ios - 为什么我的 UIButton 没有显示在我的 subview 中？ iPad应用程式

Question

有人可以帮助我理解为什么我的 UIButton 没有显示在我的自定义 UIView 中吗？ 在下面的代码中，我发布了 initWithFrame 方法:

- (id)initWithFrame:(CGRect)frame{

     self = [super initWithFrame:frame];

    if (self) {
    self.backgroundColor =[UIColor whiteColor];

    UIToolbar *toolbar = [[UIToolbar alloc]initWithFrame:CGRectMake(0, 0,frame.size.width, 50)];
    toolbar.backgroundColor = [UIColor grayColor];

    UIBarButtonItem *cancelBarButton = [[UIBarButtonItem alloc]initWithTitle:@"Cancel" style:UIBarButtonItemStylePlain target:self action:@selector(dismissNewInvoiceView:)];
    UIBarButtonItem *flexibleSpace = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];
    UIBarButtonItem *saveBarButton = [[UIBarButtonItem alloc] initWithTitle:@"Save" style:UIBarButtonItemStylePlain target:self action:@selector(saveNewInvoice:)];
    [saveBarButton setEnabled:NO];
    NSArray *arrayOfItems = [[NSArray alloc]initWithObjects:cancelBarButton,flexibleSpace, saveBarButton, nil];
    [toolbar setItems:arrayOfItems];

    UILabel *headerViewLabel = [[UILabel alloc]initWithFrame:CGRectMake(335, 15, 200, 20)];
    headerViewLabel.text = @"New Invoice";
    [toolbar addSubview:headerViewLabel];

    [self addSubview:toolbar];

    UIButton *selectCustomerButton = [[UIButton alloc]initWithFrame:CGRectMake(25, 200, 60, 60)];
    selectCustomerButton.imageView.image = [UIImage imageNamed:@"Farmer.png"];

    [self addSubview:selectCustomerButton];
    [self bringSubviewToFront:selectCustomerButton];

    UILabel *invoiceNumberLabel = [[UILabel alloc]initWithFrame:CGRectMake(25, 55, 150, 25)];
    [invoiceNumberLabel setFont:[UIFont fontWithName:@"Verdana" size:14]];
    invoiceNumberLabel.text = @"Invoice number:";
    [self addSubview:invoiceNumberLabel];

    UITextField *invoiceNumberField = [[UITextField alloc]initWithFrame:CGRectMake(140, 53, 150, 30)];
    [invoiceNumberField setFont:[UIFont fontWithName:@"Verdana" size:25]];
    invoiceNumberField.placeholder = @"25/13";
    [self addSubview:invoiceNumberField];

    UILabel *dateOfCreationLabel = [[UILabel alloc]initWithFrame:CGRectMake(500, 55, 150, 25)];
    [dateOfCreationLabel setFont:[UIFont fontWithName:@"Verdana" size:14]];
    dateOfCreationLabel.text = @"Date of creation:";
    [self addSubview:dateOfCreationLabel];







}
return self;}

为什么 UILabels 通过实现 addSubview 方法可以正确显示，而 UIButtons 却不能？

问候

Answer 1

不要这样做:

selectCustomerButton.imageView.image = [UIImage imageNamed:@"Farmer.png"]

使用

[selectCustomerButton setImage:[UIImage imageNamed:@"Farmer.png"] forState:UIControlStateNormal];

该按钮根据其状态设置自己的 ImageView 图像，您不能自己访问和设置 ImageView 的图像。