android中有这么些个SystemService，挨个儿了解

Service大全

ACCESSIBILITY_SERVICE //加速器

ACCOUNT_SERVICE

ACTIVITY_SERVICE

ALARM_SERVICE

AUDIO_SERVICE

CLIPBOARD_SERVICE

CONNECTIVITY_SERVICE

DEVICE_POLICY_SERVICE

DISPLAY_SERVICE

DOWNLOAD_SERVICE

DROPBOX_SERVICE

INPUT_METHOD_SERVICE

INPUT_SERVICE

KEYGUARD_SERVICE

LAYOUT_INFATER_SERVICE

LOCATION_SERVICE

MEDIA_ROUTER_SERVICE

NFC_SERVICE

NOTIFICATION_SERVICE

NSD_SERVICE

PWOER_SERVICE

SEARCH_SERVICE

SENSOR_SERVICE

STORAGE_SERVICE

TELEPHONY_SERVICE

TEXT_SERVICES_MANAGER_SERVICE

UI_MODE_SERVICE

USB_SERVICE

USER_SERVICE

VIBATOR_SERVICE

WALLPAPER_SERVICE

WIFI_P2P_SERVICE

WIFI_SERVICE

WINDOW_SERVICE

用例：context.getSystemService(Context.CONNECTIVITY_SERVICE)