求求各位大神支招，小弟在自己开发一个东西，遇到了一个小问题。
图片说明](https://img-ask.csdn.net/upload/201603/15/1458054689_616589.jpg)
我在自定义view的onDraw里，当条件达到后就开启一个子线程发送消息给主线程，让主线程中的handler接收消息并执行相应的动作，可是在Log的输出下只能输出“子线程，”而没有”handlemessage“，并且异常退出，退出代码如下：
03-15 22:50:34.593: W/dalvikvm(27492): threadid=1: thread exiting with uncaught exception (group=0x41c6ece0)
03-15 22:50:34.593: W/dalvikvm(27492): threadid=1: uncaught exception occurred
03-15 22:50:34.593: W/System.err(27492): java.lang.NullPointerException
03-15 22:50:34.593: W/System.err(27492): at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:4094)
03-15 22:50:34.593: W/System.err(27492): at android.os.Handler.dispatchMessage(Handler.java:110)
03-15 22:50:34.593: W/System.err(27492): at android.os.Looper.loop(Looper.java:193)
03-15 22:50:34.593: W/System.err(27492): at android.app.ActivityThread.main(ActivityThread.java:5348)
03-15 22:50:34.593: W/System.err(27492): at java.lang.reflect.Method.invokeNative(Native Method)
03-15 22:50:34.593: W/System.err(27492): at java.lang.reflect.Method.invoke(Method.java:515)
03-15 22:50:34.593: W/System.err(27492): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829)
03-15 22:50:34.594: W/System.err(27492): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645)
03-15 22:50:34.594: W/System.err(27492): at dalvik.system.NativeStart.main(Native Method)
03-15 22:50:34.594: W/dalvikvm(27492): threadid=1: calling UncaughtExceptionHandler
03-15 22:50:34.594: I/dalvikvm(27492): +++ calling Ljava/lang/ThreadGroup;.uncaughtException
03-15 22:50:34.594: D/dalvikvm(27492): threadid=11: bye!
03-15 22:50:34.595: E/AndroidRuntime(27492): FATAL EXCEPTION: main
03-15 22:50:34.595: E/AndroidRuntime(27492): Process: com.example.wyccustomview3, PID: 27492
03-15 22:50:34.595: E/AndroidRuntime(27492): java.lang.NullPointerException
03-15 22:50:34.595: E/AndroidRuntime(27492): at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:4094)
03-15 22:50:34.595: E/AndroidRuntime(27492): at android.os.Handler.dispatchMessage(Handler.java:110)
03-15 22:50:34.595: E/AndroidRuntime(27492): at android.os.Looper.loop(Looper.java:193)
03-15 22:50:34.595: E/AndroidRuntime(27492): at android.app.ActivityThread.main(ActivityThread.java:5348)
03-15 22:50:34.595: E/AndroidRuntime(27492): at java.lang.reflect.Method.invokeNative(Native Method)
03-15 22:50:34.595: E/AndroidRuntime(27492): at java.lang.reflect.Method.invoke(Method.java:515)
03-15 22:50:34.595: E/AndroidRuntime(27492): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829)
03-15 22:50:34.595: E/AndroidRuntime(27492): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645)
03-15 22:50:34.595: E/AndroidRuntime(27492): at dalvik.system.NativeStart.main(Native Method)
