Android：我如何知道CSS注入已完成？

在少数地方可以处理此问题。

• 您可以使用

  evaluateJavascript

  代替

  loadUrl

  （API级别19）并传递回调，在该回调中将Webview设置为可见。
• 您可以使用注册自己的javascript接口，

  addJavascriptInterface

  并在脚本结尾处调用它
• 您可以设置

  WebChromeClient

  并覆盖，

  onJsalert

  然后在脚本中使用特定消息引发警报。
• 更新 ：此外，这可以通过拦截“ css”请求之一，并在加载的文件中附加所需的内容来实现。这将使您可以在之前插入样式

  onPageFinished

  。检查此线程。

在以下示例中，我结合了所有方法：

    package com.j2ko.webviewapp;    import android.support.v7.app.AppCompatActivity;    import android.os.Bundle;    import android.util.base64;    import android.util.Log;    import android.view.View;    import android.webkit.JavascriptInterface;    import android.webkit.JsResult;    import android.webkit.ValueCallback;    import android.webkit.WebChromeClient;    import android.webkit.WebView;    import android.webkit.WebViewClient;    import java.io.InputStream;    import java.io.StringReader;    import java.io.StringWriter;    public class MainActivity extends AppCompatActivity {        private static final String MAIN_FUNC_FMT = "(function() { %s })()";        private static final String FUNC_BODY_FMT =     "var parent = document.loadedgetElementsByTagName('head').item(0);" +  "var css = document.createElement('style');" +  "css.type = 'text/css';" +  "css.innerHTML = %s;" +  "parent.appendChild(css);";        private static final String base64_DECODE_FMT = "window.atob('%s')";        WebView mWebView;        @Override        protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mWebView = (WebView) findViewById(R.id.webview); mWebView.getSettings().setJavascriptEnabled(true); mWebView.setWebViewClient(new WebViewClient() {     @Override     public void onPageFinished(WebView view, String url) {         super.onPageFinished(view, url);         //Change it to whatever         injectWithevaluateAndInterface(view);     }     @Override     public void onLoadResource(WebView view, String url) {         super.onLoadResource(view, url);     } }); mWebView.setVisibility(View.INVISIBLE); mWebView.loadUrl("http://wiki.org");        }        private static class CSSInjectBuilder { private final String mOrigin; private String mAtEnd = null; private boolean mUsebase64 = false; public CSSInjectBuilder(String css) {     mOrigin = css; } public CSSInjectBuilder withbase64() {     mUsebase64 = true;     return this; } public CSSInjectBuilder withexpressionAtEnd(String expression){     mAtEnd = expression;     return this; } String build() {     String func_body = FUNC_BODY_FMT;     if (mAtEnd != null) {         func_body += mAtEnd;     }     final String css;     if (mUsebase64) {         byte[] buffer = mOrigin.getBytes();         css = String.format(base64_DECODE_FMT, base64.enpreToString(buffer, base64.NO_WRAP));     } else {         css = "'" + mOrigin + "'";     }     func_body = String.format(func_body, css);     return String.format(MAIN_FUNC_FMT, func_body); }        }        byte[] loadAsset() { try {     InputStream inputStream = getAssets().open("style.css");     byte[] buffer = new byte[inputStream.available()];     inputStream.read(buffer);     inputStream.close();     return buffer; } catch (Exception e) { } return null;        }        String loadCSS() { return new String(loadAsset());        }        void injectWithevaluate(final WebView view) { view.evaluateJavascript(new CSSInjectBuilder(loadCSS()).withbase64().build(), new ValueCallback<String>() {     @Override     public void onReceivevalue(String value) {         view.setVisibility(View.VISIBLE);     } });        }        void injectWithevaluateAndInterface(WebView view) { view.addJavascriptInterface(new WebViewInterface(), "WebViewBackEnd"); final String injector = new CSSInjectBuilder(loadCSS())         .withbase64()         .withexpressionAtEnd("window.WebViewBackEnd.CSSInjectionComplete();")         .build(); view.evaluateJavascript(injector, null);        }        void injectWithLoadUrlSimple(WebView view) { view.loadUrl("javascript:" + loadCSS()); view.setVisibility(View.VISIBLE);        }        void injectWithLoadUrlAndCheckalert(final WebView view) { view.setWebChromeClient(new WebChromeClient() {     @Override     public boolean onJsalert(WebView view, String url, String message, JsResult result) {         if (message.equals("CSSInjectionComplete")) {  view.setVisibility(View.VISIBLE);  return true;         }         return super.onJsalert(view, url, message, result);     } }); //alert could hang aplying scripts so put it on timeout final String injector = new CSSInjectBuilder(loadCSS())         .withbase64()         .withexpressionAtEnd("setTimeout(function(){alert('CSSInjectionComplete');}, 1);")         .build(); view.loadUrl("javascript:"  + injector);        }        private class WebViewInterface { @JavascriptInterface public void CSSInjectionComplete(){     mWebView.post(new Runnable() {         @Override         public void run() {  mWebView.setVisibility(View.VISIBLE);         }     }); }        }    }