ios - 如何在 iOS 中为自定义键盘制作删除按钮？

Question

我在 Xcode 中制作了一个自定义键盘。它具有普通四功能计算器的所有按键。目前，这是我用来制作计算器类型的方法。它获取被按下按钮的标题并将其添加到字符串 display.text 的末尾。这是我用来让键盘向显示器添加数字的代码。如何从显示屏上删除数字？我可以添加此代码还是需要完全更改它？

-(IBAction)digitPressed:(UIButton *)sender{
    NSString *digit = [sender currentTitle]; //take the title of the button being pressed

if (display.text==nil){ //if there's no text in the display
    NSString *newText = [NSString stringWithFormat:@"%@", digit]; //create a string out of the title of the button being pressed
    display.text = newText; //set the display equal to that string
} else {
    NSString *newText = [NSString stringWithFormat:@"%@%@", display.text, digit]; //add the title of the pressed button to the string we already have
    display.text = newText; //set it as the display text
}
}

Answer 1

你可以用这个

-(IBAction)digitPressed:(UIButton *)sender
{
    NSString *digit = [sender currentTitle];
    display.text=[display.text stringByAppendingString:digit];
}

-(IBAction)deletePressed:(UIButton *)sender
{
    if ( [display.text length] > 0)
        display.text = [display.text substringToIndex:[display.text length] - 1];
}

或者你也可以用它来删除最后一个字符

[myString deleteCharactersInRange:NSMakeRange([myString length]-1, 1)];