String> headers = new HashMap<String, String>();
        headers.put("IS_ALEX_APP", "1");
        return headers;
    }


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Log.e(TAG, "in onCreate in mainactivity");



    }      //end of oncreate


    private boolean isNetworkAvailable() {
        ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
        return activeNetworkInfo != null;
    }



    @Override
    protected void onResume() {
        super.onResume();

        Log.e(TAG, "in onResume in mainactivity");
        webView = (WebView)findViewById(R.id.webView1);
        bmiAppObj = (ApplicationExt)getApplication();


        if(isNetworkAvailable() == true){

            webView.getSettings().setSupportZoom(true);
            webView.getSettings().setBuiltInZoomControls(true);
            webView.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);
            webView.setScrollbarFadingEnabled(true);
            webView.getSettings().setLoadsImagesAutomatically(true);
            webView.getSettings().setDomStorageEnabled(true);
            webView.getSettings().setAppCacheEnabled(true);
            // Set cache size to 8 mb by default. should be more than enough
            webView.getSettings().setAppCacheMaxSize(1024*1024*8);
            // This next one is crazy. It's the DEFAULT location for your app's cache
            // But it didn't work for me without this line.
            // UPDATE: no hardcoded path. Thanks to Kevin Hawkins
            String appCachePath = getApplicationContext().getCacheDir().getAbsolutePath();
            Log.e(TAG, "appCachePath = " + appCachePath);
            webView.getSettings().setAppCachePath(appCachePath);
            webView.getSettings().setAllowFileAccess(true);

            webView.getSettings().setJavaScriptEnabled(true);

            // Load the URLs inside the WebView, not in the external web browser
            webView.setWebViewClient(new WebViewClient());  
            webView.getSettings().setCacheMode(WebSettings.LOAD_DEFAULT);


            webView.loadUrl("http://www.bmimobile.co.uk/why-bmi.php", getHeaders());
            webView.loadUrl("http://www.bmimobile.co.uk/", getHeaders());


            }else{

                webView.getSettings().setSupportZoom(true);
                webView.getSettings().setBuiltInZoomControls(true);
                webView.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);
                webView.setScrollbarFadingEnabled(true);
                webView.getSettings().setLoadsImagesAutomatically(true);
                webView.getSettings().setDomStorageEnabled(true);
                webView.getSettings().setAppCacheEnabled(true);
                // Set cache size to 8 mb by default. should be more than enough
                webView.getSettings().setAppCacheMaxSize(1024*1024*8);
                // This next one is crazy. It's the DEFAULT location for your app's cache
                // But it didn't work for me without this line.
                // UPDATE: no hardcoded path. Thanks to Kevin Hawkins
                String appCachePath = getApplicationContext().getCacheDir().getAbsolutePath();
                Log.e(TAG, "appCachePath = " + appCachePath);
                webView.getSettings().setAppCachePath(appCachePath);
                webView.getSettings().setAllowFileAccess(true);

                webView.getSettings().setJavaScriptEnabled(true);



                // Load the URLs inside the WebView, not in the external web browser
                webView.setWebViewClient(new WebViewClient());  



                webView.getSettings().setCacheMode(WebSettings.LOAD_CACHE_ONLY);

                webView.loadUrl("http://www.bmimobile.co.uk/", getHeaders());


            }


    }






    @Override
    public File getCacheDir()
    {
        // NOTE: this method is used in Android 2.1
        Log.e(TAG, "getcachedir");
        return getApplicationContext().getCacheDir();
    }

    @Override
    protected void onSaveInstanceState(Bundle outState)
    {
        super.onSaveInstanceState(outState);

        // Save the state of the WebView
        webView.saveState(outState);
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState)
    {
        super.onRestoreInstanceState(savedInstanceState);

        // Restore the state of the WebView
        webView.restoreState(savedInstanceState);
    }



}//end of mainActivity

package uk.bmi.mobile;

import java.io.File;

import android.app.Application;
import android.os.Environment;
import android.util.Log;

public class ApplicationExt extends Application
{
    private static final String TAG = ApplicationExt.class.getSimpleName();
    // NOTE: the content of this path will be deleted
    //       when the application is uninstalled (Android 2.2 and higher)
    protected File extStorageAppBasePath;

    protected File extStorageAppCachePath;

    Webservice webservice;
    BmiDB bmiDb;

