drawnow更新数字和处理任何未决回调。如果修改图形对象，请使用此命令，并希望立即查看屏幕上的更新。

drawnowlimitratelimits the number of updates to 20 frames per second. If it has been fewer than 50 milliseconds since the last update, or if the graphics renderer is busy with the previous change, thendrawnow丢弃新更新。如果要在循环中更新图形对象，则使用此命令，而无需查看屏幕上的每个更新。跳过更新可以创建更快的动画。正在处理未决的回调，因此您可以在动画过程中与数字进行交互。

drawnowNocallbacksdefers callbacks, such as theButtonDownFcncallback, until the next fulldrawnowcommand. Use this option if you want to prevent callbacks from interrupting your code. Deferring callbacks temporarily disables figure interactions, such as mouse clicks or resizing the figure. Deferring callbacks does not affect animation speed.

drawnowlimitrateNocallbackslimits the number of updates to 20 frames per second and skips updates if the renderer is busy. This syntax also prevents callbacks from interrupting your code, which temporarily disables figure interactions.

drawnowupdateskips updates if the renderer is busy and defers callbacks. This syntax is not recommended. Use thelimitrateoption instead.

drawnowexpose更新数字，但防御回调。不建议使用此语法。使用Nocallbacksoption instead.