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Android webveiw 出现栈错误解决办法

2019年07月24日  | 移动技术网IT编程  | 我要评论

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android webveiw 出现栈错误解决办法

前言：

最近做一个项目，项目调试基础库的一个调试工具展示设备信息页面使用webview。有一个应用集成调试基础库展示内容时出现

java.lang.unsupportedoperationexception: for security reasons, webview is not allowed in privileged processes

因为应用是系统级别的，在androidmanifest.xml中添加了android:shareduserid="android.uid.system"

根据exception提示出于安全原因，所以初步断定很可能跟应用为系统应用有很大关系，于是开始了查找代码寻源之旅

首先我们看一下具体的错误堆栈

at android.app.activitythread.performlaunchactivity(activitythread.java:2325) 
at android.app.activitythread.handlelaunchactivity(activitythread.java:2387) 
at android.app.activitythread.access$800(activitythread.java:151) 
at android.app.activitythread$h.handlemessage(activitythread.java:1303) 
at android.os.handler.dispatchmessage(handler.java:102) 
at android.os.looper.loop(looper.java:135) 
at android.app.activitythread.main(activitythread.java:5257) 
at java.lang.reflect.method.invoke(native method) 
at java.lang.reflect.method.invoke(method.java:372) 
at com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:955) 
at com.android.internal.os.zygoteinit.main(zygoteinit.java:750) 
aused by: android.view.inflateexception: binary xml file line #17: error inflating class android.webkit.webview 
at android.view.layoutinflater.createview(layoutinflater.java:633) 
at com.android.internal.policy.impl.phonelayoutinflater.oncreateview(phonelayoutinflater.java:55) 
at android.view.layoutinflater.oncreateview(layoutinflater.java:682) 
at android.view.layoutinflater.createviewfromtag(layoutinflater.java:741) 
at android.view.layoutinflater.rinflate(layoutinflater.java:806) 
at android.view.layoutinflater.inflate(layoutinflater.java:504) 
at android.view.layoutinflater.inflate(layoutinflater.java:414) 
at android.view.layoutinflater.inflate(layoutinflater.java:365) 
at com.android.internal.policy.impl.phonewindow.setcontentview(phonewindow.java:379) 
at android.app.activity.setcontentview(activity.java:2145) 
at com.mipt.store.activity.infoactivity.oncreate(unknown source) 
at android.app.activity.performcreate(activity.java:5990) 
at android.app.instrumentation.callactivityoncreate(instrumentation.java:1106) 
at android.app.activitythread.performlaunchactivity(activitythread.java:2278) 
... 10 more 
aused by: java.lang.reflect.invocationtargetexception 
at java.lang.reflect.constructor.newinstance(native method) 
at java.lang.reflect.constructor.newinstance(constructor.java:288) 
at android.view.layoutinflater.createview(layoutinflater.java:607) 
... 23 more 
aused by: java.lang.unsupportedoperationexception: for security reasons, webview is not allowed in privileged processes 
at android.webkit.webviewfactory.getprovider(webviewfactory.java:96) 
at android.webkit.webview.getfactory(webview.java:2194) 
at android.webkit.webview.ensureprovidercreated(webview.java:2189) 
at android.webkit.webview.setoverscrollmode(webview.java:2248) 
at android.view.view.<init>(view.java:3588) 
at android.view.view.<init>(view.java:3682) 
at android.view.viewgroup.<init>(viewgroup.java:497) 
at android.widget.absolutelayout.<init>(absolutelayout.java:55) 
at android.webkit.webview.<init>(webview.java:544) 
at android.webkit.webview.<init>(webview.java:489) 
at android.webkit.webview.<init>(webview.java:472) 
at android.webkit.webview.<init>(webview.java:459) 
... 26 more

错误提示显示为“caused by: java.lang.unsupportedoperationexception: for security reasons, webview is not allowed in privileged processes”

security reasons即安全原因。为了查明原因直接查看android源码。经过一番查找，发现抛出exception的在

frameworks/base/master/core/java/android/webkit/webviewfactory.java

static webviewfactoryprovider getprovider() { 
 synchronized (sproviderlock) { 
  // for now the main purpose of this function (and the factory abstraction) is to keep 
  // us honest and minimize usage of webview internals when binding the proxy. 
  if (sproviderinstance != null) return sproviderinstance; 
  final int uid = android.os.process.myuid(); 
  if (uid == android.os.process.root_uid || uid == android.os.process.system_uid) { 
   throw new unsupportedoperationexception( 
     "for security reasons, webview is not allowed in privileged processes"); 
  } 
  strictmode.threadpolicy oldpolicy = strictmode.allowthreaddiskreads(); 
  trace.tracebegin(trace.trace_tag_webview, "webviewfactory.getprovider()"); 
  try { 
   class<webviewfactoryprovider> providerclass = getproviderclass(); 
   trace.tracebegin(trace.trace_tag_webview, "providerclass.newinstance()"); 
   try { 
    sproviderinstance = providerclass.getconstructor(webviewdelegate.class) 
      .newinstance(new webviewdelegate()); 
    if (debug) log.v(logtag, "loaded provider: " + sproviderinstance); 
    return sproviderinstance; 
   } catch (exception e) { 
    log.e(logtag, "error instantiating provider", e); 
    throw new androidruntimeexception(e); 
   } finally { 
    trace.traceend(trace.trace_tag_webview); 
   } 
  } finally { 
   trace.traceend(trace.trace_tag_webview); 
   strictmode.setthreadpolicy(oldpolicy); 
  } 
 } 
}

webview在初始化的时候会检查初始化进程的id.

final int uid = android.os.process.myuid(); 
if (uid == android.os.process.root_uid || uid == android.os.process.system_uid) { 
 throw new unsupportedoperationexception( 
  "for security reasons, webview is not allowed in privileged processes"); 
}

如果进程id是root或者system，就会抛出unsupportedoperationexception。为什么会有这种安全机制呢？因为webview允许运行js，如果用户通过js注入安全代码，那么js就可以肆无忌惮的使用系统权限，这无疑是一个漏洞，可谓门户大开。

果不其然就是android:shareduserid="android.uid.system"的问题，因为是系统应用所以只能修改基础调试库的展示控件，把展示调试信息的webview改为textview。

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