wap2app iOS 剪贴板不能使用

function getClipbordText() {  

            if(!window.plus) return;  

            if(mui.os.android) {  

                var Context = plus.android.importClass("android.content.Context");  

                var main = plus.android.runtimeMainActivity();  

                var clip = main.getSystemService(Context.CLIPBOARD_SERVICE);  

                return plus.android.invoke(clip, "getText");  

            } else {  

                var UIPasteboard = plus.ios.importClass("UIPasteboard");  

                var generalPasteboard = UIPasteboard.generalPasteboard();  

                // 设置/获取文本内容:  

                generalPasteboard.setValueforPasteboardType("testValue", "public.utf8-plain-text");  

                var _val = generalPasteboard.valueForPasteboardType("public.utf8-plain-text");  

                //TODO 应用在后台的时候获取剪切版数据被系统限制了，只有在app内才能访问接口  

                //var _val=generalPasteboard.plusCallMethod({valueForPasteboardType:"public.utf8-plain-text"});  

                console.log("ios复制返回的数据是：",_val);  

                return _val || '';  

            }  

        }

wap2app iOS 模式下var UIPasteboard = plus.ios.importClass("UIPasteboard"); UIPasteboard获取为null,Android没有问题