UIButton is not clickable

I searched in other posts, but I could not find a solution.

I have a UIButton that cannot be clicked. When I click, it does not get dark. The problem is not the selection method.

Can someone help me ?! Here is the code:

- (void)drawRect:(CGRect)rect
{

    UIScrollView *scroll = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, 320, 436)];

    UIView *detailsView = [[UIView alloc] init];

// I have other components here and after the UIButton

    UIButton *btnOpenPDF = [UIButton buttonWithType:UIButtonTypeCustom];
    [btnOpenPDF setBackgroundImage:[UIImage imageNamed:@"btnVisualizarPdf"] forState:UIControlStateNormal];
    [btnOpenPDF setFrame:CGRectMake(35, totalHeight, 249, 30)];
    btnOpenPDF.userInteractionEnabled = YES;
    [btnOpenPDF addTarget:self action:@selector(openPdf:) forControlEvents:UIControlEventTouchDown];

    [detailsView addSubview:btnOpenPDF];

    [scroll addSubview:detailsView];

    [self addSubview:scroll];

}

The code above is inside the UIView, which is called through the UIViewController using the -loadView () method.

Below is the openPdf method:

- (IBAction)openPdf:(id)sender{
// Creates an instance of a UIWebView
    UIWebView *aWebView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, 320,450)];

// Sets the scale of web content the first time it is displayed in a web view
    aWebView.scalesPageToFit = YES;
    [aWebView setDelegate:self];

//Create a URL object.
    NSURL *urlString = [NSURL URLWithString:[NSString stringWithFormat:@"http://portalarp.com.br/portal/%@",[[[[[[[delegateFunctions products] objectAtIndex:[delegateFunctions selectedProductIndex]] objectForKey:@"ata"] objectForKey:@"nm_arquivo"] objectForKey:@"text"] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] stringByReplacingOccurrencesOfString:@"\t" withString:@""]]];

//URL Requst Object
    NSURLRequest *requestObj = [NSURLRequest requestWithURL:urlString];

//load the URL into the web view.
    [aWebView loadRequest:requestObj];

    [self addSubview:aWebView];
    [aWebView release];
}