在项目中遇到JQuery注入后，执行无效的问题。

我们知道必须在网页加载完成后，也就是在onPageFinished()方法被调用后才能执行被注入的JS。

但是在有些手机上并不能成功执行，我的解决方案是设置一秒延迟后注入JS，成功了！why，i dont know...

WebView注入JS的封装

JSUtil.java

import android.app.Activity;

import android.webkit.ValueCallback;

import android.webkit.WebView;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

public class JSUtil {

public static JSUtil instance;

private WebView webview;

private String juqueryContent;

public static JSUtil getInstance(WebView webView) {

if (instance == null) {

instance = new JSUtil(webView);

} else {

instance.webview = webView;

}

return instance;

}

private JSUtil(WebView webView) {

webview = webView;

try {

InputStream in = webView.getContext().getAssets().open("jquery.min.js");

byte buff[] = new byte[1024];

ByteArrayOutputStream fromFile = new ByteArrayOutputStream();

do {

int numread = in.read(buff);

if (numread <= 0) {

break;

}

fromFile.write(buff, 0, numread);

} while (true);

juqueryContent = fromFile.toString();

} catch (IOException e) {

e.printStackTrace();

}

}

/**

* 注入jquery

*/

public void injectJquery(final InjectCallback injectCallback) {

webview.loadUrl("javascript:" + juqueryContent);

webview.postDelayed(new Runnable() {

@Override

public void run() {

injectCallback.onSuccess();

}

},1000);

}

interface InjectCallback {

void onSuccess();

void onFail();

}

/**

* 原生设置dom值

*/

public void js_dom_setValueById(String id, String value) {

String js = "javascript:document.getElementById('" + id + "').value = '" + value + "'";

loadJs(js);

}

/**

* 原生设置dom值

*/

public void js_dom_setValueByName(String name, String value) {

String js = "javascript:document.getElementsByName('" + name + "').value = '" + value + "'";

loadJs(js);

}

/**

* js原生dom点击(通过id查找)

*/

public void js_dom_click_byId(String id) {

String js = "javascript:document.getElementById('" + id + "').click();";

webview.evaluateJavascript(js, null);

}

/**

* js原生dom点击(通过类查找)

*/

public void js_dom_click_byClass(String cls) {

String js = "javascript:document.getElementsByClassName('" + cls + "').click();";

webview.evaluateJavascript(js, null);

}

/**

* jquerydom点击(通过id查找)

*/

public void jquery_dom_click_byId(String id) {

String js = "var newscript = document.createElement(\"script\");";

js += "newscript.src=\"https://cdn.bootcss.com/jquery/1.12.4/jquery.min.js\";";

js += "document.body.appendChild(newscript);";

js += "newscript.οnlοad=function(){$('#" + id + "').click();};";

webview.evaluateJavascript(js, null);

}

/**

* jquery脚本执行

*/

public void jquery_dom(String jscontent) {

String js = "var newscript = document.createElement(\"script\");";

js += "newscript.src=\"https://cdn.bootcss.com/jquery/1.12.4/jquery.min.js\";";

js += "document.body.appendChild(newscript);";

js += "newscript.οnlοad=function(){" + jscontent + "};";

webview.evaluateJavascript(js, null);

}

/**

* jquerydom点击(通过类查找)

*/

public void jquery_dom_click_byClass(String cls) {

String js = "var newscript = document.createElement(\"script\");";

js += "newscript.src=\"https://cdn.bootcss.com/jquery/1.12.4/jquery.min.js\";";

js += "document.body.appendChild(newscript);";

js += "newscript.οnlοad=function(){$('." + cls + "').click();};";

webview.evaluateJavascript(js, null);

}

/**

* jquery设置dom值

*/

public void jquery_dom_setValue(String id, String value) {

String js = "var newscript = document.createElement(\"script\");";

js += "newscript.src='https://cdn.bootcss.com/jquery/1.12.4/jquery.min.js';";

js += "document.body.appendChild(newscript);";

js += "newscript.οnlοad=function(){$('#" + id + "').val('" + value + "');};";

webview.evaluateJavascript(js, null);

}

}

执行注入

webview.setWebViewClient(new WebViewClient() {

@Override

public boolean shouldOverrideUrlLoading(WebView view, String url) {

LogUtil.logD("当前的url："+url);

view.loadUrl(url);

return true;

}

@Override

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

super.onReceivedError(view, errorCode, description, failingUrl);

LogUtil.logE(errorCode + ": " + description);

webview.loadUrl("file:///android_asset/404.html");

}

@Override

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

super.onPageStarted(view, url, favicon);

LogUtil.logD("开始加载网页:" + url);

if (!dialog.isShowing()) {

dialog.show();

}

}

@Override

public void onPageFinished(WebView view, final String url) {

super.onPageFinished(view, url);

dialog.dismiss();

LogUtil.logD("加载完成 URL：" + url);

webview.postDelayed(new Runnable() {

@Override

public void run() {

JSUtil.getInstance(webview).injectJquery(new JSUtil.InjectCallback() {

@Override

public void onSuccess() {

LogUtil.logD("执行登录：点击首页登录");

webview.evaluateJavascript("var link=$('#nav-logobar-greeting').attr('href');if(link){window.location=link;}else{$('#gwm-SignIn-button').click();}", null);

}

@Override

public void onFail() {

}

});

}

}, 1000);

}

});

注意上面的onPageFinished方法中延迟操作，如果不加这个延迟，webview.evaluateJavascript根本无法执行(找不到“$定义”)