xcodeブラックスクリーンの解決策：
1.cd ~/Library/Developer/Xcode/DerivedData
2.rm -fr * //注释：-fr和*是分开的
3.关闭模拟器，关闭Xcode，重新启动Xcode
重新启动后我新建一个项目，运行，OK啦。
不知道对你的有没有用，你可以试一下。我觉得这个Xcode的一个bug。碰到好多次了，真心无语。
1- restart xcode and/or restart simulator (reset content and settings) and/or restart computer.
2- click on project name in project navigator. in build settings tab, go to packaging and make sure that "Product Name" is the same that the one xcode says simulator is attaching to when running. if they are different, it will fail.
3- go to your projectname.xcodeproj folder. inside there delete anything named with your userid. when you reopen xcode those files will be recreated and it should work…
4- Manually delete the build directory for your project.
5- Go to organizer window. select Projects, select your app in the left hand side and then delete over "Derived Data"
6- Check Launch option is set to "Automatically" in Product->Edit Scheme, "Run" scheme.
7- In Project->"Edit Schemes"->Run. Change the Debugger from GDB to None (this doesn't make sense to me..).
8- Kill the process gdb-i386-apple-darwin from Activity Monitor. this is assuming gdb is not responding.
9- In "Product"->Edit Scheme. in Run, click yourappname.app, choose other, navigate to your .app in your project. now run.
10- Check that you don't have two different Info.plist in your project. if you do, remove the bad one.
11- seems like there seem to be a lot of things causing this, but one thing that worked for me was simply cleaning out the build folder by pressing Cmd+Option+Shift+K or alternately if you select the Product dropdown in the toolbar and hold the Option button you should see the "Clean Build Folder" option appear
Product->Edit Scheme->(Select the run Scheme)->Debugger->None
Terminalに入り：
launchpadからTerminalを検索
スクリーンショット
Command+shift+3: