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全景响应器
PanResponder
将几个触发调节成一个单一的触发动作。该方法可以使单一触发动作对额外的触发具有弹性,可以用来识别简单的多点触发动作。
它为响应处理程序提供了一个可预测包,这个相应处理程序是由动作应答系统提供的。对每一个处理程序,在正常事件旁提供了一个新的 gestureState
对象。 一个 gestureState
对象有以下属性:
stateID
-gestureState 的ID-在屏幕上保持至少一个触发动作的时间moveX
-最近动态触发的最新的屏幕坐标x0
-应答器横向的屏幕坐标y0
-应答器纵向的屏幕坐标dx
-触发开始后累积的横向动作距离dy
-触发开始后累积的纵向动作距离vx
-当前手势的横向速度vy
-当前手势的纵向速度numberActiveTouch
-屏幕上当前触发的数量
基本用法
componentWillMount: function() {
this._panGesture = PanResponder.create({ // Ask to be the responder: onStartShouldSetPanResponder: (evt, gestureState) => true, onStartShouldSetPanResponderCapture: (evt, gestureState) => true, onMoveShouldSetPanResponder: (evt, gestureState) => true, onMoveShouldSetPanResponderCapture: (evt, gestureState) => true, onPanResponderGrant: (evt, gestureState) => { // The guesture has started. Show visual feedback so the user knows // what is happening! // gestureState.{x,y}0 will be set to zero now
}, onPanResponderMove: (evt, gestureState) => { // The most recent move distance is gestureState.move{X,Y} // The accumulated gesture distance since becoming responder is
// gestureState.d{x,y}
}, onResponderTerminationRequest: (evt, gestureState) => true, onPanResponderRelease: (evt, gestureState) => { // The user has released all touches while this view is the // responder. This typically means a gesture has succeeded
}, onPanResponderTerminate: (evt, gestureState) => { // Another component has become the responder, so this gesture // should be cancelled
},
});
}, render: function() { return (
<View {...this._panResponder.panHandlers} />
);
},
工程实例
想要查看它的实际应用,尝试 PanResponder example in UIExplorer。
方法
static create(config: object)
@param {object} 所有应答器回调配置的增强版本,应答器回调不仅可以提供典型的 ResponderSyntheticEvent
,还可以提供 PanResponder
动作状态。在每一个典型的 onResponder*
回调中,用 PanResponder
对 Responder
做简单的替换。例如, config
对象可能看起来像如下形式:
onMoveShouldSetPanResponder: (e, gestureState) => {...}
onMoveShouldSetPanResponderCapture: (e, gestureState) => {...}
onStartShouldSetPanResponder: (e, gestureState) => {...}
onStartShouldSetPanResponderCapture: (e, gestureState) => {...}
onPanResponderReject: (e, gestureState) => {...}
onPanResponderGrant: (e, gestureState) => {...}
onPanResponderStart: (e, gestureState) => {...}
onPanResponderEnd: (e, gestureState) => {...}
onPanResponderRelease: (e, gestureState) => {...}
onPanResponderMove: (e, gestureState) => {...}
onPanResponderTerminate: (e, gestureState) => {...}
onPanResponderTerminationRequest: (e, gestureState) => {...}
一般来说,对于那些捕获的等价事件,我们在捕获阶段更新一次 gestureState ,并且也可以在冒泡阶段使用。
在 onStartShould* 回调时需要注意一点。在对节点的捕获/冒泡阶段的开始/结束事件中,它们只对更新后的gestureState
做出反应。一旦节点成为应答器,你可以依靠每一个被动作和 gestureState
处理后相应更新的开始/结束事件。 (numberActiveTouches) 可能不完全准确,除非你是应答器。