如果android模拟器已经启动后，可以使用快捷键F12或Ctrl+F11来切换。当然是用命令行仅仅启动模拟器可以使用参数emulator.exe -skin HVGA-L
来启动。
（还有我发现，我的小键盘锁住的时候，按8然后按7，也横屏了，虽然不知道什么原因，还是在这里补充一下）
需要注意的是，程序会重载onCreate，避免的方法可通过androidmanifest.xml文件中重新定义方向，以及根据Activity的重写onConfigurationChanged(Configuration newConfig)方法来控制。
Activity 的 ConfigChanges 属性
官方解释： 通过设置这个属性可以使Activity捕捉设备状态变化，以下是可以被识别的内容：
CONFIG_FONT_SCALE CONFIG_MCC CONFIG_MNC CONFIG_LOCALE CONFIG_TOUCHSCREEN CONFIG_KEYBOARD CONFIG_NAVIGATION CONFIG_ORIENTATION
设置方法：将下列字段用“|”符号分隔开，例如：“locale|navigation|orientation”
Value
Description
Description
“mcc“
The IMSI mobile country code (MCC) has changed — that is, a SIM hasbeen detected and updated the MCC.移动国家号码，由三位数字组成，每个国家都有自己独立的MCC，可以识别手机用户所属国家。
The IMSI mobile country code (MCC) has changed — that is, a SIM hasbeen detected and updated the MCC.移动国家号码，由三位数字组成，每个国家都有自己独立的MCC，可以识别手机用户所属国家。
“mnc“
The IMSI mobile network code (MNC) has changed — that is, a SIM hasbeen detected and updated the MNC.移动网号，在一个国家或者地区中，用于区分手机用户的服务商。
The IMSI mobile network code (MNC) has changed — that is, a SIM hasbeen detected and updated the MNC.移动网号，在一个国家或者地区中，用于区分手机用户的服务商。
“locale“
The locale has changed — for example, the user has selected a new language that text should be displayed in.用户所在地区发生变化。
The locale has changed — for example, the user has selected a new language that text should be displayed in.用户所在地区发生变化。
“touchscreen“
The touchscreen has changed. (This should never normally happen.)
The touchscreen has changed. (This should never normally happen.)
“keyboard“
The keyboard type has changed — for example, the user has plugged in an external keyboard.键盘模式发生变化，例如：用户接入外部键盘输入。
The keyboard type has changed — for example, the user has plugged in an external keyboard.键盘模式发生变化，例如：用户接入外部键盘输入。
“keyboardHidden“
The keyboard accessibility has changed — for example, the user has slid the keyboard out to expose it.用户打开手机硬件键盘
The keyboard accessibility has changed — for example, the user has slid the keyboard out to expose it.用户打开手机硬件键盘
“navigation“
The navigation type has changed. (This should never normally happen.)
The navigation type has changed. (This should never normally happen.)
“orientation“
The screen orientation has changed — that is, the user has rotated the device.设备旋转，横向显示和竖向显示模式切换。
The screen orientation has changed — that is, the user has rotated the device.设备旋转，横向显示和竖向显示模式切换。
“fontScale“
The font scaling factor has changed — that is, the user has selected a new global font size.全局字体大小缩放发生改变
The font scaling factor has changed — that is, the user has selected a new global font size.全局字体大小缩放发生改变
1、不设置Activity的android:configChanges时，切屏会重新调用各个生命周期，切横屏时会执行一次，切竖屏时会执行一次，网上有的说是，切竖屏会执行两次，我在android2.3的模拟器和2.3手机上都试了，只有一次。但是在android2.2的模拟器上测试了，切竖屏的时候，会执行两次声明周期。
2、设置Activity的android:configChanges="orientation"时，切屏还是会重新调用各个生命周期，切横、竖屏时只会执行一次，而且，切竖屏的时候，最后还会调用onConfigurationChanged 。模拟器会按照以上说的执行，手机的话，不会执行声明周期，只会执行 onConfigurationChanged
3、设置Activity的android:configChanges="orientation|keyboardHidden"时，切屏不会重新调用各个生命周期，只会执行onConfigurationChanged方法