差量更新后 还是会自动启动dtask.start() 下载更新文件

function downWgt (location){
alert("downWgtdsafdasd");
var url=location;
plus.nativeUI.showWaiting("升级中...");
var dtask = plus.downloader.createDownload( url, {method:"GET"}, function(d,status){
if ( status == 200 ) {

        console.log( "Download wgtu success: " + d.filename );  
        plus.runtime.install(d.filename,{},function(){  

            plus.nativeUI.closeWaiting();  

            plus.nativeUI.alert("Update wgtu success, restart now!",function(){  

                plus.runtime.restart();  

            });  
        },function(e){  
            plus.nativeUI.closeWaiting();  
            alert("Update wgtu failed: "+e.message);  
        });  
    } else {  
        plus.nativeUI.closeWaiting();  
         alert( "Download wgtu failed: " + status );   
    }   
} );  
dtask.addEventListener('statechanged',function(d,status){  
    console.log("statechanged: "+d.state);  
});  
dtask.start();  

                      }