如何获取backBarButtonItem宽度？

Question

我尝试获取backBarButtonItem宽度：

UIBarButtonItem *leftBtn = self.navigationItem.backBarButtonItem;
UIView *view = [leftBtn valueForKey:@"view"];
CGFloat width;
if(view){
    width=view.frame.size.width;
}
NSLog(@"width %f", width);

但在控制台中：width 0.000000

你知道我做错了什么吗？有了self.navigationItem.rightBarButtonItem，这就是工作。

Answer 1

UIButton *addButton = [UIButton buttonWithType:UIButtonTypeCustom];
    CALayer *btnLayer = [addButton layer];
        [btnLayer setMasksToBounds:YES];
        [btnLayer setCornerRadius:1.0f];
    [addButton setFrame:CGRectMake(0, 0, 45, 30)];
    [addButton setBackgroundColor:[UIColor orangeColor]];
    [addButton setTitle:@"Title" forState:UIControlStateNormal];
    addButton.titleLabel.font = [UIFont systemFontOfSize:14.0];
    [addButton addTarget:self action:@selector(Onclickevent:) forControlEvents:UIControlEventTouchUpInside];
    UIBarButtonItem *barButtonItem = [[UIBarButtonItem alloc] initWithCustomView:addButton];
    [self.navigationItem setRightBarButtonItem:barButtonItem];