页面在ipad中点击范围错位

Question

项目在ipad中打开后 发现点击按钮有效位置和显示位置不一样 时好时坏~~
比如点击登录按钮要点击大约上面一块的位置才会触发登录的事件 而在手机端和pc是没有问题的 有大神知道这是什么问题么

这是我的适配代码

var phoneWidth = parseInt(window.screen.width);
    var phoneScale = phoneWidth / 640;
    var ua = navigator.userAgent;
    if (/OKchexian/.test(ua) || /MicroMessenger/.test(ua)) {
      if (/Android (\d+\.\d+)/.test(ua)) {
        var version = parseFloat(RegExp.$1);

        var chromeVersion = 0;
        if (/Chrome\/(\d+\.\d+)/.test(ua)) {
          chromeVersion = parseFloat(RegExp.$1);
        }
        // andriod 2.3
        if (version > 2.3 && chromeVersion < 40.0) {
          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">');
      }
    } else {
      document.write('<meta name="viewport" content="width=640, minimum-scale = ' + phoneScale + ', maximum-scale = ' + phoneScale + ', target-densitydpi=device-dpi">');
    }