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
我做的东西里面还用到了去掉标题栏。
我也贴出来
requestWindowFeature(Window.FEATURE_NO_TITLE);

垂直居中：

android:layout_centerVertical="true"

水平居中：

android:layout_centerHorizontal="true"

1.hideStatusbarAndTitlebar()隐藏statusbar和titlebar.

private void hideStatusbarAndTitlebar() {
final Window win = getWindow();
// No Statusbar
win.setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
// No Titlebar
requestWindowFeature(Window.FEATURE_NO_TITLE);
}