问题
I have been working on an app in iphone simulator for a number of weeks and it has been running well up until now, but all of a sudden has begun running very slow both when loading content and animations. I have not made any changes to my code since I last tested it successfully.
I tried restarting the simulator (multiple times) and removing the app and doing a completely clean rebuild, but no luck. I also checked my cpu usage through the monitor while the simulator is running and I am only using about 30% of my cpu and 40% of memory.
I fully understand that the simulator is never a quick as the device itself, but it seems strange that it has suddenly started running slow after such a long time, and by slow I mean less than a quarter of its original speed.
回答1:
In the iOS simulator, at the bar on the top, click on Debug → Toggle Slow Animations (or Slow Animations with Xcode 10+). Chances are you accidentally toggled it on.
回答2:
Simple Command + T will fix this problem.
Command + T toggles the simulator's Slow Animations, which can be found under the Simulator Menu: Debug -> Slow Animations.
回答3:
Go to the simulator's Debug menu and select "Toggle Slow Animations".
Update: In Xcode 10, it's just "Slow Animations":
回答4:
Select Simulator,
Select Debug and uncheck slow animation.
shortcut
command + t
That's work for me.
回答5:
If the Cmd-T (slow animations) option doesn't work for you and Debug -> Slow Animations is off but you still have slow animations try Simulator -> Reset Contents and Settings (or possibly Hardware -> Erase All Content and Settings). That worked for me when none of the other answers in here did. Anyone have a suggestion as to why?
Also having a debugger attached (at all) may make the animations very slow.
回答6:
Another potential fix for React-Native users:
Chrome de-prioritizes Javascript running in any tabs not in the foreground. So if you have enabled remote debugging, be sure to put the debugger in its own window.
回答7:
You accidentally pressed the slow animation on debug when using simulator. So Run Simulator -> Debug -> Uncheck Slow Animation.
回答8:
I think you pressed command + T instead of command + R by mistake.
回答9:
I don't have the rep yet to leave a comment, but I upvoted some answers here and wanted to say more. I had a problem with slow animations in the iOS Simulator, especially on rotation, and I found this post via Google. Indeed, somehow "Toggle Slow Animations" must have been on, because three shifts fixed it. At first, I didn't think this was a problem because there's no checkmark next to "Toggle Slow Animations." It turns out there's never a checkmark, or any indication from the menu whether it's on or off. So just try toggling it and see if the rotation/navigation is faster/slower.
So, thank you!
回答10:
Simulator -> Reset contents and settings works for me. The issue seems to reappear when I debug my react-native code remotely. It could also be to do with AsyncStorage as nomad suggested.
回答11:
You can try to turn off remote debugging (Cmd-D -> Stop Remote JS Debugging). That usually speed things up.
回答12:
When the chrome debug is active and the browser tab is not in the foreground, the emulator is slow too. For me, I decided to put the guide in the foreground.
来源：https://stackoverflow.com/questions/15348699/iphone-simulator-suddenly-started-running-very-slow