一般在AndroidManifest.xml文件中都沒有使用到android:configChanges="keyboardHidden|orientation"配置，當然還是很有用的。
就是如果配置了這個屬性，當我們橫豎屏切換的時候會直接調用onCreate方法中的onConfigurationChanged方法，而不會重新執行onCreate方法，那當然如果不配置這個屬性的話就會重新調用onCreate方法了
android:configChanges=["mcc", "mnc", "locale",
"touchscreen", "keyboard", "keyboardHidden",
"navigation", "screenLayout", "fontScale", "uiMode",
"orientation", "screenSize", "smallestScreenSize"]
mcc:The IMSI mobile country code (MCC) has changed — a SIM has been detected and updated the MCC.
IMSI(國際移動用戶識別碼)發生改變，檢測到SIM卡，或者更新MCC
mnc:The IMSI mobile network code (MNC) has changed — a SIM has been detected and updated the MNC.
IMSI網絡發生改變,檢測到SIM卡，或者更新MCC
其中mcc和mnc理論上不可能發生變化
locale:The locale has changed — the user has selected a new language that text should be displayed in.
語言發生改變，用戶選擇了一個新的語言，文字應該重新顯示
touchscreen:The touchscreen has changed. (This should never normally happen.)
觸摸屏發生改變，這通常是不應該發生的
keyboard:The keyboard type has changed — for example, the user has plugged in an external keyboard.
鍵盤類型發生改變，例如，用戶使用了外部鍵盤
keyboardHidden:The keyboard accessibility has changed — for example, the user has revealed the hardware keyboard.
鍵盤發生改變，例如，用戶使用了硬件鍵盤
navigation:The navigation type (trackball/dpad) has changed. (This should never normally happen.)
導航發生改變，（這通常不應該發生） 舉例：連接藍牙鍵盤，連接後確實導致了navigation的類型發生變化。因爲連接藍牙鍵盤後，我可以使用方向鍵來navigate了
screenLayout：The screen layout has changed — this might be caused by a different display being activated.
屏幕的佈局發生改變，這可能導致激活不同的顯示
fontScale：The font scaling factor has changed — the user has selected a new global font size.
全局字體大小縮放發生改變
orientation：The screen orientation has changed — that is, the user has rotated the device.設備旋轉，橫向顯示和豎向顯示模式切換。
screenSize: 屏幕大小改變了
smallestScreenSize: 屏幕的物理大小改變了，如：連接到一個外部的屏幕上
4.2增加了一個layoutDirection屬性，當改變語言設置後，該屬性也會成newConfig中的一個mask位。所以ActivityManagerService(實際在ActivityStack)在決定是否重啓Activity的時候總是判斷爲重啓。
需要在android:configChanges 中同時添加locale和layoutDirection。
在不退出應用的情況下切換到Settings裏切換語言，發現該Activity還是重啓了。