    @Override
    public void onCreate()
    {
        super.onCreate();
         Log.e(TAG, "inside appext");

         webservice = new Webservice(this);
         bmiDb = new BmiDB(this);
        // Check if the external storage is writeable
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()))
        {

            // Retrieve the base path for the application in the external storage
            File externalStorageDir = Environment.getExternalStorageDirectory();

            if (externalStorageDir != null)
            {
                // {SD_PATH}/Android/data/com.devahead.androidwebviewcacheonsd
                extStorageAppBasePath = new File(externalStorageDir.getAbsolutePath() +
                    File.separator + "Android" + File.separator + "data" +
                    File.separator + getPackageName());
            }

            if (extStorageAppBasePath != null)
            {
                // {SD_PATH}/Android/data/com.devahead.androidwebviewcacheonsd/cache
                extStorageAppCachePath = new File(extStorageAppBasePath.getAbsolutePath() +
                    File.separator + "cache");

                boolean isCachePathAvailable = true;

                if (!extStorageAppCachePath.exists())
                {
                    // Create the cache path on the external storage
                    isCachePathAvailable = extStorageAppCachePath.mkdirs();
                }

                if (!isCachePathAvailable)
                {
                    // Unable to create the cache path
                    extStorageAppCachePath = null;
                }
            }
        }
    }//end of onCreate

    @Override
    public File getCacheDir()
    {
        // NOTE: this method is used in Android 2.2 and higher

        if (extStorageAppCachePath != null)
        {
            // Use the external storage for the cache
            Log.e(TAG, "extStorageAppCachePath = " + extStorageAppCachePath);
            return extStorageAppCachePath;
        }
        else
        {
            // /data/data/com.devahead.androidwebviewcacheonsd/cache
            return super.getCacheDir();
        }
    }
}

。这是应用程序首次以在线模式加载时的日志记录

02-16 08:38:52.744: I/NONPRIME(8871): <CallBackProxy> Send to WebViewClient.
02-16 08:38:56.314: D/skia(8871): ----- started: [1 325] http://www.bmimobile.co.uk/images/mobile/bg-index.png
02-16 08:38:56.499: D/skia(8871): ----- started: [1 64] http://www.bmimobile.co.uk/CubeCore/modules/cubeMobile/images/bg-black-bar.png
02-16 08:38:56.509: D/skia(8871): ----- started: [26 20] http://www.bmimobile.co.uk/images/mobile/home-icon.png
02-16 08:38:56.529: D/skia(8871): ----- started: [275 189] http://www.bmimobile.co.uk/images/mobile/home-img.png
02-16 08:38:56.549: D/skia(8871): ----- started: [320 450] http://www.bmimobile.co.uk/images/mobile/welcome/bg-welcome.jpg
02-16 08:38:56.554: D/skia(8871): ----- started: [270 38] http://www.bmimobile.co.uk/images/mobile/welcome/next.png
02-16 08:38:56.584: D/skia(8871): ----- started: [16 17] http://www.bmimobile.co.uk/images/mobile/why.png
02-16 08:38:56.584: D/skia(8871): ----- started: [18 17] http://www.bmimobile.co.uk/images/mobile/services.png
02-16 08:38:56.584: D/skia(8871): ----- started: [20 15] http://www.bmimobile.co.uk/images/mobile/visit.png
02-16 08:38:56.589: D/skia(8871): ----- started: [20 15] http://www.bmimobile.co.uk/images/mobile/consultants.png
02-16 08:38:56.589: D/skia(8871): ----- started: [13 19] http://www.bmimobile.co.uk/images/mobile/contact.png

这是当我从应用程序中关闭网络适配器然后在离线模式下返回应用程序时的日志记录。

02-16 08:41:37.799: E/MainActivity(8871): in onResume in mainactivity
02-16 08:41:37.804: E/ApplicationExt(8871): extStorageAppCachePath = /storage/sdcard0/Android/data/uk.bmi.mobile/cache
02-16 08:41:37.804: E/MainActivity(8871): appCachePath = /storage/sdcard0/Android/data/uk.bmi.mobile/cache
02-16 08:41:37.834: W/dalvikvm(8871): disableGcForExternalAlloc: false

