How can i change the style of UIBarButtonItem in code

Question

I am using UIBarButtonSystemItemPlay to play my audio file and i want to change it's style dynamically when i click it. Is it possible?, if yes, then please help me. This is my code, where _playPause is IBOutlet of UIBarButtonSystemItemPlay. Thanks in advance.

- (IBAction)playPause:(UIBarButtonItem *) sender
{
    if (_playPause.style == UIBarButtonSystemItemPlay)
    {
        [_playPause setStyle:UIBarButtonSystemItemPause];
        [audio play];
    }
    else
    {
        [_playPause setStyle:UIBarButtonSystemItemPlay];
        [audio pause];
    }
}

Answer 1

UIBarButtonSystemItemPlay or UIBarButtonSystemItemPause cannot be retrieved by style property. style is of type UIBarButtonItemStyle.

Check the documentation here.

I suggest to create two different UIBarButtonItem and then enable or disable (for example) them alternately. It is also possible to remove the current visible button and add a new one with a different UIBarButtonSystemItem.

Answer 2

Here's a pretty complete solution for this that I just implemented:

First, define vars to hold both buttons:

@property (weak, nonatomic) IBOutlet UIToolbar *toolbar;
@property (strong, nonatomic) IBOutlet UIBarButtonItem *playButton;
@property (strong, nonatomic) IBOutlet UIBarButtonItem *pauseButton;

(My understanding here is that the toolbar is a weak ref since it is being defined via IB and it has a strong pointer to it, but that the play/pause buttons are strong pointers because we are creating them below. But my fu is a little weak on this front as a fairly newbie, so corrections appreciated.)

Second, in IB create just a play button (no pause button) and tie it to the above playButton var.

Third, set up this method:

- (void) setAsPlaying:(BOOL)isPlaying
{
    self.rootViewController.playing = isPlaying;

    // we need to change which of play/pause buttons are showing, if the one to
    // reverse current action isn't showing
    if ((isPlaying && !self.pauseButton) || (!isPlaying && !self.playButton))
    {
        UIBarButtonItem *buttonToRemove = nil;
        UIBarButtonItem *buttonToAdd = nil;
        if (isPlaying)
        {
            buttonToRemove = self.playButton;
            self.playButton = nil;
            self.pauseButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemPause
                                                                             target:self
                                                                             action:@selector(pauseAudio:)];
            buttonToAdd = self.pauseButton;
        }
        else
        {
            buttonToRemove = self.pauseButton;
            self.pauseButton = nil;
            self.playButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemPlay
                                                                            target:self
                                                                            action:@selector(playAudio:)];
            buttonToAdd = self.playButton;
        }

        // Get the reference to the current toolbar buttons
        NSMutableArray *toolbarButtons = [[self.toolbar items] mutableCopy];

        // Remove a button from the toolbar and add the other one
        if (buttonToRemove)
            [toolbarButtons removeObject:buttonToRemove];
        if (![toolbarButtons containsObject:buttonToAdd])
            [toolbarButtons insertObject:buttonToAdd atIndex:2];    // vary this index to put in diff spots in toolbar

        [self.toolbar setItems:toolbarButtons];
    }
}

Fourth, call setAsPlaying wherever you are going to play or pause mode. For instance:

-(IBAction) playAudio:(id)sender
{
    [self.audioPlayer play];
    [self setAsPlaying:YES];
}

-(IBAction) pauseAudio:(id)sender
{
    [self.audioPlayer pause];
    [self setAsPlaying:NO];
}