Question

I want to do a shift key. When I click it, the key will change to other letters. How can I make it bright when clicking this shift button like in iphone ? Can you give some example codes ?

Answer 1

If you’d like a button’s image to change when tapped, and then back, you can use the -[setImage:forState:] method. For this example, imagine yourself having 2 images: image_one.png and image_two.png for the unpressed and pressed images respectively.

Suppose you have a button like so:

UIButton *button = [[UIButton alloc] init];
[button setFrame:CGRectMake(0, 0, 100, 44)];
[button setImage:[UIImage imageNamed:@"image_one.png"] forState:UIControlStateNormal];
[[self view] addSubview:button];

You can add a target and action that will change the image back and forth. To see which image it is currently, I’d use the tag property.

[button setTag:0]; // initial, non pressed button tag, for this example
[button addTarget:self action:@selector(swapImage:) forControlEvents:UIControlEventTouchUpInside];

And have something like the following in the setImage method:

-(void)swapImage:(UIButton *)sender {

    if ([sender tag] == 0) {

        [sender setTag:1]; // pressed tag, for example
        [sender setImage:[UIImage imageNamed:@"image_two.png"] forState:UIControlStateNormal];

    } else {

        [sender setTag:0]; // non-pressed tag, for example
        [sender setImage:[UIImage imageNamed:@"image_one.png"] forState:UIControlStateNormal];

    }

}

When you first tap the button, it selects. Tapping it another time will unselect it – just like the keyboard’s shift button.