如果整个程序都要横屏，plist中修改下最省事。

	<key>UISupportedInterfaceOrientations</key>
	<array>
		<string>UIInterfaceOrientationLandscapeLeft</string>
	</array>

或者代码中viewcontroller加，

- (BOOL)shouldAutorotate
{
    return NO;
}

- (NSUInteger)supportedInterfaceOrientations
{
    return UIInterfaceOrientationMaskLandscapeRight;
}

- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation
{
    return UIInterfaceOrientationLandscapeRight;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationLandscapeRight);
}