自定义导航栏按钮UIBarButtonItem 文字或图片

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。

 UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
 [button setBackgroundImage:[UIImage imageNamed:@"button_main.png"]
                                       forState:UIControlStateNormal];
 [button addTarget:self action:@selector(GotoSettings)
              forControlEvents:UIControlEventTouchUpInside];
 button.frame = CGRectMake(x, y, x1, x2);

 UIBarButtonItem *menuButton = [[UIBarButtonItem alloc] initWithCustomView:menu];
 self.navigationItem.rightBarButtonItem = menuButton;

 [button release];
 [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

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

之后 通过Action方法判断是哪个button被按下

 - (void)segmentAction:(id)sender
 {

     //NSLog(@"segmentAction: selected segment = %d", [sender selectedSegmentIndex]);
     if ([sender selectedSegmentIndex] == 0) {
         //[self startAll];

     }else if ([sender selectedSegmentIndex] == 1) {
         //[self stopAll];
     }

 }

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

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