[英]How to: Dynamically set <BODY> background-position?
我以前發布了一個問題,但這個問題已經脫離話題了,我在重新發布我擁有VERIFIED與iPhone兼容的更好的代碼(無論如何我的作品都可以!)
我只想將背景位置坐標應用於body元素,並有條件地為iPhone,iPod和iPad調用腳本。 這是我對這些設備的有條件要求:
var deviceAgent = navigator.userAgent.toLowerCase();
var agentID = deviceAgent.match(/(iphone|ipod|ipad)/);
if (agentID) {
// do something
} else {
//do this
}
現在,我發現了這個出色的腳本,它可以根據滾動位置動態設置“ top:x”。 每個人都告訴我(以及所有教程和Google搜索結果),由於視口問題,無法為iPhone動態設置滾動位置。 但是,它們是錯誤的,因為如果您滾動到頁面底部並在iPhone上查看此javascript演示,則可以滾動和
<div style="background-position: fixed; top: x (variable)"></div>
div確實以iPhone為中心。 我真的希望這個問題能對很多人有所幫助,我以為這是不可能的,但事實並非如此……我只需要幫助將它們縫合在一起即可!
原始代碼(您可以自己在iPhone上測試)在這里: http : //stevenbenner.com/2010/04/calculate-page-size-and-view-port-position-in-javascript/
**編輯:供參考,這是通過動態應用“ top:x”元素來做到絕對位置本身的div(即使在iPhone上):
http://stevenbenner.com/2010/04/calculate-page-size-and-view-port-position-in-javascript/ **
因此,我只需要獲取以下代碼的幫助,即可將動態“ background-position:0 x”應用於BODY標簽,其中x居中且相對於視口位置。 同樣,需要嵌套在上述代碼中,這對於iPhone和類似設備是有條件的。
// Page Size and View Port Dimension Tools
// http://stevenbenner.com/2010/04/calculate-page-size-and-view-port-position-in-javascript/
if (!sb_windowTools) { var sb_windowTools = new Object(); };
sb_windowTools = {
scrollBarPadding: 17, // padding to assume for scroll bars
// EXAMPLE METHODS
// center an element in the viewport
centerElementOnScreen: function(element) {
var pageDimensions = this.updateDimensions();
element.style.top = ((this.pageDimensions.verticalOffset() + this.pageDimensions.windowHeight() / 2) - (this.scrollBarPadding + element.offsetHeight / 2)) + 'px';
element.style.left = ((this.pageDimensions.windowWidth() / 2) - (this.scrollBarPadding + element.offsetWidth / 2)) + 'px';
element.style.position = 'absolute';
},
// INFORMATION GETTERS
// load the page size, view port position and vertical scroll offset
updateDimensions: function() {
this.updatePageSize();
this.updateWindowSize();
this.updateScrollOffset();
},
// load page size information
updatePageSize: function() {
// document dimensions
var viewportWidth, viewportHeight;
if (window.innerHeight && window.scrollMaxY) {
viewportWidth = document.body.scrollWidth;
viewportHeight = window.innerHeight + window.scrollMaxY;
} else if (document.body.scrollHeight > document.body.offsetHeight) {
// all but explorer mac
viewportWidth = document.body.scrollWidth;
viewportHeight = document.body.scrollHeight;
} else {
// explorer mac...would also work in explorer 6 strict, mozilla and safari
viewportWidth = document.body.offsetWidth;
viewportHeight = document.body.offsetHeight;
};
this.pageSize = {
viewportWidth: viewportWidth,
viewportHeight: viewportHeight
};
},
// load window size information
updateWindowSize: function() {
// view port dimensions
var windowWidth, windowHeight;
if (self.innerHeight) {
// all except explorer
windowWidth = self.innerWidth;
windowHeight = self.innerHeight;
} else if (document.documentElement && document.documentElement.clientHeight) {
// explorer 6 strict mode
windowWidth = document.documentElement.clientWidth;
windowHeight = document.documentElement.clientHeight;
} else if (document.body) {
// other explorers
windowWidth = document.body.clientWidth;
windowHeight = document.body.clientHeight;
};
this.windowSize = {
windowWidth: windowWidth,
windowHeight: windowHeight
};
},
// load scroll offset information
updateScrollOffset: function() {
// viewport vertical scroll offset
var horizontalOffset, verticalOffset;
if (self.pageYOffset) {
horizontalOffset = self.pageXOffset;
verticalOffset = self.pageYOffset;
} else if (document.documentElement && document.documentElement.scrollTop) {
// Explorer 6 Strict
horizontalOffset = document.documentElement.scrollLeft;
verticalOffset = document.documentElement.scrollTop;
} else if (document.body) {
// all other Explorers
horizontalOffset = document.body.scrollLeft;
verticalOffset = document.body.scrollTop;
};
this.scrollOffset = {
horizontalOffset: horizontalOffset,
verticalOffset: verticalOffset
};
},
// INFORMATION CONTAINERS
// raw data containers
pageSize: {},
windowSize: {},
scrollOffset: {},
// combined dimensions object with bounding logic
pageDimensions: {
pageWidth: function() {
return sb_windowTools.pageSize.viewportWidth > sb_windowTools.windowSize.windowWidth ?
sb_windowTools.pageSize.viewportWidth :
sb_windowTools.windowSize.windowWidth;
},
pageHeight: function() {
return sb_windowTools.pageSize.viewportHeight > sb_windowTools.windowSize.windowHeight ?
sb_windowTools.pageSize.viewportHeight :
sb_windowTools.windowSize.windowHeight;
},
windowWidth: function() {
return sb_windowTools.windowSize.windowWidth;
},
windowHeight: function() {
return sb_windowTools.windowSize.windowHeight;
},
horizontalOffset: function() {
return sb_windowTools.scrollOffset.horizontalOffset;
},
verticalOffset: function() {
return sb_windowTools.scrollOffset.verticalOffset;
}
}
};
<?php
/* detect Mobile Safari */
$browserAsString = $_SERVER['HTTP_USER_AGENT'];
if (strstr($browserAsString, " AppleWebKit/") && strstr($browserAsString, " Mobile/"))
{
$browserIsMobileSafari = true;
echo
"
<script>
$(document).ready(function() {
$(window).scroll(function() {
windowPosition = $(this).scrollTop();
$('body').stop().animate({'backgroundPositionY' : windowPosition+'px'}, 500);
});
});
</script>
"
;} ?>
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