ios - 从另一个方法 objective-c 中更新变量

Question

我是 Objective C、XCode iOS 的新手，所以我从一个简单的计数器应用开始。

我已经设置了基础知识(增加按下按钮的分数)但我似乎无法在每次按下按钮时更新 UILabel 文本，即每次我增加 currentScore它不会更新 UILabel 文本

中的 currentScore 变量

#import "JPViewController.h"

@implementation JPViewController

int currentScore;

- (void)viewDidLoad
{
    
    [super viewDidLoad];
    
    //Init currentScore
    currentScore = 0;
    NSLog(@"Your score is %d", currentScore);
    
    //Points text label
    
    UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(100, 100, 290, 400)];
    label.text = [NSString stringWithFormat:@"Your score is: %d", currentScore];
    [label setFont:[UIFont boldSystemFontOfSize:16]];
    //TODO: Position points in centre.
    [self.view addSubview:label];
    
    //Add Points Button
    
    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
    [button setTitle:@"Press Me" forState:UIControlStateNormal];
    [button sizeToFit];
    button.center = CGPointMake(320/2, 60);
    [button addTarget:self action:@selector(buttonPressed:)
     forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
 
}

- (void)buttonPressed:(UIButton *)button {
    NSLog(@"Button Pressed");
    currentScore++;
    NSLog(@"Your score is %d", currentScore);
    //TODO: Update the label with the new currentScore here.
}

Answer 1

要在按钮旁边使用标签，请执行以下操作

1) 给你的标签打标签

 UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(100, 100, 290, 400)];
    label.text = [NSString stringWithFormat:@"Your score is: %d", currentScore];
    [label setFont:[UIFont boldSystemFontOfSize:16]];
    //TODO: Position points in centre.
    [label setTag:1000];//Give tag to your label 
    [self.view addSubview:label];

2) 然后在按钮方法中通过它的标签获取标签

- (void)buttonPressed:(UIButton *)button {
    NSLog(@"Button Pressed");
    currentScore++;
    NSLog(@"Your score is %d", currentScore);
    UILabel *label = (UILabel) [self.view viewWithTag:1000]; // you get your label reference here
    [label setText:[NSString stringWithFormate:%d,currentScore]]; // then store your current score in your lable
    //TODO: Update the label with the new currentScore here.
}

或者这是第二种方法

1) 使您的 UILabel 变量成为全局变量，如下所示

 @implementation JPViewController
    {
          UILabel *label;
    }

2) 在viewDidLoad()中

label = [[UILabel alloc]initWithFrame:CGRectMake(100, 100, 290, 400)];
        label.text = [NSString stringWithFormat:@"Your score is: %d", currentScore];
        [label setFont:[UIFont boldSystemFontOfSize:16]];
        //TODO: Position points in centre.
        [self.view addSubview:label];

3) 在你的按钮事件中

- (void)buttonPressed:(UIButton *)button {
        NSLog(@"Button Pressed");
        currentScore++;
        NSLog(@"Your score is %d", currentScore);
        [label setText:[NSString stringWithFormate:%d,currentScore]]; // then store your current score in your lable
        //TODO: Update the label with the new currentScore here.
    }