Estava fazendo a aula 4 e quando fui testar o aplicativo não abre, aparece escrito isso na parte de erro, se precisarem de mais informações só pedir.
insira seu código aqui09-08 21:28:47.552 2556-2556/br.com.alura.agenda E/AndroidRuntime: FATAL EXCEPTION: main
Process: br.com.alura.agenda, PID: 2556
java.lang.RuntimeException: Unable to start activity ComponentInfo{br.com.alura.agenda/br.com.alura.agenda.ListaAlunosActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatButton cannot be cast to android.widget.ListView
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatButton cannot be cast to android.widget.ListView
at br.com.alura.agenda.ListaAlunosActivity.onCreate(ListaAlunosActivity.java:19)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
