Android - มือใหม่!!ขอถามเรื่อง Titlebar พอสร้างแล้วมันค้าง!!!!!!

12-26 10:07:30.301  25373-25373/com.example.thammachet.test21231 D/ActivityThread﹕ handleBindApplication:com.example.thammachet.test21231
12-26 10:07:30.311  25373-25373/com.example.thammachet.test21231 D/ActivityThread﹕ setTargetHeapUtilization:0.75
12-26 10:07:30.311  25373-25373/com.example.thammachet.test21231 D/ActivityThread﹕ setTargetHeapMinFree:2097152
12-26 10:07:30.461  25373-25373/com.example.thammachet.test21231 D/AndroidRuntime﹕ Shutting down VM
12-26 10:07:30.461  25373-25373/com.example.thammachet.test21231 W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4174ace0)
12-26 10:07:30.471  25373-25373/com.example.thammachet.test21231 E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.thammachet.test21231, PID: 25373
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.thammachet.test21231/com.example.thammachet.test21231.MainActivity}: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2212)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5146)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
            at android.support.v7.app.ActionBarActivityDelegate.onCreate(ActionBarActivityDelegate.java:151)
            at android.support.v7.app.ActionBarActivityDelegateBase.onCreate(ActionBarActivityDelegateBase.java:138)
            at android.support.v7.app.ActionBarActivity.onCreate(ActionBarActivity.java:123)
            at com.example.thammachet.test21231.MainActivity.onCreate(MainActivity.java:13)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5146)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
            at dalvik.system.NativeStart.main(Native Method)