Android Studio ,Run Configuration Error:Default Activity not found

AndroidManifest.xml配置文件里，没配置。这个是启动应用就会默认启动一个Activity的配置。一般是如下配置

        < activity
            android:name = ".MainActivity"
            android:label = "@string/app_name"  >
            < intent-filter >
                < action  android:name = "android.intent.action.MAIN"  />
                < category  android:name = "android.intent.category.LAUNCHER"  />
            intent-filter >
        activity >