记录 Android WebView 开发过程的坑和解决方法

这篇主要总结 WebView 相关的疑难 bug，由于 Android 版本严重碎片化，在使用 WebView 的时候也会遇到各种个样的坑，特别是 4.4 之后更换了 WebView 内核，4.2 以下有部分漏洞，所以想把经历过的 WebView 这些坑记录下来，仅供参考。

1、

java.lang.NullPointerException
    at android.webkit.AccessibilityInjector$TextToSpeechWrapper$1.onInit(AccessibilityInjector.java:753)
    at android.speech.tts.TextToSpeech.dispatchOnInit(TextToSpeech.java:640)
    at android.speech.tts.TextToSpeech.initTts(TextToSpeech.java:619)
    at android.speech.tts.TextToSpeech.<init>(TextToSpeech.java:553)
    at android.webkit.AccessibilityInjector$TextToSpeechWrapper.<init>(AccessibilityInjector.java:676)
    at android.webkit.AccessibilityInjector.addTtsApis(AccessibilityInjector.java:480)
    at android.webkit.AccessibilityInjector.addAccessibilityApisIfNecessary(AccessibilityInjector.java:168)
    at android.webkit.AccessibilityInjector.onPageStarted(AccessibilityInjector.java:340)
    at android.webkit.WebViewClassic.onPageStarted(WebViewClassic.java:4480)
    at android.webkit.CallbackProxy.handleMessage(CallbackProxy.java:366)
    at android.os.Handler.dispatchMessage(Handler.java:107)
    at android.os.Looper.loop(Looper.java:194)
    at android.app.ActivityThread.main(ActivityThread.java:5407)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:525)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
    at dalvik.system.NativeStart.main(Native Method)

此问题在4.2.1和4.2.2比较集中，关闭辅助功能，google 下很多结果都是一样的。

修复方法：在初始化 WebView 时调用disableAccessibility方法即可。

public static void disableAccessibility(Context context) {
        if (Build.VERSION.SDK_INT == 17/*4.2 (Build.VERSION_CODES.JELLY_BEAN_MR1)*/) {
            if (context != null) {
                try {
                    AccessibilityManager am = (AccessibilityManager) context.getSystemService(Context.ACCESSIBILITY_SERVICE);
                    if (!am.isEnabled()) {
                        //Not need to disable accessibility
                        return;
                    }

                    Method setState = am.getClass().getDeclaredMethod("setState", int.class);
                    setState.setAccessible(true);
                    setState.invoke(am, 0);/**{@link AccessibilityManager#STATE_FLAG_ACCESSIBILITY_ENABLED}*/
                } catch (Exception ignored) {
                    ignored.printStackTrace();
                }
            }
        }
    }

2、

AndroidRuntimeException: android.content.pm.PackageManager$NameNotFoundException: com.google.android.webview
    at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4604)
    at android.app.ActivityThread.access$1500(ActivityThread.java:154)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1389)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5302)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:916)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:711)
Caused by: android.util.AndroidRuntimeException: android.content.pm.PackageManager$NameNotFoundException: com.google.android.webview
    at android.webkit.WebViewFactory.getFactoryClass(WebViewFactory.java:174)
    at android.webkit.WebViewFactory.getProvider(WebViewFactory.java:109)
    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)
    at android.webkit.WebView.<init>(WebView.java:449)

现象：在创建 WebView 时崩溃，跟进栈信息，我们需要在 setOverScrollMode 方法上加异常保护处理

修复方法：

try {
    super.setOverScrollMode(mode);
} catch (Throwable e) {
    e.printStackTrace();
}  

不过上面捕获的异常范围有点广，在github上找到一个更全面的修复方法

try{
    super.setOverScrollMode(mode);
} catch(Throwable e){
        String messageCause = e.getCause() == null ? e.toString() : e.getCause().toString();
String trace = Log.getStackTraceString(e);
if (trace.contains("android.content.pm.PackageManager$NameNotFoundException")
  || trace.contains("java.lang.RuntimeException: Cannot load WebView")
    || trace.contains("android.webkit.WebViewFactory$MissingWebViewPackageException: Failed to load WebView provider: No WebView installed")) {
      e.printStackTrace();
    }else{
      throw e;
    }        
}

3、

at android.webkit.BrowserFrame.nativeLoadUrl(Native Method)
System.err:     at android.webkit.BrowserFrame.loadUrl(BrowserFrame.java:279)
System.err:     at android.webkit.WebViewCore.loadUrl(WebViewCore.java:2011)
System.err:     at android.webkit.WebViewCore.access$1900(WebViewCore.java:57)
System.err:     at android.webkit.WebViewCore$EventHub$1.handleMessage(WebViewCore.java:1303)
System.err:     at android.os.Handler.dispatchMessage(Handler.java:99)
System.err:     at android.os.Looper.loop(Looper.java:137)
System.err:     at android.webkit.WebViewCore$WebCoreThread.run(WebViewCore.java:812)
System.err:     at java.lang.Thread.run(Thread.java:856)
webcoreglue: *** Uncaught exception returned from Java call!
System.err: java.lang.NullPointerException
System.err:     at android.webkit.WebViewClassic.clearView(WebViewClassic.java:2868)
System.err:     at android.webkit.WebViewCore.setupViewport(WebViewCore.java:2497)
System.err:     at android.webkit.WebViewCore.updateViewport(WebViewCore.java:2479)
System.err:     at android.webkit.BrowserFrame.nativeLoadUrl(Native Method)
System.err:     at android.webkit.BrowserFrame.loadUrl(BrowserFrame.java:279)
System.err:     at android.webkit.WebViewCore.loadUrl(WebViewCore.java:2011)
System.err:     at android.webkit.WebViewCore.access$1900(WebViewCore.java:57)
System.err:     at android.webkit.WebViewCore$EventHub$1.handleMessage(WebViewCore.java:1303)
System.err:     at android.os.Handler.dispatchMessage(Handler.java:99)
System.err:     at android.os.Looper.loop(Looper.java:137)

这个bug是在某些设备上发生的，是在调用webView.destroy() 之前调用了loadurl操作发生的，也不是毕现问题，所以只能跟进源码查看，
在清空 webview destroy 时，调用清理方法，内部可能时机有问题，会出现，WebViewClassic 中 mWebViewCore 对象为null，其内部为handler消息机制。

修复方法：

public void logdUrl(final String url) {
    try {
        super.loadUrl(url);
    } catch (NullPointerException e) {
        e.printStackTrace();
    }
}