调用IOS原生代码 代理没有执行 哪位大神看看为啥

function openFileIOS(filePath,title){
var QLPreviewController=plus.ios.importClass("QLPreviewController");
var fileType=filePath.substr((filePath.lastIndexOf(".")+1),filePath.length);
title=title.substr(0,title.length-fileType.length-1);
console.log(title);
var PreviewDataSource=plus.ios.implements("PreviewDataSource",{
"numberOfPreviewItemsInPreviewController:":function(previewController){
return 1;
},"previewControllerpreviewItemAtIndex:":function(previewController,index){
console.log(1111111111111);
var NSBundle=plus.ios.importClass("NSBundle");
var documentLocation = new NSBundle().pathForResource(title,fileType);
console.log(documentLocation);
var myQLDocument = plus.ios.importClass("NSURL").fileURLWithPath(documentLocation);
return myQLDocument;
},

});  
console.log(222222);  
var previewoCntroller=new QLPreviewController();  
previewoCntroller.datasource=PreviewDataSource;  
console.log(3333333333);  
//previewoCntroller.setTitle(title);  

}