attachmentSimple控制只能上传一个文件，再上传提示是否替换

attachmentSimple组件默认没有提供设置上传个数的控制，如果需要控制，可以获取到组件上的uploader，在uploader上绑定事件onFileSelected进行控制
获取uploader参考：

		var attachmentSimple = this.comp("attachmentSimple3")
		var uploader = attachmentSimple.uploader;

给uploader绑定onFileSelected参考：

uploader.on('onFileSelected',function(event){
      });

控制只能上传一个文件，再上传提示是否替换可以在model的onLoad事件中如下实现：

	Model.prototype.modelLoad = function(event) {

		var attachmentSimple = this.comp("attachmentSimple3")
		var uploader = attachmentSimple.uploader;
		var data = this.comp("mainData");
		uploader.on('onFileSelected', function(event) {
			var fFJ = data.getValue("fFJ");
			var jsonList = eval("(" + fFJ + ")");
			if (jsonList != undefined && jsonList.length > 0) {// 判断是否有文件
				var storeFileName = jsonList[0]["storeFileName"];
				var ownerID = jsonList[0]["ownerID"];
				var r = confirm("只允许上传一个文件是否替换原有文件");
				if (r == true) {
					attachmentSimple1.removeItemByStoreID(storeFileName, ownerID);// 删除原来的文件
				} else {
					event.cancel = true;
				}
			}
		});
	};