[Dart] Flutter开发中的几个常用函数

/** 返回当前时间戳 */
  static int currentTimeMillis() {
    return new DateTime.now().millisecondsSinceEpoch;
  }

  /** 复制到剪粘板 */
  static copyToClipboard(final String text) {
    if (text == null) return;
    Clipboard.setData(new ClipboardData(text: text));
  }

  static const RollupSize_Units = ["GB", "MB", "KB", "B"];
  /** 返回文件大小字符串 */
  static String getRollupSize(int size) {
    int idx = 3;
    int r1 = 0;
    String result = "";
    while (idx >= 0) {
      int s1 = size % 1024;
      size = size >> 10;
      if (size == 0 || idx == 0) {
        r1 = (r1 * 100) ~/ 1024;
        if (r1 > 0) {
          if (r1 >= 10)
            result = "$s1.$r1${RollupSize_Units[idx]}";
          else
            result = "$s1.0$r1${RollupSize_Units[idx]}";
        } else
          result = s1.toString() + RollupSize_Units[idx];
        break;
      }
      r1 = s1;
      idx--;
    }
    return result;
  }

/** 返回两个日期相差的天数 */
  static int daysBetween(DateTime a, DateTime b, [bool ignoreTime = false]) {
    if (ignoreTime) {
      int v = a.millisecondsSinceEpoch ~/ 86400000 -
          b.millisecondsSinceEpoch ~/ 86400000;
      if (v < 0) return -v;
      return v;
    } else {
      int v = a.millisecondsSinceEpoch - b.millisecondsSinceEpoch;
      if (v < 0) v = -v;
      return v ~/ 86400000;
    }
  }

/** 获取屏幕宽度 */
  static double getScreenWidth(BuildContext context) {
    return MediaQuery.of(context).size.width;
  }

  /** 获取屏幕高度 */
  static double getScreenHeight(BuildContext context) {
    return MediaQuery.of(context).size.height;
  }

  /** 获取系统状态栏高度 */
  static double getSysStatsHeight(BuildContext context) {
    return MediaQuery.of(context).padding.top;
  }