iOS 获取 UITabViewController 和 UINavigationController 的图标位置

这些图标是放在 UITabBar 和 UINavigationBar 里的。所以只要遍历它们的 subViews，找到类型是 UIButton 的就可以了。

所有想获取它们的相对位置很容易。

获取到相对位置之后，根据容器位置进行调整就可以了。

所以 UITabBar 里图标的位置：

CGPoint center = CGPointMake(centerInTab.x + tabBar.frame.origin.x, centerInTab.y + tabBar.frame.origin.y);

UINavigationBar 里图标的位置：

CGPoint center = CGPointMake(point.x + self.navigationController.navigationBar.frame.origin.x, point.y + self.navigationController.navigationBar.frame.origin.y)；

注意：获取位置的这些函数的调用要在 viewDidAppear 之后，否则结果不准确。

获取相对位置的代码：

+ (CGPoint)centerForTabInTabBar:(UITabBar*)tabBar withIndex:(NSUInteger)index
{
    NSMutableArray *tabBarItems = [NSMutableArray arrayWithCapacity:[tabBar.items count]];
    for (UIView *view in tabBar.subviews) {
        if ([view isKindOfClass:NSClassFromString(@"UITabBarButton")] && [view respondsToSelector:@selector(frame)]) {
            // check for the selector -frame to prevent crashes in the very unlikely case that in the future
            // objects thar don't implement -frame can be subViews of an UIView
            [tabBarItems addObject:view];
        }
    }
    if ([tabBarItems count] == ) {
        // no tabBarItems means either no UITabBarButtons were in the subView, or none responded to -frame
        // return CGRectZero to indicate that we couldn't figure out the frame
        return CGPointZero;
    }

    // sort by origin.x of the frame because the items are not necessarily in the correct order
    [tabBarItems sortUsingComparator:^NSComparisonResult(UIView *view1, UIView *view2) {
        if (view1.frame.origin.x < view2.frame.origin.x) {
            return NSOrderedAscending;
        }
        if (view1.frame.origin.x > view2.frame.origin.x) {
            return NSOrderedDescending;
        }
        NSAssert(NO, @"%@ and %@ share the same origin.x. This should never happen and indicates a substantial change in the framework that renders this method useless.", view1, view2);
        return NSOrderedSame;
    }];

    CGPoint center = CGPointZero;
    if (index < [tabBarItems count]) {
        // viewController is in a regular tab
        UIView *tabView = tabBarItems[index];
        center = tabView.center;
    }
    else {
        // our target viewController is inside the "more" tab
        UIView *tabView = [tabBarItems lastObject];
        center = tabView.center;
    }
    return center;
}

+ (CGPoint)centerForItemInNavigationBar:(UINavigationBar *)navigationBar withIndex:(NSUInteger)index
{
    NSLog(@"centerForItemInNavigationBar: withIndex:%d",index);
    NSMutableArray *navigationBarItems = [NSMutableArray arrayWithCapacity:[navigationBar.items count]];
    for (UIView *view in navigationBar.subviews) {
        if ([view isKindOfClass:NSClassFromString(@"UIButton")] && [view respondsToSelector:@selector(frame)]) {
            // check for the selector -frame to prevent crashes in the very unlikely case that in the future
            // objects thar don't implement -frame can be subViews of an UIView
            [navigationBarItems addObject:view];
        }
    }
    if ([navigationBarItems count] == ) {
        // no navigationBarItems means either no UIButton were in the subView, or none responded to -frame
        // return CGRectZero to indicate that we couldn't figure out the frame
        return CGPointZero;
    }

    // sort by origin.x of the frame because the items are not necessarily in the correct order
    [navigationBarItems sortUsingComparator:^NSComparisonResult(UIView *view1, UIView *view2) {
        if (view1.frame.origin.x < view2.frame.origin.x) {
            return NSOrderedAscending;
        }
        if (view1.frame.origin.x > view2.frame.origin.x) {
            return NSOrderedDescending;
        }
        NSAssert(NO, @"%@ and %@ share the same origin.x. This should never happen and indicates a substantial change in the framework that renders this method useless.", view1, view2);
        return NSOrderedSame;
    }];

    CGPoint point = CGPointZero;

    UIView *navigationView = navigationBarItems[index];
    NSLog(@"center %f,%f", navigationView.center.x, navigationView.center.y);
    return navigationView.center;
}