我从Github下载了一个名为Android Maps Extensions的库。
我可以在运行Android 4.0.4的Samsung Note（GT-N7000）上以调试模式运行该库的演示。
如果我点击应用程序内部的按钮，应用程序将停止，屏幕将变为黑色，几秒钟后，会出现一个对话框，显示：
Unfortunately, Android Maps Extensions has stopped.
我不确定发生了什么。 logcat输出如下所示：
01-05 01:09:17.118: I/Process(24896): Sending signal. PID: 24896 SIG: 9
01-05 01:26:43.328: D/CLIPBOARD(27226): Hide Clipboard dialog at Starting input: finished by someone else... !
01-05 01:27:09.043: D/dalvikvm(27226): GC_CONCURRENT freed 56K, 2% free 14452K/14663K, paused 2ms+3ms
01-05 01:27:09.053: W/GooglePlayServicesUtil(27226): Certificate is not yet valid.
01-05 01:27:09.053: W/GooglePlayServicesUtil(27226): Google Play Store signature invalid.
01-05 01:27:09.053: W/GooglePlayServicesUtil(27226): Certificate is not yet valid.
01-05 01:27:09.053: W/GooglePlayServicesUtil(27226): Google Play Store signature invalid.
01-05 01:27:09.058: W/GooglePlayServicesUtil(27226): Certificate is not yet valid.
01-05 01:27:09.058: W/GooglePlayServicesUtil(27226): Google Play Store signature invalid.
01-05 01:27:09.058: W/GooglePlayServicesUtil(27226): Certificate is not yet valid.
01-05 01:27:09.058: W/GooglePlayServicesUtil(27226): Google Play Store signature invalid.
01-05 01:27:09.063: W/GooglePlayServicesUtil(27226): Certificate is not yet valid.
01-05 01:27:09.063: W/GooglePlayServicesUtil(27226): Google Play Store signature invalid.
01-05 01:27:09.078: W/GooglePlayServicesUtil(27226): Certificate is not yet valid.
01-05 01:27:09.078: W/GooglePlayServicesUtil(27226): Google Play Store signature invalid.
01-05 01:27:09.078: D/AndroidRuntime(27226): Shutting down VM
01-05 01:27:09.078: W/dalvikvm(27226): threadid=1: thread exiting with uncaught exception (group=0x40c4f1f8)
01-05 01:27:09.083: E/AndroidRuntime(27226): FATAL EXCEPTION: main
01-05 01:27:09.083: E/AndroidRuntime(27226): java.lang.RuntimeException: Unable to start activity ComponentInfo{pl.mg6.android.maps.extensions.demo/pl.mg6.android.maps.extensions.demo.DemoActivity}: java.lang.NullPointerException
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.app.ActivityThread.access$600(ActivityThread.java:127)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.os.Handler.dispatchMessage(Handler.java:99)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.os.Looper.loop(Looper.java:137)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.app.ActivityThread.main(ActivityThread.java:4511)
01-05 01:27:09.083: E/AndroidRuntime(27226): at java.lang.reflect.Method.invokeNative(Native Method)
01-05 01:27:09.083: E/AndroidRuntime(27226): at java.lang.reflect.Method.invoke(Method.java:511)
01-05 01:27:09.083: E/AndroidRuntime(27226): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
01-05 01:27:09.083: E/AndroidRuntime(27226): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
01-05 01:27:09.083: E/AndroidRuntime(27226): at dalvik.system.NativeStart.main(Native Method)
01-05 01:27:09.083: E/AndroidRuntime(27226): Caused by: java.lang.NullPointerException
01-05 01:27:09.083: E/AndroidRuntime(27226): at pl.mg6.android.maps.extensions.demo.DemoActivity.addCircles(DemoActivity.java:220)
01-05 01:27:09.083: E/AndroidRuntime(27226): at pl.mg6.android.maps.extensions.demo.DemoActivity.onCreate(DemoActivity.java:84)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.app.Activity.performCreate(Activity.java:4470)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1052)
01-05 01:27:09.083: E/AndroidRuntime(27226): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
01-05 01:27:09.083: E/AndroidRuntime(27226): ... 11 more