[EDIT1] 实际上，仔细检查日志记录，在在线模式下加载时似乎已经改变了。以下是omline模式下的logcat。缓存存储似乎存在问题。

02-19 15:16:10.497: E/ApplicationExt(5467): inside appext
02-19 15:16:10.687: E/ApplicationExt(5467): extStorageAppCachePath = /storage/sdcard0/Android/data/uk.bmi.mobile/cache
02-19 15:16:10.722: E/MainActivity(5467): in onCreate in mainactivity
02-19 15:16:10.727: E/MainActivity(5467): in onResume in mainactivity
02-19 15:16:10.737: E/ApplicationExt(5467): extStorageAppCachePath = /storage/sdcard0/Android/data/uk.bmi.mobile/cache
02-19 15:16:10.737: E/MainActivity(5467): appCachePath = /storage/sdcard0/Android/data/uk.bmi.mobile/cache
02-19 15:16:10.792: E/(5467): file /data/data/com.nvidia.NvCPLSvc/files/driverlist.txt: not found!
02-19 15:16:10.792: I/(5467): Attempting to load EGL implementation /system/lib//egl/libEGL_tegra_impl
02-19 15:16:10.807: I/(5467): Loaded EGL implementation /system/lib//egl/libEGL_tegra_impl
02-19 15:16:10.842: I/(5467): Loading GLESv2 implementation /system/lib//egl/libGLESv2_tegra_impl
02-19 15:16:10.882: E/SQLiteLog(5467): (1) no such table: CacheGroups
02-19 15:16:10.882: D/WebKit(5467): ERROR: 
02-19 15:16:10.882: D/WebKit(5467): Application Cache Storage: failed to execute statement "DELETE FROM CacheGroups" error "no such table: CacheGroups"
02-19 15:16:10.882: D/WebKit(5467): external/webkit/Source/WebCore/loader/appcache/ApplicationCacheStorage.cpp(558) : bool WebCore::ApplicationCacheStorage::executeSQLCommand(const WTF::String&)
02-19 15:16:10.882: E/SQLiteLog(5467): (1) no such table: Caches
02-19 15:16:10.882: D/WebKit(5467): ERROR: 
02-19 15:16:10.882: D/WebKit(5467): Application Cache Storage: failed to execute statement "DELETE FROM Caches" error "no such table: Caches"
02-19 15:16:10.882: D/WebKit(5467): external/webkit/Source/WebCore/loader/appcache/ApplicationCacheStorage.cpp(558) : bool WebCore::ApplicationCacheStorage::executeSQLCommand(const WTF::String&)
02-19 15:16:10.882: E/SQLiteLog(5467): (1) no such table: Origins
02-19 15:16:10.882: D/WebKit(5467): ERROR: 
02-19 15:16:10.882: D/WebKit(5467): Application Cache Storage: failed to execute statement "DELETE FROM Origins" error "no such table: Origins"
02-19 15:16:10.882: D/WebKit(5467): external/webkit/Source/WebCore/loader/appcache/ApplicationCacheStorage.cpp(558) : bool WebCore::ApplicationCacheStorage::executeSQLCommand(const WTF::String&)
02-19 15:16:10.882: E/SQLiteLog(5467): (1) no such table: DeletedCacheResources
02-19 15:16:10.992: E/ApplicationExt(5467): extStorageAppCachePath = /storage/sdcard0/Android/data/uk.bmi.mobile/cache
02-19 15:16:11.022: W/dalvikvm(5467): disableGcForExternalAlloc: false
02-19 15:16:13.787: I/NONPRIME(5467): <CallBackProxy> Send to WebViewClient.
02-19 15:16:21.427: D/skia(5467): ----- started: [1 325] http://www.bmimobile.co.uk/images/mobile/bg-index.png
02-19 15:16:21.517: D/skia(5467): ----- started: [1 64] http://www.bmimobile.co.uk/CubeCore/modules/cubeMobile/images/bg-black-bar.png
02-19 15:16:21.542: D/skia(5467): ----- started: [26 20] http://www.bmimobile.co.uk/images/mobile/home-icon.png
02-19 15:16:21.577: D/skia(5467): ----- started: [275 189] http://www.bmimobile.co.uk/images/mobile/home-img.png
02-19 15:16:21.597: D/skia(5467): ----- started: [270 38] http://www.bmimobile.co.uk/images/mobile/welcome/next.png
02-19 15:16:21.677: D/skia(5467): ----- started: [16 17] http://www.bmimobile.co.uk/images/mobile/why.png
02-19 15:16:21.677: D/skia(5467): ----- started: [20 15] http://www.bmimobile.co.uk/images/mobile/visit.png
02-19 15:16:21.677: D/skia(5467): ----- started: [18 17] http://www.bmimobile.co.uk/images/mobile/services.png
02-19 15:16:21.687: D/skia(5467): ----- started: [20 15] http://www.bmimobile.co.uk/images/mobile/consultants.png
02-19 15:16:21.687: D/skia(5467): ----- started: [13 19] http://www.bmimobile.co.uk/images/mobile/contact.png
02-19 15:16:21.692: D/skia(5467): ----- started: [320 450] http://www.bmimobile.co.uk/images/mobile/welcome/bg-welcome.jpg

