getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);//设置成全屏模式  
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);//强制为横屏  
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);//竖屏

在activity里设置android:screenOrientation的值。
android:screenOrientation的属性有以下值：
unspecified(默认值，由系统判断状态自动切换),The default value. The system chooses the orientation. The policy it uses, and therefore the choices made in specific contexts, may differ from device to device.
landscape,横屏
portrait,竖屏
user(用户当前设置的orientation值),The user's current preferred orientation.
behind(下一个要显示的Activity的orientation值),The same orientation as the activity that's immediately beneath it in the activity stack.
sensor(传感器的方向),The orientation determined by a physical orientation sensor. The orientation of the display depends on how the user is holding the device; it changes when the user rotates the device.
nosensor(不使用传感器，这个效果差不多等于unspecified).An orientation determined without reference to a physical orientation sensor. The sensor is ignored, so the display will not rotate based on how the user moves the device. Except for this distinction, the system chooses the orientation using the same policy as for the "unspecified" setting.