實現效果: 當界面有兩個textField時, 利用return鍵切換光標位置.假如光標當前在第一個textField中, 在點擊return鍵時, 將光標自動定位到第二個textField

第一響應者.png

代碼示例:

#import "ViewController.h"

#第一步: 遵循代理協議(注釋)
@interface ViewController ()<UITextFieldDelegate> 

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
   
    UILabel * userLabel = [[UILabel alloc] initWithFrame:CGRectMake(50, 50, 100, 40)];
    userLabel.text = @"用戶名：";
    userLabel.layer.borderColor = [UIColor colorWithRed:0.833 green:0.853 blue:0.857 alpha:1.000].CGColor;
    userLabel.layer.borderWidth = 1;
    userLabel.layer.cornerRadius = 8;
    userLabel.layer.masksToBounds = YES;
    userLabel.backgroundColor = [UIColor colorWithRed:0.726 green:1.000 blue:0.707 alpha:0.741];
    userLabel.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:userLabel];
    
    
    UILabel * passwordLabel = [[UILabel alloc] initWithFrame:CGRectMake(50, 150, 100,40)];
    passwordLabel.backgroundColor = [UIColor colorWithRed:0.726 green:1.000 blue:0.707 alpha:0.741];
    passwordLabel.textAlignment = NSTextAlignmentCenter;
    passwordLabel.text = @"密   碼：";
    passwordLabel.layer.borderColor = [UIColor colorWithRed:0.833 green:0.853 blue:0.857 alpha:1.000].CGColor;
    passwordLabel.layer.borderWidth = 1;
    passwordLabel.layer.cornerRadius = 8;
    passwordLabel.layer.masksToBounds = YES;
    [self.view addSubview:passwordLabel];
    
    
    UITextField * userTextField = [[UITextField alloc] initWithFrame:CGRectMake(180, 50, 200, 40)];
    userTextField.backgroundColor = [UIColor colorWithRed:0.580 green:0.824 blue:0.529 alpha:1.000];
    userTextField.placeholder = @"請輸入用戶名：";
    [self.view addSubview:userTextField];
    userTextField.tag = 1000;
    
    
    UITextField * passwordTextField = [[UITextField alloc] initWithFrame:CGRectMake(180, 150, 200, 40)];
    passwordTextField.backgroundColor = [UIColor colorWithRed:0.580 green:0.824 blue:0.529 alpha:1.000];
    passwordTextField.placeholder = @"請輸入密碼：";

    [self.view addSubview:passwordTextField];
    passwordTextField.tag = 1001;
    
   #第二步: 設置代理
    userTextField.delegate = self;
    passwordTextField.delegate = self;
}

#第三步: 實現代理方法
- (BOOL)textFieldShouldReturn:(UITextField *)textField{
    
    //獲取當前控制器的第二個textField
    UITextField *textf = [self.view viewWithTag:1001];
    //判斷當前選擇的如果是第一個
    if (textField.tag == 1000) {
        //再按return鍵時, 指定第二個為第一響應者
        [textf becomeFirstResponder];
    }
    
    //判斷當前選擇的是第二個, 則釋放第一響應者
    [textField resignFirstResponder];
    
    return YES;
}

@end```