nuttyreading-html/uni_modules/z-paging/components/z-paging/z-paging-refresh.wxs

// z-paging
// github地址:https://github.com/SmileZXLee/uni-z-paging
// dcloud地址:https://ext.dcloud.net.cn/plugin?id=3935
// 反馈QQ群：790460711

//微信小程序、QQ小程序、app-vue、h5上使用wxs实现自定义下拉刷新，降低逻辑层与视图层的通信折损，提升性能

function propObserver(newValue, oldValue, ownerInstance, instance) {
	var state = ownerInstance.getState();
	state.currentInstance = instance;
	var dataset = instance.getDataset();
	var loading = dataset.loading == true;
	if (newValue.indexOf('end') != -1) {
		_setTransform('translateY(0px)', instance)
		state.moveDistance = 0;
	} else if (newValue.indexOf('begin') != -1) {
		var refresherThreshold = instance.getDataset().refresherthreshold
		_setTransformValue(refresherThreshold, instance, state);
	}
}

function touchstart(e, ownerInstance) {
	var instance = ownerInstance.getState().currentInstance;
	var state = instance.getState();
	if (_getRefresherTouchDisabled(e, instance)) {
		return;
	}
	var touch = _getCommonTouch(e);
	state.startY = touch.touchY;
	state.lastRefresherTouchmove = touch;
	ownerInstance.callMethod('_handleRefresherTouchstart', touch);
}

function touchmove(e, ownerInstance) {
	var touch = _getCommonTouch(e);
	var instance = ownerInstance.getState().currentInstance;
	var dataset = instance.getDataset();
	var refresherThreshold = dataset.refresherthreshold;
	var isTouchmoving = _getIsTrue(instance.getDataset().istouchmoving);
	var state = instance.getState();
	if (_getRefresherTouchDisabled(e, instance)) {
		return;
	}
	if (!_getAngleIsInRange(e, touch, state, dataset)) {
		return;
	}
	var moveDistance = _getMoveDistance(e, instance);
	if (moveDistance < 0) {
		return;
	}
	if (e.preventDefault) {
		e.preventDefault();
	}
	_setTransformValue(moveDistance, instance, state);
	var oldRefresherStatus = state.refresherStatus;
	if (moveDistance >= refresherThreshold) {
		state.refresherStatus = 1;
	} else {
		state.refresherStatus = 0;
	}
	if (oldRefresherStatus == undefined || oldRefresherStatus != state.refresherStatus || !isTouchmoving) {
		ownerInstance.callMethod('_handleRefresherTouchmove', moveDistance, touch);
	}
	return false;
}

function touchend(e, ownerInstance) {
	var touch = _getCommonTouch(e);
	var instance = ownerInstance.getState().currentInstance;
	var dataset = instance.getDataset();
	var state = instance.getState();
	if (_getRefresherTouchDisabled(e, instance)) {
		return;
	}
	state.refresherReachMaxAngle = true;

	var isTouchmoving = _getIsTrue(instance.getDataset().istouchmoving);
	if (!isTouchmoving) {
		return;
	}
	var oldMoveDistance = state.moveDistance;
	var refresherThreshold = instance.getDataset().refresherthreshold
	var moveDistance = _getMoveDistance(e, instance);
	ownerInstance.callMethod('_handleRefresherTouchend', moveDistance);
	if (oldMoveDistance < refresherThreshold) {
		return;
	}
	if (moveDistance >= refresherThreshold) {
		moveDistance = refresherThreshold;
	}
	_setTransformValue(moveDistance, instance, state)
}


function _setTransformValue(value, instance, state) {
	value = value || 0;
	state.moveDistance = value;
	_setTransform('translateY(' + value + 'px)', instance);
}

function _setTransform(transform, instance) {
	instance.requestAnimationFrame(function() {
		instance.setStyle({
			transform: transform,
			'-webkit-transform': transform
		})
	})

}

function _getMoveDistance(e, instance) {
	var state = instance.getState()
	var refresherThreshold = instance.getDataset().refresherthreshold
	var touch = _getCommonTouch(e);
	var moveDistance = touch.touchY - state.startY;
	moveDistance = _getFinalRefresherMoveDistance(moveDistance, refresherThreshold);
	return moveDistance;
}

function _getCommonTouch(e) {
	var touch = null;
	if (e.touches && e.touches.length) {
		touch = e.touches[0];
	} else if (e.changedTouches && e.changedTouches.length) {
		touch = e.changedTouches[0];
	} else if (e.datail && e.datail !== {}) {
		touch = e.datail;
	} else {
		return {
			touchX: 0,
			touchY: 0
		}
	}
	return {
		touchX: touch.clientX,
		touchY: touch.clientY
	};
}

function _getFinalRefresherMoveDistance(moveDistance, refresherThreshold) {
	refresherThreshold = parseFloat(refresherThreshold);
	moveDistance = moveDistance * 0.7;
	if (moveDistance >= refresherThreshold) {
		moveDistance = refresherThreshold + (moveDistance - refresherThreshold) * 0.3;
	}
	return moveDistance;
}


function _getRefresherTouchDisabled(e, instance) {
	var dataset = instance.getDataset();
	var loading = _getIsTrue(dataset.loading);
	var useChatRecordMode = _getIsTrue(dataset.usechatrecordmode);
	var refresherEnabled = _getIsTrue(dataset.refresherenabled);
	var useCustomRefresher = _getIsTrue(dataset.usecustomrefresher);
	var usePageScroll = _getIsTrue(dataset.usepagescroll);
	var pageScrollTop = parseFloat(dataset.pagescrolltop);
	var wxsIsScrollTopInTopRange = _getIsTrue(dataset.wxsisscrolltopintoprange);
	var scrollTop = parseFloat(dataset.scrolltop);
	var res = loading || useChatRecordMode || !refresherEnabled || !useCustomRefresher || (
		usePageScroll && useCustomRefresher && pageScrollTop > 10) || (!(
		usePageScroll && useCustomRefresher) && !wxsIsScrollTopInTopRange);
	return res;
}

function _getAngleIsInRange(e, touch, state, dataset) {
	var refresherMaxAngle = dataset.refreshermaxangle;
	var refresherAecc = _getIsTrue(dataset.refresheraecc);
	var lastRefresherTouchmove = state.lastRefresherTouchmove;
	var moveDistance = state.moveDistance;
	var refresherReachMaxAngle = state.refresherReachMaxAngle;
	if (!lastRefresherTouchmove) {
		return true;
	}
	if (refresherMaxAngle >= 0 && refresherMaxAngle <= 90 && lastRefresherTouchmove) {
		if (!refresherAecc && refresherReachMaxAngle != null && !refresherReachMaxAngle) {
			return false;
		}
		var x = Math.abs(touch.touchX - lastRefresherTouchmove.touchX);
		var y = Math.abs(touch.touchY - lastRefresherTouchmove.touchY);
		var z = Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2));
		if (x && y) {
			var angle = Math.asin(y / z) / Math.PI * 180;
			if (angle < refresherMaxAngle) {
				state.lastRefresherTouchmove = touch;
				state.refresherReachMaxAngle = false;
				return false;
			}
		}
	}
	state.lastRefresherTouchmove = touch;
	return true;
}

function _getIsTrue(value) {
	value = (typeof(value) === 'string' ? JSON.parse(value) : value) || false;
	return value == true || value == 'true';
}

module.exports = {
	touchstart: touchstart,
	touchmove: touchmove,
	touchend: touchend,
	propObserver: propObserver
}