我正在慢慢学习如何使用WPF的.NET Reactive Extensions.有一些初学者的例子说明编写拖放或绘图例程是多么简单,但它们都非常简单.我试图更进一步,对我而言,"正确"方式是什么并不明显.
这些例子都告诉你如何从定义事件流MouseDown,MouseMove以及MouseUp
var mouseDown = from evt in Observable.FromEvent<MouseButtonEventArgs>(..., "MouseDown")
select evt.EventArgs.GetPosition(...);
var mouseMoves = from evt in Observable.FromEvent<MouseEventArgs>(..., "MouseMove")
select evt.EventArgs.GetPosition(...);
var mouseUp = Observable.FromEvent<MouseButtonEventArgs>(..., "MouseUp");
然后如何在a期间轻松完成任务MouseDrag(这将显示从起始拖动点到当前鼠标位置创建的矩形的坐标)
var mouseDrag = from start in mouseDown
from currentPosition in mouseMoves.TakeUntil(mouseUp)
select new Rect(Math.Min(start.X, currentPosition.X),
Math.Min(start.Y, currentPosition.Y),
Math.Abs(start.X - currentPosition.X),
Math.Abs(start.Y - currentPosition.Y));
mouseDrag.Subscribe(x =>
{
Info.Text = x.ToString();
});
我的问题是,在鼠标拖动结束时完成任务的"正确"方法是什么？最初,我以为我可以这样做:
mouseDrag.Subscribe(
onNext: x =>
{
Info.Text = x.ToString();
},
onCompleted: …我有这样一个数据库:
-------------------------------------------------------------------
| id_one | id_two | timestamp_one | timestamp_two |
-------------------------------------------------------------------
| 27 | 35 | 9:30 | NULL |
-------------------------------------------------------------------
| 35 | 27 | NULL | 9:35 |
-------------------------------------------------------------------
| 27 | 35 | 9:34 | NULL |
-------------------------------------------------------------------
| 35 | 27 | NULL | 9:33 |
-------------------------------------------------------------------
我需要拉4行
ORDER BY 'timestamp_one' if 'id_one'=27 or
ORDER BY 'timestamp_two' if 'id_one'=27
这是我现在的声明:
SELECT * FROM tablename
WHERE id_one=27 OR id_two=27
ORDER BY
CASE WHEN id_one=27 THEN timestamp_one …这样做的正确方法是什么:
_bstr_t description;
errorInfo->GetDescription( &description.GetBSTR() );
要么:
_bstr_t description;
errorInfo->GetDescription( description.GetAddress() );
在哪里IError:GetDescription定义为:
HRESULT GetDescription (BSTR *pbstrDescription);
我知道我可以轻松地做到这一点:
BSTR description= SysAllocString (L"Whateva"));
errorInfo->GetDescription (&description);
SysFreeString (description);
谢谢
最近我一直在C中进行一些数值方法编程.对于错误修复和故障排除,很好地对所发生的事情进行一些直观表示.到目前为止,我一直在将数组区域输出到标准输出,但这并没有提供太多信息.我也和gnuplot一起玩了一下,但我不能得到它只保存图像,而不是坐标系和所有其他的东西.
所以我正在寻找一个教程或者一个库来向我展示如何将数组从c保存到图像中,能够保存到彩色图像会特别好.从数值到颜色的转换不是问题,我可以计算出来.如果有人指出我在这个领域的一些有用的库的方向,那将是一件好事.
最好的祝福
我刚开始学习C++.
当我执行我的代码时,它跳出程序没有任何错误.为什么？
#include "stdafx.h"
#include <iostream>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
char s1[20],s2[10];
cout<<" enter a number : ";
cin.get(s1,19);
cout<<" enter a number : ";
cin.get(s2,9);
cout<<s1<<"/n"<<s2;
getch();
}
有人知道如何启用拖放到treepanel的叶节点上吗？
我的场景与此完全相同:http://dev.sencha.com/deploy/dev/examples/tree/reorder.html 但我还需要将项目附加到叶节点.
谢谢
我有这个数据库,我必须捕获很多是/否的问题,用户的首选方法是复选框.一切都按照应有的方式运作,除非涉及到后悔和展示价值观.未选中框返回值"0"
无论如何要么忽略并且不在报告中显示"0"或者将默认值从"0"更改为空白"
使用Zend_DB的更新语句时,如何传递mysql的CURRENT_TIMESTAMP？以下似乎不起作用.
我有这样的事情:
$update = array(
'Name' => 'John',
'DT_Modified' => 'CURRENT_TIMESTAMP'
);
$db->update('usertable', $update );
运行如下所示的查询:
UPDATE usertable SET Name='John', DT_Modified = CURRENT_TIMESTAMP
根据文档,hibernate 3.6应该支持java.util.UUID类型.但是当我将其映射为:
@Id protected UUID uuid;
我得到以下异常:
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [test-applicationContext.xml]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: persistenceUnit] Unable to build EntityManagerFactory
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1420) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:291) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:288) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:190) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.findDefaultEntityManagerFactory(PersistenceAnnotationBeanPostProcessor.java:529) ~[spring-orm-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.findEntityManagerFactory(PersistenceAnnotationBeanPostProcessor.java:495) ~[spring-orm-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor$PersistenceElement.resolveEntityManager(PersistenceAnnotationBeanPostProcessor.java:656) ~[spring-orm-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor$PersistenceElement.getResourceToInject(PersistenceAnnotationBeanPostProcessor.java:629) ~[spring-orm-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:147) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:84) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]
at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.postProcessPropertyValues(PersistenceAnnotationBeanPostProcessor.java:338) ~[spring-orm-3.0.5.RELEASE.jar:3.0.5.RELEASE]
... …