如何使 UIButton 在选定的 UITextField 中插入负号

Question

我正在 SWIFT 中为 iOS8 创建一个应用程序，它要求用户通过按 UIButton 输入负号。我正在使用的键盘是DecimalPad，它没有该选项。我有多个按钮需要使用的文本字段。例如，如果选择了 UITextField 并且用户按下"-"按钮，则将在该文本字段中插入"-"。我在UIButton知道正在选择哪个UITextField时遇到问题。

任何帮助将不胜感激。

谢谢

Answer 1

@property (weak, nonatomic) IBOutlet UIButton *button;
@property (strong, nonatomic) UITextField *selectedTextField;
- (void) viewDidLoad{
    [super viewDidLoad];
    [self.button addTarget:self action:@selector(buttonTapped:) forControlEvents:UIControlEventTouchUpInside];
}
- (void) buttonTapped: (UIButton *) sender{
    self.selectedTextField.text = [NSString stringWithFormat:@"-%@",self.selectedTextField.text];
}
//Make sure you set the delegate of every UITextField to this UIViewController.  
//Also make sure you state that this UIViewController implements the UITextFieldDelegate protocol by inserting <UITextFieldDelegate> in the interface header.
-(void)textFieldDidBeginEditing:(UITextField *)sender{  
    self.selectedTextField = sender; 
}

Answer 2

此解决方案利用insertText:允许您在当前光标位置的任何位置插入"-"。注意：确保将UITextField委托设置为自身，以利用textFieldDidBeginEditing:和textFieldDidEndEditing:委托方法。

class ViewController: UIViewController, UITextFieldDelegate {
    var selectedTextField:UITextField?
    @IBAction func negativeButtonPress(sender: UIButton) {
        // If a text field stored in selectedTextField
        // insert "-" at the cursor position 
        if let field:UITextField = selectedTextField {
            field.insertText("-")
        }
    }
    // Sets selectedTextField to the current text field
    // when the text field begins editing
    func textFieldDidBeginEditing(textField: UITextField) {
        selectedTextField = textField
    }
    // Sets selectedTextField to the nil
    // when the text field ends editing
    func textFieldDidEndEditing(textField: UITextField) {
        selectedTextField = nil
    }
}