UIBarbuttonItem

在4.0里定义导航条按钮通常是生成普通按钮，再用它生成导航条专用按钮。

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1. UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];  
2. [button setBackgroundImage:[UIImage imageNamed:@"button_main.png"]  
3.                                       forState:UIControlStateNormal];  
4. [button addTarget:self action:@selector(GotoSettings)  
5.              forControlEvents:UIControlEventTouchUpInside];  
6. button.frame = CGRectMake(x, y, x1, x2);  
7.   
8. UIBarButtonItem *menuButton = [[UIBarButtonItem alloc] initWithCustomView:menu];  
9. self.navigationItem.rightBarButtonItem = menuButton;  
10.   
11. [button release];  
12. [menuButton release];  

如果是在导航条一边创建多个button，在4.0里是通过segmentcontrol来间接实现

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1. UISegmentedControl *SegmentedControl = [[UISegmentedControl alloc] initWithItems:  
2.                                          [NSArray arrayWithObjects:  
3.                                           @"开始",  
4.                                           @"暂停", nil]];  
5. [SegmentedControl addTarget:self action:@selector(segmentAction:)   
6.             forControlEvents:UIControlEventValueChanged];  
7. SegmentedControl.frame = CGRectMake(0, 0, 80, 30);  
8. SegmentedControl.segmentedControlStyle = UISegmentedControlStyleBar;  
9. SegmentedControl.momentary = YES;  
10. SegmentedControl.tintColor = [UIColor colorWithHue:0.6 saturation:0.33 brightness:0.69 alpha:0];  
11. //defaultTintColor = [segmentedControl.tintColor retain];    // keep track of this for later  
12. UIBarButtonItem *segmentBarItem = [[UIBarButtonItem alloc]   
13.                                        initWithCustomView:SegmentedControl];  
14. self.navigationItem.rightBarButtonItem = segmentBarItem;  

之后 通过Action方法判断是哪个button被按下

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1. - (void)segmentAction:(id)sender  
2. {  
3.       
4.     //NSLog(@"segmentAction: selected segment = %d", [sender selectedSegmentIndex]);  
5.     if ([sender selectedSegmentIndex] == 0) {  
6.         //[self startAll];  
7.           
8.     }else if ([sender selectedSegmentIndex] == 1) {  
9.         //[self stopAll];  
10.     }  
11.       
12. }  

在iOS 5.0中，导航条引入了新的方法 setLeftBarButtonItems:animated:和setRightBarButtonItems:animated:来直接定义左右侧的多个button，方便了许多

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1. UIBarButtonItem *startBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemPlay target:self action:@selector(startDownloadAll)];  
2. UIBarButtonItem *pauseBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemPause target:self action:@selector(stopDownloadAll)];  
3. [self.navigationItem setRightBarButtonItems:[NSArray arrayWithObjects: pauseBtn,startBtn,nil]]