iPhone应用程序对设备方向更改的响应

Question

设备如何知道设备方向已更改，然后开始响应？在一个使用opengl的简单应用程序中，当设备方向发生变化时，两个函数将协同工作以在渲染引擎中对此事件做出反应：UpdateAnimation、OnRotate我的问题是，它们是如何被触发的？？

谢谢你的帮助，亚辛

//////////////////////////////////////样本代码

class RenderingEngine1 : public IRenderingEngine {
public:
RenderingEngine1();
void Initialize(int width, int height);
void Render() const;
void UpdateAnimation(float timeStep);
void OnRotate(DeviceOrientation newOrientation);
private:
vector<Vertex> m_cone;
vector<Vertex> m_disk;
Animation m_animation;
GLuint m_framebuffer;
GLuint m_colorRenderbuffer;
GLuint m_depthRenderbuffer;
};

void RenderingEngine1::OnRotate(DeviceOrientation orientation)
{
vec3 direction;
switch (orientation) {
case DeviceOrientationUnknown:
case DeviceOrientationPortrait:
direction = vec3(0, 1, 0);
break;
case DeviceOrientationPortraitUpsideDown:
direction = vec3(0, -1, 0);
break;
case DeviceOrientationFaceDown:
direction = vec3(0, 0, -1);
break;
case DeviceOrientationFaceUp:
direction = vec3(0, 0, 1);
break;
case DeviceOrientationLandscapeLeft:
direction = vec3(+1, 0, 0);
break;
case DeviceOrientationLandscapeRight:
direction = vec3(-1, 0, 0);
break;
}
m_animation.Elapsed = 0;
m_animation.Start = m_animation.Current = m_animation.End;
m_animation.End = Quaternion::CreateFromVectors(vec3(0, 1, 0), direction);
}

void RenderingEngine1::UpdateAnimation(float timeStep)
{
if (m_animation.Current == m_animation.End)
return;
m_animation.Elapsed += timeStep;
if (m_animation.Elapsed >= AnimationDuration) {
m_animation.Current = m_animation.End;
} else {
float mu = m_animation.Elapsed / AnimationDuration;
m_animation.Current = m_animation.Start.Slerp(mu, m_animation.End);
}
}

Answer 1

此处的其他答案指的是接口方向的变化，而我相信您询问的是设备方向的变化（可能会也可能不会影响接口方向）

应用程序中的相关类实例需要启动设备定向通知：

[[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];

然后，它需要设置自己，以便在设备方向发生变化时接收通知：

[[NSNotificationCenter defaultCenter] 
            addObserver:self 
               selector:@selector(didRotate:) 
                   name:UIDeviceOrientationDidChangeNotification 
                 object:nil];

在selector指示的方法中，它可以检查当前方向，因此：

- (void)didRotate:(NSNotification*)notification { 
     UIDeviceOrientation orientation = [UIDevice currentDevice].orientation;
     ...
}

类实例还需要在不再需要设备定向通知时停止这些通知，并将自己作为观察者删除（- dealloc通常是执行此操作的好地方）

[[UIDevice currentDevice] endGeneratingDeviceOrientationNotifications];
[[NSNotificationCenter defaultCenter] removeObserver:self];

Answer 2

-(void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation
{
     //Do what you want here
}

当设备改变方向时调用此方法。。

Answer 3

来源：如何在iOS5中获得默认的LandscapeLeft Orientation

调用下面的方法来检查方向的状态。快乐编码：-）

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
    [self CheckForViewForOrientation:toInterfaceOrientation];
}
- (void) CheckForViewForOrientation:(UIInterfaceOrientation)orientation
{
    if (orientation == UIInterfaceOrientationPortrait || orientation == UIInterfaceOrientationPortraitUpsideDown)
    {
        //portrait view
    }
    else if (orientation == UIInterfaceOrientationLandscapeLeft || orientation == UIInterfaceOrientationLandscapeRight)
    {
        //landscape view
    }
}