How me make the UIButton's alpha less than 1?

Question

Right now if I add a button in Interface Builder and then in view attribute of "button attributes", i can find a place to adjust the alpha, but the problem is that when i adjust the alpha, the whole button's alpha changes, even the alpha of the label changes.
But what i want is that I want to have label's alpha not changed but the other places of the button's alpha changed, is there a way to do it?

Answer 1

Ok. Here's a custom subclass of UIButton that might do what you want. It's based on the example of a label over a button I described in my last post. But instead of a label this class is built from a Custom type button with a Rounded Rect type button under it:
// MyButton.h
#import <UIKit/UIKit.h>
#define kNormalAlpha 0.5 // default normal background alpha
#define kHiliteAlpha 0.8 // default hilighted background alpha
@interface MyButton : UIButton {
UIButton *bgButton; // used only to draw the background
CGFloat bgNormalAlpha; // alpha of background for normal state
CGFloat bgHiliteAlpha; // alpha of background for highlighted state
@property (nonatomic, retain) UIButton *bgButton;
- (void)setBgAlpha:(CGFloat)value forState:(UIControlState)state;
@end
// MyButton.m
#import "MyButton.h"
@implementation MyButton
@synthesize bgButton;
- (void)setBgAlpha:(CGFloat)value forState:(UIControlState)state {
if (state == UIControlStateHighlighted)
bgHiliteAlpha = value;
else
bgNormalAlpha = value;
bgButton.alpha = self.highlighted ? bgHiliteAlpha : bgNormalAlpha;
// override setter so background can track current state
- (void)setHighlighted:(BOOL)highlighted {
// NSLog(@"%s: %d", _func_, highlighted);
[super setHighlighted:highlighted];
[bgButton setHighlighted:highlighted];
bgButton.alpha = highlighted ? bgHiliteAlpha : bgNormalAlpha;
- (void)myInit {
// set default alpha values
bgNormalAlpha = kNormalAlpha;
bgHiliteAlpha = kHiliteAlpha;
// make background button
self.bgButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
bgButton.frame = self.frame;
bgButton.autoresizingMask = self.autoresizingMask;
bgButton.alpha = bgNormalAlpha;
- (void)didMoveToSuperview {
NSLog(@"%s", _func_);
[super didMoveToSuperview];
[self.superview insertSubview:bgButton belowSubview:self];
- (id)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
NSLog(@"%s: buttonType=%d", _func_, self.buttonType);
[self myInit];
return self;
- (id)initWithCoder:(NSCoder*)aDecoder {
if (self = [super initWithCoder:aDecoder]) {
NSLog(@"%s: buttonType=%d", _func_, self.buttonType);
[self myInit];
return self;
- (void)dealloc {
[bgButton release];
[super dealloc];
@end
To use this class, just add the above @interface and @implementation to your project (File->New File..., name the files "MyButton", then replace the contents by pasting directly from this forum page). You should then be able to customize any UIButton object in IB by selecting the button and setting its Class to MyButton in the Identity Inspector. To create an instance of MyButton in code, use initWithFrame.
- Ray