看上去这样已经完美实现了输入框随键盘自动上移，我们也可以喝杯茶稍微休息一下了。没错，在iOS 8及之后的系统中，确实可以正常的工作，然而如果你的应用需要适配iOS 7并且要支持横屏，那么上面的方式在iOS7上，并不能按照我们的期望正确移动。
原因：在ios7上，键盘的frame，系统是按照竖屏状态下window坐标系来计算的，并不考虑旋转的因素，因此在横屏下得到的键盘frame是错误的。受此影响的还有横屏时获取屏幕宽高[UIScreen mainScreen].bounds，也会有这样的问题。这种情况我们不仅无法正确得到键盘的frame，而且输入框相对于window的坐标计算结果也是错误的。
因此在ios7上，键盘上端的Y坐标以及输入框下端相对于window的Y坐标需要单独处理。键盘上端的Y坐标可以通过屏幕高度减键盘高度得到。我们通过下面的方法获取键盘上端的Y坐标。
- (CGFloat)getKeyboardY:(NSDictionary *)userInfo
{
CGFloat screenHeight;
CGFloat keyboardY = 0;
CGFloat keyboardHeight = 0;
UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
if (( [[[UIDevice currentDevice] systemVersion] floatValue]<8) && UIInterfaceOrientationIsLandscape(orientation))
{
screenHeight = [[UIScreen mainScreen] bounds].size.width;
keyboardHeight = [userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue].size.width;
keyboardY = screenHeight - keyboardHeight;
}
else if (( [[[UIDevice currentDevice] systemVersion] floatValue]<8) && UIInterfaceOrientationIsPortrait(orientation)) {
screenHeight = [[UIScreen mainScreen] bounds].size.height;
keyboardHeight = [userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue].size.height;
keyboardY = screenHeight - keyboardHeight;
}
else {
keyboardY = [userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue].origin.y;
}
return keyboardY;
}
输入框下端相对于window的坐标如何计算呢？我们首先获得的其实是基于竖屏状态下坐标系中的Y值，而我们期望的是横屏下得到横屏状态下坐标系中的Y值，根据两个坐标系的关系，可以将第一次转换得到的坐标再做一次转换，计算得出横屏坐标系下的Y坐标值。我们通过下面的方法获取输入框下端的Y坐标。
- (CGPoint)getViewOriginPointToWindow:(UIView *)view
{
CGPoint origin;
if ([[[UIDevice currentDevice] systemVersion] floatValue] < 8) {
CGPoint focusViewPoint = [view convertPoint:CGPointZero toView:nil];
UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
if (orientation == UIInterfaceOrientationLandscapeLeft) {
origin.y = focusViewPoint.x;
origin.x = [[[UIApplication sharedApplication] delegate] window].bounds.size.height - focusViewPoint.y;
}
else if (orientation == UIInterfaceOrientationLandscapeRight) {
origin.y = [[[UIApplication sharedApplication] delegate] window].bounds.size.width - focusViewPoint.x;
origin.x = focusViewPoint.y;
}
else if (orientation == UIInterfaceOrientationPortraitUpsideDown) {
origin.y = [[[UIApplication sharedApplication] delegate] window].bounds.size.height - focusViewPoint.y;
origin.x = [[[UIApplication sharedApplication] delegate] window].bounds.size.width - focusViewPoint.x;
}
else {
origin = focusViewPoint;
}
}
else {
CGRect rect = [view convertRect:view.bounds toView:[[[UIApplication sharedApplication] delegate] window]];
origin = rect.origin;
}
return origin;
}
