Android WebViewClient onReceivedError 未因 404 错误而调用

Question

你好
在列表视图中，我有一个 webview，它应该从服务器加载图像文件，当没有图像存在时，我需要一个虚拟图像。我尝试

holder.image.setWebViewClient(new WebViewClient()
{
                  @Override
                public void onReceivedError( WebView view, int errorCode, String description, String failingUrl) 
                {

                    System.out.println("description error" + description);
                    view.setVisibility( View.GONE );

                }

                @Override
                public void onPageFinished(WebView view, String url) {

                    view.setVisibility( View.VISIBLE );


                }


   }); 

在 FrameLayout 中使用这个带有虚拟图像的 webview，onPageFinished 侦听器在每次调用后调用图像 url 已加载，但不会为产生 404 错误的 url 调用 onReceivedError。请猜测如何执行此操作。

Answer 1

我必须重写 WebViewClient.onReceivedHttpError() 而不是 WebViewClient.onReceivedError()。

    @Override
    public void onReceivedHttpError(final WebView view, final WebResourceRequest request, WebResourceResponse errorResponse) {
        final int statusCode;
        // SDK < 21 does not provide statusCode
        if (Build.VERSION.SDK_INT < 21) {
            statusCode = STATUS_CODE_UNKNOWN;
        } else {
            statusCode = errorResponse.getStatusCode();
        }

        Log().d(LOG_TAG, "[onReceivedHttpError]" + statusCode);
    }

来自 WebClient 文档：

/**
 * Notify the host application that an HTTP error has been received from the server while
 * loading a resource.  HTTP errors have status codes >= 400.  This callback will be called
 * for any resource (iframe, image, etc), not just for the main page. Thus, it is recommended to
 * perform minimum required work in this callback. Note that the content of the server
 * response may not be provided within the <b>errorResponse</b> parameter.
 * @param view The WebView that is initiating the callback.
 * @param request The originating request.
 * @param errorResponse Information about the error occured.
 */
public void onReceivedHttpError(
        WebView view, WebResourceRequest request, WebResourceResponse errorResponse) {
}

Answer 2

我今天遇到了同样的问题，

问题：onPageFinished 总是被调用。如果出现错误，它将在 onErrorReceived 之后调用。

这是我找到的解决方案：

holder.image.setWebViewClient(new WebViewClient() {

    private boolean error;

    @Override
    public void onPageStarted(WebView view, String url, Bitmap favicon) {

        super.onPageStarted(view, url, favicon);
        error = false;
    }

    @Override
    public void onReceivedError( WebView view, int errorCode, String description, String failingUrl)  {

        error = true;
        System.out.println("description error" + description);
        view.setVisibility( View.GONE );
    }

    @Override
    public void onPageFinished(WebView view, String url) {

        if (!error) {
            view.setVisibility( View.VISIBLE );
        }
        error = false;
    }

});

Answer 3

@Neeraj 走在正确的轨道上，但我的应用程序允许刷新 Web 视图，因此我需要在加载任何新 URL 之前清除错误状态。此外，错误标志必须作为数据成员存储在父活动上，以便它在 onPageStart() 和 onPageFinish() 期间持续存在——这些方法可以在 onError() 之后调用。

public class MyActivity extends Activity {
    private boolean isError;
    ...
    protected void onResume() {
        super.onResume();
        isError = false;
        myWebView.loadUrl(myUrl);
    }

    public class MyWebViewClient extends WebViewClient {
    /**
     * can be called even after error (embedded images?), so error flag must keep state as data-member in activity, cleared by activity before each loadUrl();          
     */
      @Override
      public void onPageFinished(WebView view, String url) {
        if (!isError)
            showContent();
      }

      @Override
      public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
        isError = true;
        showError();
      }

Answer 4

为了在我的 WebView for API << 中接收主页（而不是资源）的 HTTP 错误， 23，我最终得到了以下解决方案（将其放入您的 WebViewClient 或 WebViewClientCompat 类中）：

@Override
public void onPageFinished(WebView view, String url) {
    if (!WebViewFeature.isFeatureSupported(WebViewFeature.RECEIVE_HTTP_ERROR)) {
        if (view.getTitle().equals("404 Not Found")) {
            // Handle HTTP 404 error here.
        }
        // TODO: Handle more errors, not just 404.
    }
}

因此，我尝试通过查看页面的标题来检测 HTTP 错误。有点hacky，但它适用于我的特定情况（所请求的页面由我自己的服务器托管，因此我可以确定错误页面会是什么样子 - 对于不受您控制的网络服务器，这可能会更困难）。

Answer 5

该代码看起来是正确的；您的页面是否有可能没有生成 404 错误？

Answer 6

holder.image.setWebViewClient(new WebViewClient() { 

    boolean bReceivedError = false;

    @Override
    public void onReceivedError( WebView view, int errorCode,
                                 String description, String failingUrl) { 
      bReceivedError = true;
      view.setVisibility( View.GONE ); 
    }

    @Override 
    public void onPageFinished(WebView view, String url) { 
      if(!bReceivedError)
        view.setVisibility( View.VISIBLE ); 
    } 
  });