[注释] 如果我在在线模式下点击why-bmi按钮然后退出应用程序，关闭适配器然后再次单击why-bmi按钮然后它会显示＆＃34;错误加载页面＆＃34;消息。

但是，如果我更改为以下网址，则会显示我的SO页面。如果我单击指向我的赏金页面（此页面）的链接，然后离线，SO页面将按预期显示，但如果您在离线模式下单击赏金链接，则会显示。所以SO站点和bmi站点之间存在差异。

if(isNetworkAvailable() == true){

            webView.getSettings().setSupportZoom(true);
            webView.getSettings().setBuiltInZoomControls(true);
            webView.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);
            webView.setScrollbarFadingEnabled(true);
            webView.getSettings().setLoadsImagesAutomatically(true);
            webView.getSettings().setDomStorageEnabled(true);
            webView.getSettings().setAppCacheEnabled(true);
            // Set cache size to 8 mb by default. should be more than enough
            webView.getSettings().setAppCacheMaxSize(1024*1024*8);
            // This next one is crazy. It's the DEFAULT location for your app's cache
            // But it didn't work for me without this line.
            // UPDATE: no hardcoded path. Thanks to Kevin Hawkins
            String appCachePath = getApplicationContext().getCacheDir().getAbsolutePath();
            Log.e(TAG, "appCachePath = " + appCachePath);
            webView.getSettings().setAppCachePath(appCachePath);
            webView.getSettings().setAllowFileAccess(true);

            webView.getSettings().setJavaScriptEnabled(true);

            // Load the URLs inside the WebView, not in the external web browser
            webView.setWebViewClient(new WebViewClient());  
            webView.getSettings().setCacheMode(WebSettings.LOAD_DEFAULT);


            //webView.loadUrl("http://www.bmimobile.co.uk/why-bmi.php", getHeaders());
            //webView.loadUrl("http://www.bmimobile.co.uk/", getHeaders());

            webView.loadUrl("http://stackoverflow.com/users/532462/turtleboy?tab=bounties");
            webView.loadUrl("http://stackoverflow.com/users/532462/turtleboy");
            }else{

                webView.getSettings().setSupportZoom(true);
                webView.getSettings().setBuiltInZoomControls(true);
                webView.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);
                webView.setScrollbarFadingEnabled(true);
                webView.getSettings().setLoadsImagesAutomatically(true);
                webView.getSettings().setDomStorageEnabled(true);
                webView.getSettings().setAppCacheEnabled(true);
                // Set cache size to 8 mb by default. should be more than enough
                webView.getSettings().setAppCacheMaxSize(1024*1024*8);
                // This next one is crazy. It's the DEFAULT location for your app's cache
                // But it didn't work for me without this line.
                // UPDATE: no hardcoded path. Thanks to Kevin Hawkins
                String appCachePath = getApplicationContext().getCacheDir().getAbsolutePath();
                Log.e(TAG, "appCachePath = " + appCachePath);
                webView.getSettings().setAppCachePath(appCachePath);
                webView.getSettings().setAllowFileAccess(true);

                webView.getSettings().setJavaScriptEnabled(true);



                // Load the URLs inside the WebView, not in the external web browser
                webView.setWebViewClient(new WebViewClient());  



                webView.getSettings().setCacheMode(WebSettings.LOAD_CACHE_ONLY);

               // webView.loadUrl("http://www.bmimobile.co.uk/", getHeaders());
                webView.loadUrl("http://stackoverflow.com/users/532462/turtleboy");


            }


    }

[EDIT2]

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="uk.bmi.mobile"
        android:versionCode="5"
        android:versionName="1.0.4" >

        <!-- GCM requires Android SDK version 2.2 (API level <img src="http://www.androidhive.info/wp-includes/images/smilies/icon_cool.gif" alt="8)" class="wp-smiley"> or above. -->
        <uses-sdk
            android:minSdkVersion="8"
            android:targetSdkVersion="16" />

