在少数地方可以处理此问题。
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.encodeToString(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);
}
});
}
}
}
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