viewport width 固定宽度 在andriod 下JS处理

<script type="text/javascript">
	var mengvalue = -1;
	//if(mengvalue<0){mengvalue=0;}
	var phoneWidth = parseInt(window.screen.width);
	var phoneScale = phoneWidth / 640;

	var ua = navigator.userAgent;
	if (/Android (d+.d+)/.test(ua)) {
		var version = parseFloat(RegExp.$1);
		// andriod 2.3
		if (version > 2.3) {
			document.write('<meta name="viewport" content="width=640, minimum-scale = ' + phoneScale + ', maximum-scale = ' + phoneScale + ', target-densitydpi=device-dpi">');
			// andriod 2.3以上
		} else {
			document.write('<meta name="viewport" content="width=640, target-densitydpi=device-dpi">');
		}
		// 其他系统
	} else {
		document.write('<meta name="viewport" content="width=640, user-scalable=no, target-densitydpi=device-dpi">');
	}
</script>