Question

＆＃13;

@interface ViewController ()

@property (nonatomic, readwrite) BOOL thirdCellVisible;
@property (nonatomic, strong) NSIndexPath *thirdCellIndexPath;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.thirdCellIndexPath = [NSIndexPath indexPathForRow:2 inSection:0];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return 2 + self.thirdCellVisible;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row == self.thirdCellIndexPath.row)
    {
        return 100.0f;
    }

    return 44.0f;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [tableView deselectRowAtIndexPath:indexPath animated:NO];

    if (indexPath.row == 1)
    {
        if (self.thirdCellVisible)
        {
            self.thirdCellVisible = !self.thirdCellVisible;
            [tableView deleteRowsAtIndexPaths:@[self.thirdCellIndexPath]
                         withRowAnimation:UITableViewRowAnimationTop];
        }
        else
        {
            self.thirdCellVisible = !self.thirdCellVisible;
            [tableView insertRowsAtIndexPaths:@[self.thirdCellIndexPath]
                         withRowAnimation:UITableViewRowAnimationTop];
        }
    }
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellId = @"id";

    UITableViewCell *cell = [tableView dequeueReusableHeaderFooterViewWithIdentifier:cellId];

    if(cell == nil)
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellId];
    }

    NSString *cellTitle = [NSString stringWithFormat:@"Cell %ld", (long)indexPath.row];

    cell.textLabel.text = cellTitle;

    if(indexPath.row == 2)
        cell.backgroundColor = [UIColor yellowColor];

    else
        cell.backgroundColor = [UIColor clearColor];

    return cell;
}

@end

＆＃13;

您好，上面是我的代码。

我特意将它设为int x，y，z来测试程序。

当我输入例如（运行程序时）：$ x = 1,1,3 $它总是回答答案！这是为什么？

Answer 1

这是Java的整数除法的示例，它必须始终返回另一个整数。它会截断任何小数结果。即使将结果分配给double，也会发生这种情况。

在分割为强制浮点除法时使用double字面值。

double t = (x+y+z)/3.0;

为什么平均值不是双倍的？

1 个答案: