Question

我试图这样做，当用户第二次点击标签栏项时，它们将自动滚动到当前屏幕的顶部。

我有一个自定义标签栏视图，其中包含以下代码，可在视图之间切换：

- (IBAction)onTabSelectionChange:(id)sender {
    UIButton *btn = (UIButton*)sender;
    previousIndex = currentIndex;
    currentIndex = btn.tag;

    if (btn.tag == previousIndex){
       // This is where the code should probably go?
    } else {
        if (previousIndex != 0){
            UIButton *btnpreviousIndex = (UIButton*)[tabView viewWithTag:previousIndex];

            if (btnpreviousIndex != nil && previousIndex != -1){
                [btnpreviousIndex setSelected:NO];
            }
            [btn setSelected:YES];
        }
    }
    appDelegate.currentTab = currentIndex;

    switch (currentIndex) {
        case TABHOME: {
            UINavigationController *navController = [appDelegate.arrViewControllers objectAtIndex:0];
            navController.navigationBarHidden = YES;
            [navController popToRootViewControllerAnimated:NO];
            [self presentThisView: navController];
        }
            break;
        case TABTIMELINE: {
            UINavigationController *navController = [appDelegate.arrViewControllers objectAtIndex:1];
            [self presentThisView: navController];
        }
            break;
        case TABNOTIFICATION: {
            UINavigationController *navController = [appDelegate.arrViewControllers objectAtIndex:2];
            [self presentThisView: navController];
            break;
        }
        case TABMISCELLANEOUS: {
            UINavigationController *navController = [appDelegate.arrViewControllers objectAtIndex:3];
            [self presentThisView: navController];
            break;
        }
        default:
            break;
    }
}

提前感谢您的帮助！

Answer 1

如果它是滚动视图，那么您可以将此代码放在您指定的位置：

[scrollView setContentOffset:CGPointZero animated:YES];

<强>更新

您需要在当前选项卡索引处访问视图控制器，然后您可以在其中获取collectionView并执行：

[self.collectionView setContentOffset:CGPointMake(0.0f,0.0f)];

你真的应该实现UITabBarControllerDelegate并将当前代码放在方法

中

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController*)viewController {

通过这种方式，您可以了解前一个和所选视图控制器的内容，然后也可以像我建议的那样访问内部的集合视图。

Answer 2

您可以使用此方法滚动到所需的任何collectionview项目

- (void)scrollToItemAtIndexPath:(NSIndexPath *)indexPath 
               atScrollPosition:(UICollectionViewScrollPosition)scrollPosition 
                       animated:(BOOL)animated

或者您也可以使用[collectionView setContentOffset:CGPointZero animated:YES];

如果你想回到收藏的最开头，你可以简单地使用CGPointZero

在第二次单击自定义选项卡栏时滚动到视图顶部：Objective-C

2 个答案: