如果所有行都有复选标记，则启用一个按钮

Question

我有一个 UITableView，当所有行都有 Checkmark.

时，我需要 启用导航栏按钮

有办法吗？

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    tableData = [NSArray arrayWithObjects:@"1", @"2", @"3", nil];

    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(print_Message)];
    self.navigationItem.rightBarButtonItem.enabled = NO;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"SimpleTableCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    cell.textLabel.text = [tableData objectAtIndex:indexPath.row];

    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{

    NSLog(@"didSelectRow");

    UIAlertView *messageAlert = [[UIAlertView alloc] initWithTitle:@"Row Selected" message:[tableData objectAtIndex:indexPath.row] delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil];

    [messageAlert show];

    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

    if (cell.accessoryType == UITableViewCellAccessoryNone) {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;

    } else {
        cell.accessoryType = UITableViewCellAccessoryNone;
    }

    [tableView deselectRowAtIndexPath:indexPath animated:YES];
}

Answer 1

只要 cellForRowAtIndexPath: 不会在索引路径上被多次调用（例如在滚动、强制重新加载、视图重新出现等情况下），您就可以利用您的 UITableView 的 indexPathsForSelectedRows 来帮助确定是否所有单元格都被选中。

为了让 indexPathsForSelectedRows 正常工作，需要对您的代码进行一些更改。

(1) 在你的 viewDidLoad.

中添加 self.tableView.allowsMultipleSelection = YES;

(2) 在初始代码中，您在方法末尾使用 didSelectRowAtIndexPath: 和 deselectRowAtIndexPath:。相反，使用 didSelectRowAtIndexPath: 和 didDeselectRowAtIndexPath: 以便选择选中标记的行而不选择未选中标记的行。

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    tableData = [NSArray arrayWithObjects:@"1", @"2", @"3", nil];

    self.tableView.allowsMultipleSelection = YES;

    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(print_Message)];
    self.navigationItem.rightBarButtonItem.enabled = NO;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
    cell.accessoryType = UITableViewCellAccessoryCheckmark;

    // If the number of selected index paths = the number of rows,
    // enable the button
    NSArray *selectedIndexPaths = [tableView indexPathsForSelectedRows];
    if (selectedIndexPaths.count == [tableView numberOfRowsInSection:0]) {
        self.navigationItem.rightBarButtonItem.enabled = YES;
    }
}

- (void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
    cell.accessoryType = UITableViewCellAccessoryNone;

    self.navigationItem.rightBarButtonItem.enabled = NO;
}