我有一个仅包含网站的Android应用程序。我希望该应用程序缓存网站页面以供离线使用。
我正在进行简单的测试,以查看缓存是否有效,但不幸的是,在离线模式下无法加载之前在线加载过的页面。为了让事情更清楚,我在在线模式下加载以下两个页面。
我希望“why-bmi.php”页面以及随后的页面http://www.bmimobile.co.uk/能够被缓存。后者页面有一个链接指向第一个页面。如果我退出应用程序并关闭网络适配器,然后重新进入应用程序,“http://www.bmimobile.co.uk/”页面会显示,但是当我点击“why-bmi”链接时,该页面不会显示,只会出现一个短暂的提示信息“加载页面错误”。请问有谁知道为什么Webview没有将已加载的页面缓存起来以供离线使用?以下是主要活动内容,我还扩展了应用程序对象以定义appcachepath。提前感谢您的帮助。Matt
我正在进行简单的测试,以查看缓存是否有效,但不幸的是,在离线模式下无法加载之前在线加载过的页面。为了让事情更清楚,我在在线模式下加载以下两个页面。
webView.loadUrl("http://www.bmimobile.co.uk/why-bmi.php", getHeaders());
webView.loadUrl("http://www.bmimobile.co.uk/", getHeaders());
我希望“why-bmi.php”页面以及随后的页面http://www.bmimobile.co.uk/能够被缓存。后者页面有一个链接指向第一个页面。如果我退出应用程序并关闭网络适配器,然后重新进入应用程序,“http://www.bmimobile.co.uk/”页面会显示,但是当我点击“why-bmi”链接时,该页面不会显示,只会出现一个短暂的提示信息“加载页面错误”。请问有谁知道为什么Webview没有将已加载的页面缓存起来以供离线使用?以下是主要活动内容,我还扩展了应用程序对象以定义appcachepath。提前感谢您的帮助。Matt
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();
}
}
}
这是应用程序在在线模式下首次加载时的日志记录
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
当我退出应用程序,关闭网络适配器,然后以离线模式重新进入应用程序时,这是记录日志的内容。
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
[编辑1] 实际上,仔细检查日志后发现,在在线模式下加载时已经发生了变化。以下是在线模式下的日志记录。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] 如果我在在线模式下点击“为什么要计算BMI”按钮,然后退出应用程序,关闭适配器,再次点击“为什么要计算BMI”按钮,则会显示“加载页面时出错”的消息。
然而,如果我更改为以下网址,则会显示我的SO页面。如果我单击链接到我的赏金页面(此页面),然后离线,SO页面会像您所期望的那样显示,但是如果您在离线模式下单击赏金链接,则确实会显示。因此,SO网站和BMI网站之间存在差异。
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>