在iPhone的iPhone OS 4.0的导航栏中，后退按钮不可见

Question

在我的应用程序（基于视图）中，后退按钮在导航栏中不可见。 如果我单击该按钮，则这些操作将正常运行。 对我来说很奇怪。 后退按钮是可见的，并且在iPhone OS 3.0和其他操作系统（OS 4.0除外）中可以正常使用。 我目前在iPhone OS 4.0中工作。

这是我的代码：

UIButton *btn=[[UIButton alloc] init];

[btn setImage:[UIImage imageNamed:@"Back.png"] forState:UIControlStateNormal];

[btn addTarget:self action:@selector(backAction) forControlEvents:UIControlEventTouchUpInside];
[btn setImageEdgeInsets:UIEdgeInsetsMake(0, 70, 0, 20)];
UIBarButtonItem *b=[[UIBarButtonItem alloc] initWithCustomView:btn];    
self.navigationItem.leftBarButtonItem=b;
[b release];
[btn release]; 

注意：它仅在iPhone OS 4.0上不起作用。 那么我该如何实现呢？

Answer 1

您只需在任何地方替换此代码，即可在OS 4.0中正常工作。

UIButton *btn=[[UIButton alloc] initWithFrame:CGRectMake(0, 0, 70, 40)];

UIView *myView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 70, 40)];

[myView addSubview:btn];

UIImageView *myImage = [[UIImageView alloc] initWithFrame:CGRectMake(0,5,50,30)];

[myImage setImage:[UIImage imageNamed:@"Back.png"]];

[myView addSubview:myImage];

[btn addTarget:self action:@selector(lOut) forControlEvents:UIControlEventTouchUpInside];

UIBarButtonItem *b1 = [[UIBarButtonItem alloc] initWithCustomView:myView];

self.navigationItem.leftBarButtonItem = b1;

[btn release];

[b1 release];

[myView release];

[myImage release];

希望对您有所帮助。

Answer 2

UIButton *btn=[[UIButton alloc] initWithFrame:CGRectMake(0, 0, 44, 40)];
[btn setImage:[UIImage imageNamed:@"info44.png"] forState:UIControlStateNormal];
[btn setImage:[UIImage imageNamed:@"info44_glowing.png"] forState:UIControlStateHighlighted];   
[btn addTarget:[AppDelegate sharedAppDelegate]  action:@selector(settingAction:) forControlEvents:UIControlEventTouchUpInside];
UIBarButtonItem *settingButton = [[UIBarButtonItem alloc] initWithCustomView:btn];
self.navigationItem.leftBarButtonItem = settingButton;
[btn release];
[settingButton release];