Windows Phone 7 编程实践—捕获Map控件的DoubleTap事件

lujiguo115

作品目标：Windows Phone 7 开发的实用手册
Windows Phone 7 编程实践--捕获Map控件的DoubleTap事件。
DoubleTap事件的放大功能需要下载新的地图信息，会给用户带来不小的流量负担，因此程序自主控制地图的缩放功能很有必要。
参考资料
Touch Gestures on Windows Phone

目录
提出问题    1
Map Members    1
分析问题    3
依据原有经验，重载OnManipulationStarted方法    3
从触控手势入手，判断TouchTap的手势方法中寻找曙光    3
解决问题    4
在MainPage.XAML中添加Canvas和toolkit:GestureService.GestureListener    4
添加Map控件，设置属性    5
在MainPage类中GestureListener_DoubleTap处理代码    5
Debug调试    5


提出问题

MSDN中文论坛—Windows Phone 7开发上有位朋友提出想重载Map的默认的双击事件(Double Tap)。因为双击事件的放大功能需要下载新的地图信息，误操作会给用户带来不小的流量负担。从用户的角度来思考做出的程序，肯定会大受欢迎。
Microsoft.Phone.Controls.Maps.Map默认的双击(Double Tap)事件是修改Map的ZoomLevel属性。那么Map空间的双击(Double Tap)事件如何重载呢，让我们先看看MSDN上关于Map Event的帮助。
Map Members

Windows Phone
Events

	Name	Description
	BindingValidationError	(Inherited from FrameworkElement.)
	GotFocus	(Inherited from UIElement.)
	IsEnabledChanged	(Inherited from Control.)
	KeyDown	(Inherited from UIElement.)
	KeyUp	(Inherited from UIElement.)
	LayoutUpdated	(Inherited from FrameworkElement.)
	Loaded	(Inherited from FrameworkElement.)
	LoadingError	Occurs when there is an error loading the map. (Inherited from MapCore.)
	LostFocus	(Inherited from UIElement.)
	LostMouseCapture	(Inherited from UIElement.)
	ManipulationCompleted	(Inherited from UIElement.)
	ManipulationDelta	(Inherited from UIElement.)
	ManipulationStarted	(Inherited from UIElement.)
	MapPan	Occurs when the screen is touched and dragged to pan the map. This event occurs every frame. (Inherited from MapCore.)
	MapResolved	Occurs when the map tiles are fully downloaded, regardless of whether the user is still interacting with the map. (Inherited from MapCore.)
	MapZoom	Occurs when the map is touched to zoom the map. (Inherited from MapCore.)
	ModeChanged	Occurs when the map mode changes. (Inherited from MapCore.)
	MouseEnter	(Inherited from UIElement.)
	MouseLeave	(Inherited from UIElement.)
	MouseLeftButtonDown	(Inherited from UIElement.)
	MouseLeftButtonUp	(Inherited from UIElement.)
	MouseMove	(Inherited from UIElement.)
	MouseWheel	(Inherited from UIElement.)
	SizeChanged	(Inherited from FrameworkElement.)
	TargetViewChanged	Occurs when the view towards which the map is animating changes. (Inherited from MapCore.)
	Unloaded	(Inherited from FrameworkElement.)
	ViewChangeEnd	Occurs when the view is done changing. (Inherited from MapCore.)
	ViewChangeOnFrame	Occurs for every frame of a view change. (Inherited from MapCore.)
	ViewChangeStart	Occurs when the view starts changing. (Inherited from MapCore.)

显然，在这里我们找不到关于双击(Double Tap)事件，只能靠我们自己捕获触控手势。
分析问题


依据原有经验，重载OnManipulationStarted方法


依据已有的Silverlight多点触控的经验，在MainPage类中重载OnManipulationStarted处理对于Map的触控。
首先判断触控的来源于Map的话，再去判断是否是双击手势。
protected override void OnManipulationStarted(ManipulationStartedEventArgs args)
{
if (args.OriginalSource == myMap)//myMap是定义的map的name
{
//判断手势，如果是doubleTap则处理
//Silverlight对于手势的判断，有文章专门说明Silverlight应用XNA的手势判断
//……
}
args.Complete();
base.OnManipulationStarted(args);
}
尝试发现DoubleTap触控让Map拦截处理，并没有传入OnManipulationStarted方法中。
想到如果在Map的上层添加一个透明的Button，Button的作用就是截获所有map的触控。这样做虽然达到了阻止DoubleTap事件的处理，但是缺点视乎更难以接受，放弃了所有Map自带的功能，Map的所有功能都要自己实现。
看来此路不通，那我们换一种思路，从触控手势入手，判断TouchTap的手势方法中寻找曙光。

从触控手势入手，判断TouchTap的手势方法中寻找曙光


Charles Petzold有篇文章Touch Gestures on Windows Phone介绍了Silverlight在Windows Phone中判断触控手势，文章中介绍了捕获12种手势（GestureBegin, GestureCompleted, Tap, DoubleTap, Hold, DragStarted, DragDelta, DragCompleted, Flick, PinchStarted, PinchDelta, PinchCompleted）的方法。
具体做法就是在XAML文件中做如下声明：