绘制自定义 UIBarButtonItem 的正确方法是什么？

Question

我正在编写自定义 UINavigationBar。由于该应用程序应该在 iOS 4 上运行，因此无法使用 new customization options available on iOS 5。

也就是说，我对 UINavigationBar 进行了子类化，以避免使用效果很好的类别，如下图所示。

UIBarButtonItems 不能正常工作。

我尝试继承 UIBarButtonItem 类并覆盖 drawRect 方法，但没有任何改变。

CustomUIBarButtonItem *backButton = [[CustomUIBarButtonItem alloc] initWithTitle:@"Notícias" style:UIBarButtonItemStylePlain target:nil action:nil];
self.navigationItem.backBarButtonItem = backButton;
[backButton release];

然后我也尝试设置下面的图像，但也没有用。

UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"noticias_back.png"] style:UIBarButtonItemStyleBordered target:nil action:nil];
self.navigationItem.backBarButtonItem = backButton;
[backButton release];

那么，我该怎么做呢？

Answer 1

我只是做一些类似...

UIButton *searchButton = [UIButton buttonWithType:UIButtonTypeCustom];
[searchButton setBackgroundImage:[UIImage imageNamed:@"search"] forState:UIControlStateNormal];
[searchButton setBackgroundImage:[UIImage imageNamed:@"search_pressed"] forState:UIControlStateHighlighted];
[searchButton addTarget:self action:@selector(selectedSearch) forControlEvents:UIControlEventTouchUpInside];
[searchButton setImage:[UIImage imageNamed:@"search"] forState:UIControlStateNormal];
[searchButton sizeToFit];

self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:searchButton];

Answer 2

您必须在按下或模态显示之前设置自定义按钮。例如：

ENPurchaseEditView *purchaseView = [[ENPurchaseEditView alloc] initWithNibName:@"ENPurchaseEditView" bundle:nil];

// customized left button to cancel - not back.
ENBarButtonImageItem *cancelBtn = 
[[ENBarButtonImageItem alloc] initWithFrame:CGRectMake(0, 0, 29, 29)
                                      image:[UIImage imageNamed:@"btn_cancel.png"]
                            backgroundImage:nil 
                                     target:purchaseView 
                                     action:@selector(cancel:)];   

// setLeftBarButtonItem before you push or present.
// in this view, I also setHidesBackButton = YES in the init so my custom left
// shows up.
[[purchaseView navigationItem] setLeftBarButtonItem:cancelBtn];
[cancelBtn release];    

// Edit purchase in full modal view.
// This could be a push - in my case I'm presenting a navController.
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:purchaseView];
[[self navigationController] presentModalViewController:navController animated:YES];

在我的例子中，ENBarButtonImageItem 是一个自定义 UIBarButtonItem。这是我的课：

#import "ENBarButtonImageItem.h"

@implementation ENBarButtonImageItem

- (id)initWithFrame:(CGRect)frame 
              image:(UIImage*)image 
    backgroundImage:(UIImage*)bgImage
{
    _button = [UIButton buttonWithType:UIButtonTypeCustom];
    [_button setFrame:frame];

    self = [super initWithCustomView:_button];
    if (self) 
    {
        if (image)
            [_button setImage:image forState:UIControlStateNormal];

        if (bgImage)
            [_button setBackgroundImage:bgImage forState:UIControlStateNormal];

    }
    return self;    
}

- (id)initWithFrame:(CGRect)frame 
              image:(UIImage*)image 
    backgroundImage:(UIImage*)bgImage 
             target:(id)target 
             action:(SEL)selector
{
    self = [self initWithFrame:frame image:image backgroundImage:bgImage];
    if (self)
    {
        [_button addTarget:target action:selector forControlEvents:UIControlEventTouchUpInside];
    }

    return self;
}

- (void)dealloc
{
    [super dealloc];
    [_button release];
}

- (void)addTarget:(id)target action:(SEL)selector forControlEvents:(UIControlEvents)controlEvents
{
    [_button addTarget:target action:selector forControlEvents:controlEvents];
}

- (void)setImage:(UIImage *)image forState:(UIControlState)state
{
    [_button setImage:image forState:state];
}

- (void)setBackgroundImage:(UIImage *)image forState:(UIControlState)state
{
    [_button setImage:image forState:state];
}

@end