今天将ADT升级后(adnroid SDK Tools从20升级到22, Android SDK Build-tools升级到17)，突然所有程序不能启动了，报找不到R类，然后layout并没有错误，bin文件夹下也没有生成R.java类，后发现是Android SDK Tools等没有安装。

在Android SDK Manager中安装完Tools文件夹下tools后依然不能启动，异常如下：

E/AndroidRuntime(12439): FATAL EXCEPTION: main
E/AndroidRuntime(12439): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{cn.trinea.android.demo/cn.trinea.android.demo.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "cn.trinea.android.demo.MainActivity" on path: DexPathList[dexElements=[zip file "/data/app/cn.trinea.android.demo-1.apk"],nativeLibraryDirectories=[/data/app-lib/cn.trinea.android.demo-1, /vendor/lib, /system/lib]]
E/AndroidRuntime(12439): 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2382)
E/AndroidRuntime(12439): 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2520)
E/AndroidRuntime(12439): 	at android.app.ActivityThread.access$600(ActivityThread.java:168)
E/AndroidRuntime(12439): 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1360)
E/AndroidRuntime(12439): 	at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(12439): 	at android.os.Looper.loop(Looper.java:153)
E/AndroidRuntime(12439): 	at android.app.ActivityThread.main(ActivityThread.java:5508)
E/AndroidRuntime(12439): 	at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(12439): 	at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(12439): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:835)
E/AndroidRuntime(12439): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
E/AndroidRuntime(12439): 	at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(12439): Caused by: java.lang.ClassNotFoundException: Didn't find class "cn.trinea.android.demo.MainActivity" on path: DexPathList[dexElements=[zip file "/data/app/cn.trinea.android.demo-1.apk"],nativeLibraryDirectories=[/data/app-lib/cn.trinea.android.demo-1, /vendor/lib, /system/lib]]
E/AndroidRuntime(12439): 	at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:53)
E/AndroidRuntime(12439): 	at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
E/AndroidRuntime(12439): 	at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
E/AndroidRuntime(12439): 	at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
E/AndroidRuntime(12439): 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2373)
E/AndroidRuntime(12439): 	... 11 more

解决方法：

菜单Project -> Properties -> Java Build Path -> Order & Export, 然后选中Android Private Libraries, 菜单 Project->Clean，然后运行程序即可。

如果依然失败，将相关的依赖工程选中Android Private Libraries并clean然后重试即可

PS:

新版的ADT加快了插件启动速度，增加了Dump View Hierarchy for UI Automator使得界面查看更方便，Capature System Wide Trace貌似是用来性能调优的，不过不支持windows，后面详细了解看看