在android应用程序启动时抛出下面异常导致启动失败：
07-09 17:12:35.709: ERROR/AndroidRuntime(3866): Uncaught handler: thread main exiting due to uncaught exception
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{org.anselm.eickhoff.rhythm/org.anselm.eickhoff.rhythm.RhythmGameActivity}: java.lang.ClassNotFoundException: org.anselm.eickhoff.rhythm.RhythmGameActivity in loader dalvik.system.PathClassLoader@4001e740
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2497)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2621)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.app.ActivityThread.access$2200(ActivityThread.java:126)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1932)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.os.Handler.dispatchMessage(Handler.java:99)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.os.Looper.loop(Looper.java:123)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.app.ActivityThread.main(ActivityThread.java:4595)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at java.lang.reflect.Method.invokeNative(Native Method)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at java.lang.reflect.Method.invoke(Method.java:521)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at dalvik.system.NativeStart.main(Native Method)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): Caused by: java.lang.ClassNotFoundException: org.anselm.eickhoff.rhythm.RhythmGameActivity in loader dalvik.system.PathClassLoader@4001e740
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at java.lang.ClassLoader.loadClass(ClassLoader.java:573)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at java.lang.ClassLoader.loadClass(ClassLoader.java:532)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2489)
07-09 17:12:35.719: ERROR/AndroidRuntime(3866): ... 11 more
个人按下面顺序排查：
1.
在Manifest.xml中查看Activity的名字是否书写正确。
2.
在Manifest.xml确认Activity标签中的android:name属性的格式，例如我的activity的名字是helloworld，确认android:name=”.helloworld”（其中的点很重要）。
3.
如果有添加外部包的情况下，在工程根目录下建libs目录，然后将需要导入的外部包放入此目录内再add jars。
4.
如果上面都确保OK的情况下仍发生问题的话，clean工程->关闭eclipse->在命令行中重启adb（adb kill-server adbstart-server）->打开eclipse->编译启动。
上面4步基本能解决问题。
http://www.cnblogs.com/yyangblog/archive/2012/05/23/2514514.html
