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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