The reason is that we need references to both ProgressBars as arguments to the callback, and at the time the Scale constructor is invoked, they are not all defined yet.

原因在于，我们需要以对两个ProgressBar的引用作为回调的参数，而当Scale构造函数被调用时，它们还没有被定义。

youdao

The reason is that we need references to both ProgressBars as arguments to the callback, and at the time the Scale constructor is invoked, they are not all defined yet.

原因在于，我们需要以对两个ProgressBar的引用作为回调的参数，而当Scale构造函数被调用时，它们还没有被定义。

youdao