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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.webkit;
     18 
     19 import android.os.Build;
     20 import android.os.StrictMode;
     21 import android.os.SystemProperties;
     22 import android.util.Log;
     23 
     24 import dalvik.system.PathClassLoader;
     25 
     26 /**
     27  * Top level factory, used creating all the main WebView implementation classes.
     28  */
     29 class WebViewFactory {
     30     // Default Provider factory class name.
     31     // TODO: When the Chromium powered WebView is ready, it should be the default factory class.
     32     private static final String DEFAULT_WEBVIEW_FACTORY = "android.webkit.WebViewClassic$Factory";
     33     private static final String CHROMIUM_WEBVIEW_FACTORY =
     34             "com.android.webviewchromium.WebViewChromiumFactoryProvider";
     35     private static final String CHROMIUM_WEBVIEW_JAR = "/system/framework/webviewchromium.jar";
     36 
     37     private static final String LOGTAG = "WebViewFactory";
     38 
     39     private static final boolean DEBUG = false;
     40 
     41     // Cache the factory both for efficiency, and ensure any one process gets all webviews from the
     42     // same provider.
     43     private static WebViewFactoryProvider sProviderInstance;
     44     private static final Object sProviderLock = new Object();
     45 
     46     static WebViewFactoryProvider getProvider() {
     47         synchronized (sProviderLock) {
     48             // For now the main purpose of this function (and the factory abstraction) is to keep
     49             // us honest and minimize usage of WebViewClassic internals when binding the proxy.
     50             if (sProviderInstance != null) return sProviderInstance;
     51 
     52             // For debug builds, we allow a system property to specify that we should use the
     53             // Chromium powered WebView. This enables us to switch between implementations
     54             // at runtime. For user (release) builds, don't allow this.
     55             if (Build.IS_DEBUGGABLE && SystemProperties.getBoolean("webview.use_chromium", false)) {
     56                 StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
     57                 try {
     58                     sProviderInstance = loadChromiumProvider();
     59                     if (DEBUG) Log.v(LOGTAG, "Loaded Chromium provider: " + sProviderInstance);
     60                 } finally {
     61                     StrictMode.setThreadPolicy(oldPolicy);
     62                 }
     63             }
     64 
     65             if (sProviderInstance == null) {
     66                 if (DEBUG) Log.v(LOGTAG, "Falling back to default provider: "
     67                         + DEFAULT_WEBVIEW_FACTORY);
     68                 sProviderInstance = getFactoryByName(DEFAULT_WEBVIEW_FACTORY,
     69                         WebViewFactory.class.getClassLoader());
     70                 if (sProviderInstance == null) {
     71                     if (DEBUG) Log.v(LOGTAG, "Falling back to explicit linkage");
     72                     sProviderInstance = new WebViewClassic.Factory();
     73                 }
     74             }
     75             return sProviderInstance;
     76         }
     77     }
     78 
     79     // TODO: This allows us to have the legacy and Chromium WebView coexist for development
     80     // and side-by-side testing. After transition, remove this when no longer required.
     81     private static WebViewFactoryProvider loadChromiumProvider() {
     82         ClassLoader clazzLoader = new PathClassLoader(CHROMIUM_WEBVIEW_JAR, null,
     83                 WebViewFactory.class.getClassLoader());
     84         return getFactoryByName(CHROMIUM_WEBVIEW_FACTORY, clazzLoader);
     85     }
     86 
     87     private static WebViewFactoryProvider getFactoryByName(String providerName,
     88             ClassLoader loader) {
     89         try {
     90             if (DEBUG) Log.v(LOGTAG, "attempt to load class " + providerName);
     91             Class<?> c = Class.forName(providerName, true, loader);
     92             if (DEBUG) Log.v(LOGTAG, "instantiating factory");
     93             return (WebViewFactoryProvider) c.newInstance();
     94         } catch (ClassNotFoundException e) {
     95             Log.e(LOGTAG, "error loading " + providerName, e);
     96         } catch (IllegalAccessException e) {
     97             Log.e(LOGTAG, "error loading " + providerName, e);
     98         } catch (InstantiationException e) {
     99             Log.e(LOGTAG, "error loading " + providerName, e);
    100         }
    101         return null;
    102     }
    103 }
    104