After update to Android API level 21 you may face some issues while working with Android Eclipse ADT tool. One of them is appcompat_v7 theme related error messages which can be resolved by setting appcompat_v7 library project build target as 5.0
Another problem that i faced was running app on emulator while working on Mac OS X machine. The emulator simply used to load on Dock and disappear. I tried it with every emulator that i had and even tried removing snapshot option selected while the emulator was created.
Error logs on Console :
[2014-11-03 17:12:35 - App] ------------------------------
[2014-11-03 17:12:35 - App] Android Launch!
[2014-11-03 17:12:35 - App] adb is running normally.
[2014-11-03 17:12:35 - App] Performing com.example.drawing.MainActivity activity launch
[2014-11-03 17:12:37 - App] Launching a new emulator with Virtual Device 'myEmulator'
[2014-11-03 17:12:38 - App] emulator: ERROR: Unable to load VM from snapshot. The snapshot has been saved for a different hardware configuration.
My Project has minSDK version is 8 and maxSDK is 19 : But the build library was set as Android 21 causing this issue. Just select Android Build target for your App Project folder as Android 19 and this issue will be resolved.
Hope this may help someone resolve similar issue.