方法一：
var windowHeight = wx.getSystemInfoSync().windowHeight
var windowWidth = wx.getSystemInfoSync().windowWidth方法二：
.windowHeightWidthClass {
height: 100vh;
width: 100vw;
}
CSS3中的 `vh` 和 `vw` 是相對(duì)于屏幕大小的單位，即：vh => view heightvw => view width