Release your fingers and the circles will disappear.Īnother event that you can detect is gestureend. You can move the circles across the screen. If you hold these keys and move your mouse simultaneously, then the circles will be moved. By clicking on the Alt + Apple key, two circles will be displayed on the screen. In practice, using the detection and control of these events, we can enable visual effects such as drag-and-drop.ĭevelopers using the iPhone Simulator can use a shortcut to simulate the multi-touch. The events-launching mechanism offers flexibility to developers because they can program some actions as a response to these events, taking a major fine-grained control over the multi-touch screen. Finally, when the second finger is lifted from the screen, the system launches touchend for completing the sequence. This event happens immediately after gestureend.ħ. When one of the fingers is lifted from the screen, the touchend event is launched for this finger. When the user stops the movement of the fingers, a new gestureend event is launched.Ħ. If the user moves the fingers, then the gesturechange event is launched.ĥ. At this point, both fingers are touching the screen. Immediately after the gesturestart is launched, a new touchestart event is launched for the second finger.Ĥ. The second finger goes to the screen and the gesturestart event is launched.ģ. The user touches the screen using one finger and then the touchstart event is launched.Ģ. In this case, the complete sequence of events is as follows:ġ. One clear example of this process is when the user makes use of a two-finger swipe across the screen. Actually, the sequence for multi-touch events combines both kinds of classes. Therefore, both of these are triggered when a multi-touch event occurs. Also the objects belonging to this class encapsulate TouchEvent objects. How it works…įrom the technical point of view, the class GestureEvent encapsulates the information about a multi-touch event. You’ll find the code for this recipe at: code/ch03/multi-touch.html in the code bundle. The next two screenshots show different messages displayed for each event: Obviously, one handler is required to respond to this event, so we’ll use the following JavaScript function:ĥ. This action is very simple, you only need the next line:Ĥ. For this case, we’re going to replace the attribute ongesturestart for ongesturemove. Also, you can detect if the user moves the finger across the screen. At this point, we can detect when the user touches the screen with one or more fingers.
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