如何知道 webView 是否在 android 开始呈现

Question

我正在 WebView 中加载 pdf。

WebView webView = new WebView(this);
webView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setPluginState(WebSettings.PluginState.ON);
webView.setWebViewClient(new WebViewClient());

String url = "http://drive.google.com/viewerng/viewer?embedded=true&url=http://" + getIntent().getStringExtra("url");

webView.loadUrl(url);
setContentView(webView);

每当 activity 启动时，WebView 显示为空白。但我想显示一个进度对话框，直到 WebView 开始呈现 pdf 文件。如何向 WebView 添加一个监听器，表明文件已经开始对用户可见。

Answer 1

您可以创建自定义 class 并使用 WebViewClient 对其进行扩展。然后覆盖方法 onPageStarted ，您可以认为它开始渲染。例如：

private class CustomWebClient extends WebViewClient {

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

      showProgress();

   }
   @Override
   public void onPageFinished(WebView view, String url) {
       super.onPageFinished(view, url);
       dismissDialog();
   }

}

Answer 2

public class FGWebViewClient 扩展 WebViewClient {

private WebViewClient wvc;
private static final String TAG=FGWebViewClient.class.getCanonicalName();
ProgressDialog mProgressDialog;

 // when you add the webviewclient then show the progressDialog.
public FGWebViewClient(Context context) {
    Log.i(TAG, "FGWebViewClient Called...");

   this.wvc=wvc;
    mProgressDialog=new ProgressDialog(context);
    mProgressDialog.setMessage("URL Loading...");
    mProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    mProgressDialog.setCanceledOnTouchOutside(false);


    if(mProgressDialog!=null){
        mProgressDialog.show();
    }



}

@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
Log.i(TAG,"shouldOverrideUrlLoading");
    return  wvc.shouldOverrideUrlLoading(view, url);
}

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

    Log.i(TAG,"onPageStarted");

    wvc.onPageStarted(view, url, favicon);
}
 // OnpageFinished just dismiss the progressDialog.
@Override
public void onPageFinished(WebView view, String url) {

    if(mProgressDialog!=null&&mProgressDialog.isShowing()){
         mProgressDialog.dismiss();
         mProgressDialog=null;
     }

    Log.i(TAG,"onPageFinished");
    //To clear cache of webview
    //view.clearCache(true);
    //clearEveryThing(view);

    wvc.onPageFinished(view,url);
}

然后这样调用

WebView webView=(WebView)v.findViewById(R.id.webView1);

        FGWebViewClient webViewClient=  new FGWebViewClient(context);
        webView.setWebViewClient(webViewClient);


        webView.setWebChromeClient(new WebChromeClient());
        webView.clearCache(true);
        webView.clearHistory();
        webView.getSettings().setJavaScriptEnabled(true);
        webView.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
        webView.loadUrl((webUrl).toString());

Answer 3

您可以使用 setWebViewClient 并显示 showProgress 如下代码

WebSettings settings = webView.getSettings();
            settings.setJavaScriptEnabled(true);
            settings.setPluginState(WebSettings.PluginState.ON);
            webView.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);

            showProgress();
            webView.setWebViewClient(new WebViewClient() {
                public boolean shouldOverrideUrlLoading(WebView view, String url) {
                    view.loadUrl(url);
                    return true;
                }

                public void onPageFinished(WebView view, String url) {
                    hideProgress();
                }

                public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
                    hideProgress();
                }

            });

String url = "http://drive.google.com/viewerng/viewer?embedded=true&url=http://" + getIntent().getStringExtra("url");

webView.loadUrl(url);

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