在android开发中使用ImageView实现视频显示时出现如下报错：

java.lang.NullPointerException: Attempt to read from field 'android.widget.ImageView com.example.smartdoor.ui.SmartDoorActivity.video' on a null object reference
       at com.example.smartdoor.ui.SmartDoorActivity.access$500(SmartDoorActivity.java:49)
       at com.example.smartdoor.ui.SmartDoorActivity$6.handleMessage(SmartDoorActivity.java:353)
       at android.os.Handler.dispatchMessage(Handler.java:107)
       at android.os.Looper.loop(Looper.java:213)
       at android.app.ActivityThread.main(ActivityThread.java:8169)
       at java.lang.reflect.Method.invoke(Native Method)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1101)