Can not load UIImage on button

I want to add UIImage on button?but the del.png can't show on my button?
What can i do?

I try many load Image Method?but no effect?such as:

UIImage* delImage = [[UIImage alloc] initWithContentsOfFile:@"del.png"];
 
 UIImage* delImage = [UIImage imageNamed:@"del.png"];
 
 UIImage* delImage =[UIImage imageWithContentsOfFile:@"del.png"];
 
 CalDelBtn *BookItem = [[CalDelBtn alloc] initWithFrame:CGRectMake(startPointX, startPointY, 75, 113) statuePicture:delImage];
 

Please give me some advice?thank you!!

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