WebView加载http、https细节，交互及注意事项

一、源码：

@SuppressLint("SetJavaScriptEnabled")
    public void initWebView() {
        webView.setWebViewClient(new CusWebViewClient());
        webView.setWebChromeClient(new CusWebChromeClient());
        WebSettings setting = webView.getSettings();
        setting.setJavaScriptEnabled(true);
        setting.setAllowFileAccess(true);
        String dir = getApplicationContext().getCacheDir().getAbsolutePath();

        setting.setDomStorageEnabled(true);// 开启 DOM storage API 功能
        setting.setGeolocationEnabled(true);
        setting.setUserAgentString("Mozilla/5.0 (Linux; Android 6.0.1; SM-G920V Build/MMB29K) AppleWebKit/537.36 " +
                "(KHTML, like Gecko) Chrome/52.0.2743.98 Mobile Safari/537.36");
        setting.setRenderPriority(RenderPriority.HIGH);
        setting.setCacheMode(WebSettings.LOAD_DEFAULT); // 设置 缓存模式
        setting.setAppCachePath(dir);// 设置 Application Caches 缓存目录
        // 开启 Application Caches 功能
        setting.setAppCacheEnabled(true); // 开启 Application Caches 功能
        setting.setDefaultTextEncodingName("UTF-8");// 设置字符编码
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            Log.v(TAG, "版本大于21，启动setMixedContentMode(0)");
            setting.setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW); // 解决http及https混合情况下页面加载问题
        } else {
            Log.v(TAG, "版本小于21，无须启动setMixedContentMode(0)");
        }
        // 让网页适配手机
        setting.setUseWideViewPort(true);
        setting.setLoadWithOverviewMode(true);
        webView.setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY);// 滚动条风格，为0指滚动条不占用空间，直接覆盖在网页上
        webView.addJavascriptInterface(new Contact(), "contact");
        loadWeb(currentUrl);
    }

private class CusWebViewClient extends WebViewClient {
        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon) {// 网页页面开始加载的时候
            if (WebActivity.this.isFinishing()) {
                return;
            }
            Log.e(TAG, "--onPageStarted()--, url : " + url);
            showProgress("加载中");
            webView.setEnabled(false);// 当加载网页的时候将网页进行隐藏
            super.onPageStarted(view, url, favicon);
        }

        @Override
        public void onPageFinished(WebView view, String url) {// 网页加载结束的时候
            Log.e(TAG, "onPageFinished , url : " + url);
            hidProgress();
            webView.setEnabled(true);
            if (!mLoadError) {
                webView.setVisibility(View.VISIBLE);
                errorWebView.setVisibility(View.GONE);
            }
            super.onPageFinished(view, url);
        }

        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) { // 网页加载时的连接的网址
            Log.d(TAG, "页面加载href:" + url);
            loadWeb(url);
            return true;
        }

        @SuppressWarnings("deprecation")
        @Override
        public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
            Log.e(TAG, "onReceivedError, errorCode : " + errorCode + ", failingUrl : " + failingUrl + ", description : " + description);
            if (failingUrl.equals(currentUrl)) {
                loadFailtUrl();
            }
        }

        @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
        @Override
        public void onReceivedHttpError(WebView view, WebResourceRequest request, WebResourceResponse errorResponse) {
            String reqUrl = request.getUrl().toString();
            Log.e(TAG, "onReceivedHttpError, reqUrl : " + reqUrl + ", currentUrl : " + currentUrl);
            if (reqUrl.equals(currentUrl)) {
                loadFailtUrl();
            }
        }

        @Override
        public void onReceivedSslError(WebView view, SslErrorHandler handler, SslError error) {
            Log.e(TAG, "error : " + error);
            // 接受所有网站的证书
            handler.proceed();
            // 默认是handler.cancel();
//            super.onReceivedSslError(view, handler, error);
        }
    }

    static class CusWebChromeClient extends WebChromeClient 
    {
        @Override
        public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
            return super.onJsAlert(view, url, message, result);
        }

        @Override
        public void onReceivedTitle(WebView view, String title) {
            // 404 , 502 Bad Gateway...
            Log.e(TAG, "onReceivedTitle : " + title);
            super.onReceivedTitle(view, title);
        }
    }

/*****************
     * Android与JS交互接口
     **************************/

    private final class Contact {
        // JavaScript调用此方法

        /**
         * 关闭当前的原生界面
         */
        @JavascriptInterface
        public void goBack() {
            // 调用JS中的方法
            finish();
        }
}

二、Android调用Js：
1.通过loadUrl()：

// 此方法能调用js函数，但无法直接获取js函数的返回值。需要js再调用一个android方法把返回值传
// 过来才行
webView.loadUrl("javascript:attentionBtnClick('" + finalButtonTxt + "', '" + 
finalButtomId + "')");

2.通过evaluateJavascript()：

// 此方法需要 api>= 19才能用。此法能直接获取js的返回值
webView.evaluateJavascript("getContent()", new ValueCallback<String>() {
            @Override
            public void onReceiveValue(String value) {
                Log.e(TAG, "--- evaluateJavascript --- js 返回值 ： " + value);
                showMsg(value, Toast.LENGTH_SHORT);
            }
        });

三、Js调用Android：

window.contact.goBack();

四、WebView加载https：

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            settings.setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
        }

webView.setWebViewClient(new WebViewClient(){
            @Override
            public void onReceivedSslError(WebView view, SslErrorHandler handler, 
            SslError error) {
                // 接受所有网站的证书
            handler.proceed();
            // 默认是handler.cancel();
//            super.onReceivedSslError(view, handler, error);
            }
        });

五、WebView加载http及https混合页面（例如，https页面有一个http的图片）：

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            Log.v(TAG, "版本大于21，启动setMixedContentMode(0)");
             // 解决http及https混合情况下页面加载问题
 setting.setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
        } else {
            Log.v(TAG, "版本小于21，无须启动setMixedContentMode(0)");
        }