小编Sad*_*han的帖子

合并两个 androidStudio 项目后，我遇到了这个错误，应用程序初始化为飞溅，并且显示和运行良好。然后当尝试访问 activity_main.xml 时，应用程序崩溃。错误是：

FATAL EXCEPTION: main
              Process: eu.siacs.conversations, PID: 16604
              java.lang.RuntimeException: Unable to start activity ComponentInfo{eu.siacs.conversations/eu.siacs.conversations.ui.MainActivity}: java.lang.ClassCastException: android.support.constraint.ConstraintLayout cannot be cast to android.support.v4.widget.DrawerLayout
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2726)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2787)
                  at android.app.ActivityThread.-wrap12(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1504)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6247)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:872)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:762)
               Caused by: java.lang.ClassCastException: android.support.constraint.ConstraintLayout cannot be cast to android.support.v4.widget.DrawerLayout
                  at eu.siacs.conversations.ui.MainActivity.onCreate(MainActivity.java:96)
                  at android.app.Activity.performCreate(Activity.java:6757)
                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2679)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2787) 
                  at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1504) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6247) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:872) …