        <!-- GCM connects to Internet Services. -->
        <uses-permission android:name="android.permission.INTERNET" />

        <!-- GCM requires a Google account. -->
        <uses-permission android:name="android.permission.GET_ACCOUNTS" />

        <!-- Keeps the processor from sleeping when a message is received. -->
        <uses-permission android:name="android.permission.WAKE_LOCK" />

        <!-- Creates a custom permission so only this app can receive its messages. -->
        <permission
            android:name="uk.bmi.mobile.permission.C2D_MESSAGE"
            android:protectionLevel="signature" />

        <uses-permission android:name="uk.bmi.mobile.permission.C2D_MESSAGE" />

        <!-- This app has permission to register and receive data message. -->
        <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />

        <!-- Network State Permissions to detect Internet status -->
        <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

        <!-- Permission to vibrate -->
        <uses-permission android:name="android.permission.VIBRATE" />

    <uses-permission android:name="android.permisson.ACCESS_WIFI_STATE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

        <!-- Main activity. -->
        <application
            android:icon="@drawable/bmi_icon"
            android:label="@string/app_name"
            android:name="uk.bmi.mobile.ApplicationExt" >
            <!-- Register Activity -->
            <activity
                android:name=".RegisterActivity"
                android:label="@string/app_name" >
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />

                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>

            <!-- Main Activity -->
            <activity
                android:name="uk.bmi.mobile.MainActivity"
                android:configChanges="orientation|keyboardHidden"
                android:label="@string/app_name"
                 android:screenOrientation="portrait" >
            </activity>

            <receiver
                android:name="com.google.android.gcm.GCMBroadcastReceiver"
                android:permission="com.google.android.c2dm.permission.SEND" >
                <intent-filter>

                    <!-- Receives the actual messages. -->
                    <action android:name="com.google.android.c2dm.intent.RECEIVE" />
                    <!-- Receives the registration id. -->
                    <action android:name="com.google.android.c2dm.intent.REGISTRATION" />

                    <category android:name="uk.bmi.mobile" />
                </intent-filter>
            </receiver>

            <service android:name="uk.bmi.mobile.GCMIntentService" />
        </application>

    </manifest>

Answer 1

这不是您问题的确切答案，因为您询问的是webview缓存。但是，它可以达到同样的效果。

// saving page from web to file 
File file = new File(this.getExternalFilesDir(null), "fileName.html");
FileUtils.copyURLToFile(new URL("http://www.bmimobile.co.uk/why-bmi.php"), file);


// loading saved file in webview
webview.loadUrl("file://" + file.getPath());

这是一种更灵活的方法，因为您可以控制加载，保存等等。

Answer 2

也许解决问题的方法是在webview加载的同时发出HTTP get请求。

get请求的结果可以在sharedpreferences中持久存储在字符串中，它将是你的php呈现的HTML。

在您的Android生命周期中，您可以确定应用程序是否处于脱机状态，如果它处于脱机状态，您可以从字符串中加载上次保存的网站版本

webview.loadData(yourSavedString, "text/html", "UTF-8");

虽然如果有图像，您将不得不进行额外的考虑，但如果图像不是动态的，您可以将它们存储在应用程序的资产文件夹中，并将保存的字符串中的URL替换为资产位置。

虽然它无法解决您的webview没有缓存的原因，但它将实现相同的最终目标或离线查看页面

Answer 3

另一个非常灵活且功能强大的选项可以使用HTML5来管理应用中的缓存..

查看http://diveintohtml5.info/offline.html

您只需在应用中启用缓存，然后从网络端自身管理缓存。

最好的问候

Aman Gautam

Answer 4

它的小傻这是有效的。来自

的网址中有重定向

http://www.bmimobile.co.uk/ 至 http://www.bmimobile.co.uk/index.php

你应该试试

webView.loadUrl（＆＃34; http://www.bmimobile.co.uk/why-bmi.php＆＃34 ;, getHeaders（））; webView.loadUrl（＆＃34; http://www.bmimobile.co.uk/index.php＆＃34 ;, getHeaders（））;

Answer 5

有时WebView无法进行本地缓存。如果页眉包含以下字段，则WebView将无法缓存该页面中的内容。

Cache-Control: no-store, no-cache
Pragma: no-cache

在这种情况下，您必须修改服务器上的页面属性以解决缓存问题。

Android WebView无法从缓存中加载第二页

5 个答案: