iPhone开发之Rotation

iPhone或iPad可以支持4种朝向
    UIInterfaceOrientationPortrait
    UIInterfaceOrientationPortraitUpsideDown
    UIInterfaceOrientationLandscapeLeft
    UIInterfaceOrientationLandscapeRight

究竟支持哪几个朝向，由view controller的shouldAutorotateToInterfaceOrientation函数来指定，每当设备的朝向发生变化时，这个方法都会被调用。

对于iPhone程序，应该防止用户在通话时拿倒电话，不支持UIInterfaceOrientationPortraitUpsideDown
因此函数实现为：
- (BOOL)shouldAutorotateToInterfaceOrientation:  (UIInterfaceOrientation) interfaceOrientation {
      return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
对于iPad，应该支持所有的朝向，因此函数实现为
- (BOOL)shouldAutorotateToInterfaceOrientation:  (UIInterfaceOrientation) interfaceOrientation {
      return true；
}

实现对Rotation的支持有三种方法：
1. 设置UI元素的Autosize Attribute，类似于.NET form的dock
2. 重新构造UI元素大小和位置
3. 不同的朝向使用不同的view

使用Autosize Attribute

Inner box中的红色箭头和UI元素的size有关，如果横向的红色的箭头成为实线，则窗口尺寸变化时UI元素的宽度也会变化，如果横向红色箭头为虚线，则窗口宽度变化时UI元素的宽度保持不变。垂直方向同理。
Inner box周围的短线变成实线时，表明UI元素和它所在的view的边缘的距离保持不变。

下图中的UI对象的高度将会随着view的高度而变化，同时UI元素相对于View的上下边距不变

对应的UI设置为

重新构造UI元素的大小和位置

- (void) willAnimateRotationToInterfaceOrientation :  (UIInterfaceOrientation)
interfaceOrientation duration:(NSTimeInterval)duration {
   if (interfaceOrientation == UIInterfaceOrientationPortrait
        || interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown)
  {
      button1.frame = CGRectMake(20, 20, 125, 125);
      button2.frame = CGRectMake(175, 20, 125, 125);
      button3.frame = CGRectMake(20, 168, 125, 125);
      button4.frame = CGRectMake(175, 168, 125, 125);
      button5.frame = CGRectMake(20, 315, 125, 125);
      button6.frame = CGRectMake(175, 315, 125, 125);
   }
   else
   {
      button1.frame = CGRectMake(20, 20, 125, 125);
      button2.frame = CGRectMake(20, 155, 125, 125);
      button3.frame = CGRectMake(177, 20, 125, 125);
      button4.frame = CGRectMake(177, 155, 125, 125);
      button5.frame = CGRectMake(328, 20, 125, 125);
      button6.frame = CGRectMake(328, 155, 125, 125);
   }
}

切换View

为了支持两个View，需要在View controll中生成两套outlet
@interface SwapViewController : UIViewController {
      UIView *landscape;
      UIView *portrait;
      // Foo
      UIButton *landscapeFooButton;
      UIButton *portraitFooButton;
      // Bar
      UIButton *landscapeBarButton;
      UIButton *portraitBarButton;
}
在Interface builder中删除Xcode自动生成的view，从library中拖两个view 到main window上。分别命名为Portrait和Landscape.
选中File’s Owner，Control-drag 到Portrait和Landscape，连接outlet

动态加载view
#define degreesToRadians(x) (M_PI * (x) / 180.0)

- (void) willAnimateRotationToInterfaceOrientation : (UIInterfaceOrientation)
interfaceOrientation duration:(NSTimeInterval)duration {
if (interfaceOrientation == UIInterfaceOrientationPortrait) {
self.view = self.portrait;
self.view.transform = CGAffineTransformIdentity;
self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(0));#define degreesToRadians(x) (M_PI * (x) / 180.0)
self.view.bounds = CGRectMake(0.0, 0.0, 320.0, 460.0);
}
else if (interfaceOrientation == UIInterfaceOrientationLandscapeLeft) {
self.view = self.landscape;
self.view.transform = CGAffineTransformIdentity;
self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(-90));
self.view.bounds = CGRectMake(0.0, 0.0, 480.0, 300.0);
}
else if (interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown) {
self.view = self.portrait;
self.view.transform = CGAffineTransformIdentity;
self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(180));
self.view.bounds = CGRectMake(0.0, 0.0, 320.0, 460.0);
}
else if (interfaceOrientation == UIInterfaceOrientationLandscapeRight) {
self.view = self.landscape;
self.view.transform = CGAffineTransformIdentity;
self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(90));
self.view.bounds = CGRectMake(0.0, 0.0, 480.0, 300.0);
}
}

iPhone开发之Rotation