find crash

[liuwei1993]

Process: com.flipboard.bottomsheet.sample, PID: 22228
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.flipboard.bottomsheet.sample/com.flipboard.bottomsheet.sample.TestActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setLayerType(int, android.graphics.Paint)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2876)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2941)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1649)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:203)
at android.app.ActivityThread.main(ActivityThread.java:6475)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1134)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:995)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setLayerType(int, android.graphics.Paint)' on a null object reference
at com.flipboard.bottomsheet.BottomSheetLayout.setSheetLayerTypeIfEnabled(BottomSheetLayout.java:470)
at com.flipboard.bottomsheet.BottomSheetLayout.expandSheet(BottomSheetLayout.java:507)
at com.flipboard.bottomsheet.sample.TestActivity.onCreate(TestActivity.java:22)
at android.app.Activity.performCreate(Activity.java:6765)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1122)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2829)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2941) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1649) 
at android.os.Handler.dispatchMessage(Handler.java:110) 
at android.os.Looper.loop(Looper.java:203) 
at android.app.ActivityThread.main(ActivityThread.java:6475) 
at java.lang.reflect.Method.invoke(Native Method)