Android 问题，求大神解决！

06-29 10:49:34.195 23540-23540/com.ziyeyanhuo.assetmanagement E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.ziyeyanhuo.assetmanagement, PID: 23540
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ziyeyanhuo.assetmanagement/com.ziyeyanhuo.assetmanagement.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.DrawerLayout.setDrawerListener(android.support.v4.widget.DrawerLayout$DrawerListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2466)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2528)
at android.app.ActivityThread.access$800(ActivityThread.java:169)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5552)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.DrawerLayout.setDrawerListener(android.support.v4.widget.DrawerLayout$DrawerListener)' on a null object reference
at com.ziyeyanhuo.assetmanagement.MainActivity.onCreate(MainActivity.java:54)
at android.app.Activity.performCreate(Activity.java:5975)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1111)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2419)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2528) 
at android.app.ActivityThread.access$800(ActivityThread.java:169) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421) 
at android.os.Handler.dispatchMessage(Handler.java:111) 
at android.os.Looper.loop(Looper.java:194) 
at android.app.ActivityThread.main(ActivityThread.java:5552) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)