问题描述：
因公司业务需要，现在 Android 存在的方式基本都是原生与 h5 页面共存的情况。近日发现，当应用中存在多个 WebView 实例去渲染 h5 页面的时候，就有可能会出现程序异常崩溃的情况，在低端机中表现较为明显。
出现的原因：
通过日志排查发现，在 log 控制台除了打印一堆 dump 日志之外，还有一行格外鲜艳的话：
Render process (11786)'s crash wasn't handled by all associated webviews, triggering application crash.
这句话大致的意思就是，由于相关联的所有 WebView 没有处理渲染进程的 crash，进而触发了我们 application 的 crash。
查阅官方文档，发现 WebViewClient 中有一个回调方法 onRenderProcessGone
/**
* Notify host application that the given WebView's render process has exited.
*
* Multiple WebView instances may be associated with a single render process;
* onRenderProcessGone will be called for each WebView that was affected.
* The application's implementation of this callback should only attempt to
* clean up the specific WebView given as a parameter, and should not assume
* that other WebView instances are affected.
*
* The given WebView can't be used, and should be removed from the view hierarchy,
* all references to it should be cleaned up, e.g any references in the Activity
* or other classes saved using {@link android.view.View#findViewById} and similar calls, etc.
*
* To cause an render process crash for test purpose, the application can
* call {@code loadUrl("chrome://crash")} on the WebView. Note that multiple WebView
* instances may be affected if they share a render process, not just the
* specific WebView which loaded chrome://crash.
*
* @param view The WebView which needs to be cleaned up.
* @param detail the reason why it exited.
* @return {@code true} if the host application handled the situation that process has
* exited, otherwise, application will crash if render process crashed,
* or be killed if render process was killed by the system.
*/
public boolean onRenderProcessGone(WebView view, RenderProcessGoneDetail detail) {
return false;
}
从官方的注释中可以看到，当WebView 的 Render Process 被移除的时候就会回调该方法，再继续跟到里面看具体的实现，我这用的调试机是荣耀的，所以这里的实现是一个SaveWebView 的类。
@SuppressLint({"NewApi"})
public boolean onRenderProcessGone(WebView var1, RenderProcessGoneDetail var2) {
return this.O != null ? this.O.onRenderProcessGone(var1, var2) : super.onRenderProcessGone(var1, var2);
}
一目了然，这里的 O 就是 WebViewClient，当 WebViewClient 不为空的时候就会调用进来。
再回到上一步，发现 onRenderProcessGone 是虚类 WebViewRenderProcess 里面的一个方法。
/**
* WebViewRenderProcess provides an opaque handle to a {@link WebView} renderer.
*/
public abstract class WebViewRenderProcess {
/**
* Cause this renderer to terminate.
*
* <p>Calling this on a not yet started, or an already terminated renderer will have no effect.
*
* <p>Terminating a renderer process may have an effect on multiple {@link WebView} instances.
*
* <p>Renderer termination must be handled by properly overriding
* {@link WebViewClient#onRenderProcessGone} for every WebView that shares this
* renderer. If termination is not handled by all associated WebViews, then the application
* process will also be terminated.
*
* @return {@code true} if it was possible to terminate this renderer, {@code false} otherwise.
*/
public abstract boolean terminate();
public WebViewRenderProcess() {
}
}
再看看这个类在哪有引用到，接着继续往下跟发现在 WebViewRenderProcessClient 里面有个 onRenderProcessUnresponsive 方法。
关于 WebViewRenderProcessClient 有这么一段注释：
/**
* Used to receive callbacks on {@link WebView} renderer events.
*
* WebViewRenderProcessClient instances may be set or retrieved via {@link
* WebView#setWebViewRenderProcessClient(WebViewRenderProcessClient)} and {@link
* WebView#getWebViewRenderProcessClient()}.
*
* Instances may be attached to multiple WebViews, and thus a single renderer event may cause
* a callback to be called multiple times with different WebView parameters.
*/
大致意思就是说，这个类会接收 render 进程的事件回调，然后做一些判断处理，回调相应抑或是不响应。
/**
* Called when the renderer currently associated with {@code view} becomes unresponsive as a
* result of a long running blocking task such as the execution of JavaScript.
*
* <p>If a WebView fails to process an input event, or successfully navigate to a new URL within
* a reasonable time frame, the renderer is considered to be unresponsive, and this callback
* will be called.
*
* <p>This callback will continue to be called at regular intervals as long as the renderer
* remains unresponsive. If the renderer becomes responsive again, {@link
* WebViewRenderProcessClient#onRenderProcessResponsive} will be called once, and this method
* will not subsequently be called unless another period of unresponsiveness is detected.
*
* <p>The minimum interval between successive calls to {@code onRenderProcessUnresponsive} is 5
* seconds.
*
* <p>No action is taken by WebView as a result of this method call. Applications may
* choose to terminate the associated renderer via the object that is passed to this callback,
* if in multiprocess mode, however this must be accompanied by correctly handling
* {@link WebViewClient#onRenderProcessGone} for this WebView, and all other WebViews associated
* with the same renderer. Failure to do so will result in application termination.
*
* @param view The {@link WebView} for which unresponsiveness was detected.
* @param renderer The {@link WebViewRenderProcess} that has become unresponsive,
* or {@code null} if WebView is running in single process mode.
*/
public abstract void onRenderProcessUnresponsive(
@NonNull WebView view, @Nullable WebViewRenderProcess renderer);
从注释中我们可以看到，当 Render 进程长时间无响应的时候，就会触发这个方法。比如因为 JavaScript 长时间无响应、输入相应事件长时间无响应抑或是导航至新的 url 无响应等。
到这里，基本就比较明晰了。也就是说，当 WebView 的任务过重，如 JavaScrip 长时间无响应，抑或是其他导致响应事件过长的情况，都有可能会触发 render 进程移除，如果不加以处理，就会导致我们的应用进程被强制停止。
解决办法：
既然当系统 WebView 的 Render 进程被移除时会给到我们相应的回调，因此我们直接重写 onRenderProcessGone 方法。
simple代码大致如下，根据实际业务进行处理，仅供参考。
@Override
public boolean onRenderProcessGone(WebView view, RenderProcessGoneDetail detail) {
if (Build.VERSION.SDK_INT > Build.VERSION_CODES.O) {
return false;
}
// 仅对我们自己的 webview 做处理
if ( view == mWebView) {
// 获取 webview 所在父布局
ViewGroup parent = (ViewGroup) mWebView.getParent();
ViewGroup.LayoutParams params = mWebView.getLayoutParams();
// 把无效不可用的 webview 从布局中移除
destroyWebView();
// 重新创建新的 webview
WebView newWebView = new WebView(getActivity());
newWebView.setId(R.id.webView);
parent.addView(newWebView, 0, params);
Bundle bundle = getArguments();
// 重走初始化流程，渲染 UI，加载 url
initView(root);
return true;
}
return super.onRenderProcessGone(view, detail);
}
以上。
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