在UITableView中選擇第一行作爲默認值

Question

我有一個基於視圖的應用程序，我將一個tableview作爲子視圖添加到主視圖。我已採取UITableViewDelegate響應表方法。一切工作正常，但我想選擇第一行或UITableView作爲默認選定（突出顯示）。

請幫助我，我需要什麼代碼以及需要放在哪裏。

Answer 1

我們根據它是否是第一個細胞......中間細胞或最後一個細胞，爲細胞使用自定義背景圖像。這樣我們就可以在整個桌子上看到一個很好的圓角。當該行被選中時，它會交換出一個漂亮的「突出顯示」單元格，以便用戶反饋他們已選擇一個單元格。

UIImage *rowBackground; 
UIImage *selectionBackground; 
NSInteger sectionRows = [tableView numberOfRowsInSection:[indexPath section]]; 
NSInteger row = [indexPath row]; 

if (row == 0 && row == sectionRows - 1) 
{ 
    rowBackground = [UIImage imageNamed:@"topAndBottomRow.png"]; 
    selectionBackground = [UIImage imageNamed:@"topAndBottomRowSelected.png"]; 
} 
else if (row == 0) 
{ 
    rowBackground = [UIImage imageNamed:@"topRow.png"]; 
    selectionBackground = [UIImage imageNamed:@"topRowSelected.png"]; 
} 
else if (row == sectionRows - 1) 
{ 
    rowBackground = [UIImage imageNamed:@"bottomRow.png"]; 
    selectionBackground = [UIImage imageNamed:@"bottomRowSelected.png"]; 
} 
else 
{ 
    rowBackground = [UIImage imageNamed:@"middleRow.png"]; 
    selectionBackground = [UIImage imageNamed:@"middleRowSelected.png"]; 
} 


((UIImageView *)cell.backgroundView).image = rowBackground; 
((UIImageView *)cell.selectedBackgroundView).image = selectionBackground; 

如果您希望只創建第一個單元格，即位於indexPath.row == 0的單元格，以使用自定義背景。

這是從馬特·加拉格爾的excellent site

Answer 2

派生你可以這樣做：

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    NSIndexPath *ip=[NSIndexPath indexPathForRow:0 inSection:0]; 
    [myTableView selectRowAtIndexPath:ip animated:YES scrollPosition:UITableViewScrollPositionBottom]; 
} 

Answer 3

- (void)viewDidAppear:(BOOL)animated { 
    [super viewDidAppear:animated]; 
    NSIndexPath *indexPath=[NSIndexPath indexPathForRow:0 inSection:0]; 
    [myTableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionBottom]; 
} 

在你的代碼，如果你想選擇在默認情況下的任何行用最好的方法，在viewDidAppear中使用。

Answer 4

- (void)viewWillAppear:(BOOL)animated 
    { 

     [super viewWillAppear:animated]; 

    // assuming you had the table view wired to IBOutlet myTableView 

     // and that you wanted to select the first item in the first section 

     [myTableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] animated:NO scrollPosition:0]; 
    } 

Answer 5

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    self.detailViewController = (DetailViewController *)[[self.splitViewController.viewControllers lastObject] topViewController]; 

    if([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad){ 
     NSIndexPath* indexPath = [NSIndexPath indexPathForRow:0 inSection:0]; 
     [self.tableView selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionTop]; 
     [self tableView:self.tableView didSelectRowAtIndexPath:indexPath]; 
    } 
} 

Answer 6

下面介紹如何在雨燕1.2做到這一點：

override func viewWillAppear(animated: Bool) { 
    let firstIndexPath = NSIndexPath(forRow: 0, inSection: 0) 
    self.tableView.selectRowAtIndexPath(firstIndexPath, animated: true, scrollPosition: .Top) 
} 

Answer 7

，只選擇第一個單元格的第一次正裝表，人們可能會認爲使用viewDidLoad是正確的地方但是，在執行時，表沒有加載它的內容，所以它不會工作（並且可能會使應用程序崩潰，因爲NSIndexPath將指向不存在的單元）。

解決方法是使用一個變量，該變量指示表之前已加載並相應地完成工作。

@implementation MyClass { 
    BOOL _tableHasBeenShownAtLeastOnce; 
} 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    _tableHasBeenShownAtLeastOnce = NO; // Only on first run 
} 

- (void)viewDidAppear:(BOOL)animated 
{ 
    [super viewDidAppear:animated]; 

    if (! _tableHasBeenShownAtLeastOnce) 
    { 
     _tableHasBeenShownAtLeastOnce = YES; 
     BOOL animationEnabledForInitialFirstRowSelect = YES; // Whether to animate the selection of the first row or not... in viewDidAppear:, it should be YES (to "smooth" it). If you use this same technique in viewWillAppear: then "YES" has no point, since the view hasn't appeared yet. 
     NSIndexPath *indexPathForFirstRow = [NSIndexPath indexPathForRow:0 inSection: 0]; 

     [self.tableView selectRowAtIndexPath:indexPathForFirstRow animated:animationEnabledForInitialFirstRowSelect scrollPosition:UITableViewScrollPositionTop]; 
    } 
} 

/* More Objective-C... */ 

@end 

Answer 8

SWIT 3.0更新的解決方案

let indexPath = IndexPath(row: 0, section: 0) 
tblView.selectRow(at: indexPath, animated: true, scrollPosition: .bottom) 

Answer 9

這裏是我的SWIFT 3.0解決方案：

var selectedDefaultIndexPath = false 


override func viewDidAppear(_ animated: Bool) { 
    super.viewDidAppear(animated) 

    if dataSource.isEmpty == false, selectedDefaultIndexPath == false { 
     let indexPath = IndexPath(row: 0, section: 0) 
     // if have not this, cell.backgroundView will nil. 
     tableView.selectRow(at: indexPath, animated: false, scrollPosition: .none) 
     // trigger delegate to do something. 
     _ = tableView.delegate?.tableView?(tableView, willSelectRowAt: indexPath) 
     selectedDefaultIndexPath = true 
    } 
} 

func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? { 
    let cell = tableView.cellForRow(at: indexPath) 
    cell?.selectedBackgroundView?.backgroundColor = UIColor(hexString: "#F0F0F0") 

    return indexPath 
}