webview.getSettings 始终返回null

            var Webview = plus.android.importClass("android.webkit.WebView");  
            var WebSettings = plus.android.importClass("android.webkit.WebSettings");  
            var wv = this.$scope.$getAppWebview();  
            var setting = plus.android.invoke(wv, "getSettings");  
            console.log(setting); //null  
            try{  
                setting=wv.getSettings();  
                console.log(setting);  
            }catch(e){  
                //TODO handle the exception  
                console.log(e);  
            }  
            var nwv=wv.nativeInstanceObject();  
            setting = plus.android.invoke(nwv, "getSettings");  
            console.log(setting);  
            setting=nwv.getSettings();  
            console.log(setting);

输出四个结果,第二个捕获异常输出: TypeError: wv.getSettings is not a function 其它三个都是null
也就是webview.getSettings无法返回settings