問題描述：

因公司業(yè)務需要，現(xiàn)在 Android 存在的方式基本都是原生與 h5 頁面共存的情況。近日發(fā)現(xiàn)，當應用中存在多個 WebView 實例去渲染 h5 頁面的時候，就有可能會出現(xiàn)程序異常崩潰的情況，在低端機中表現(xiàn)較為明顯。

出現(xiàn)的原因：

通過日志排查發(fā)現(xiàn)，在 log 控制臺除了打印一堆 dump 日志之外，還有一行格外鮮艷的話：

Render process (11786)'s crash wasn't handled by all associated webviews, triggering application crash.

這句話大致的意思就是，由于相關聯(lián)的所有 WebView 沒有處理渲染進程的 crash，進而觸發(fā)了我們 application 的 crash。
查閱官方文檔，發(fā)現(xiàn) WebViewClient 中有一個回調(diào)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;
    }

從官方的注釋中可以看到，當WebView 的 Render Process 被移除的時候就會回調(diào)該方法，再繼續(xù)跟到里面看具體的實現(xiàn)，我這用的調(diào)試機是榮耀的，所以這里的實現(xiàn)是一個SaveWebView 的類。

        @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，這里的 O 就是 WebViewClient，當 WebViewClient 不為空的時候就會調(diào)用進來。
再回到上一步，發(fā)現(xiàn) onRenderProcessGone 是虛類 WebViewRenderProcess 里面的一個方法。

/**
 * 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() {
    }
}

再看看這個類在哪有引用到，接著繼續(xù)往下跟發(fā)現(xiàn)在 WebViewRenderProcessClient 里面有個 onRenderProcessUnresponsive 方法。
關于 WebViewRenderProcessClient 有這么一段注釋：

/**
 * 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.
 */

大致意思就是說，這個類會接收 render 進程的事件回調(diào)，然后做一些判斷處理，回調(diào)相應抑或是不響應。

    /**
     * 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);

從注釋中我們可以看到，當 Render 進程長時間無響應的時候，就會觸發(fā)這個方法。比如因為 JavaScript 長時間無響應、輸入相應事件長時間無響應抑或是導航至新的 url 無響應等。
到這里，基本就比較明晰了。也就是說，當 WebView 的任務過重，如 JavaScrip 長時間無響應，抑或是其他導致響應事件過長的情況，都有可能會觸發(fā) render 進程移除，如果不加以處理，就會導致我們的應用進程被強制停止。

解決辦法：

既然當系統(tǒng) WebView 的 Render 進程被移除時會給到我們相應的回調(diào)，因此我們直接重寫 onRenderProcessGone 方法。
simple代碼大致如下，根據(jù)實際業(yè)務進行處理，僅供參考。

            @Override
            public boolean onRenderProcessGone(WebView view, RenderProcessGoneDetail detail) {
                if (Build.VERSION.SDK_INT > Build.VERSION_CODES.O) {
                    return false;
                }
                // 僅對我們自己的 webview 做處理
                if ( view == mWebView) {
                  // 獲取 webview 所在父布局
                    ViewGroup parent = (ViewGroup) mWebView.getParent();
                    ViewGroup.LayoutParams params = mWebView.getLayoutParams();
                    // 把無效不可用的 webview 從布局中移除
                    destroyWebView();
                   // 重新創(chuàng)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，加載 url
                    initView(root);
                    return true;
                }
                return super.onRenderProcessGone(view, detail);
            }

以上。