导航VC的左右item代码

代码控制左右item：
　　 UIButton *btnCancel = [UIButton buttonWithType:UIButtonTypeCustom];
    btnCancel.frame=CGRectMake(0, 0, 60, 30);
    btnCancel.titleLabel.font=[UIFont systemFontOfSize:13];
    btnCancel.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;
    [btnCancel setTitle:@"返回" forState:UIControlStateNormal];
    [btnCancel addTarget:self action:@selector(buttonCancel:) forControlEvents:UIControlEventTouchUpInside];
    self.navigationItem.leftBarButtonItem=[[UIBarButtonItem alloc] initWithCustomView:btnCancel];
    
    UIButton *btnCommit = [UIButton buttonWithType:UIButtonTypeCustom];
    btnCommit.frame=CGRectMake(0, 0, 60, 30);
    btnCommit.titleLabel.font=[UIFont systemFontOfSize:13];
    btnCommit.contentHorizontalAlignment = UIControlContentHorizontalAlignmentRight;
    [btnCommit setTitle:@"提交" forState:UIControlStateNormal];
    [btnCancel addTarget:self action:@selector(commitAction:) forControlEvents:UIControlEventTouchUpInside];
    self.navigationItem.rightBarButtonItem=[[UIBarButtonItem alloc] initWithCustomView:btnCommit];


其他的方法：

		//第一种：这种设置出来的外观不好控制
    UIImage *searchimage=[UIImage imageNamed:@"search.png"];

    UIBarButtonItem *barbtn=[[UIBarButtonItem alloc] initWithImage:nil style:UIBarButtonItemStyleDone target:self action:@selector(searchprogram)];    
    barbtn.image=searchimage;
    self.navigationItem.rightBarButtonItem=barbtn;

		//第二种：这种图片将填满button，大小可控
    UIButton*rightButton = [[UIButton alloc]initWithFrame:CGRectMake(0,0,30,30)];
    [rightButton setImage:[UIImage imageNamed:@"back.png"]forState:UIControlStateNormal];
    [rightButton addTarget:self action:@selector(backto)forControlEvents:UIControlEventTouchUpInside];
    UIBarButtonItem*rightItem = [[UIBarButtonItem alloc]initWithCustomView:rightButton];
    self.navigationItem.leftBarButtonItem= rightItem;


 	 //第三种：

		UIBarButtonItem *anotherButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemBookmarks target:self action:@selector(methodtocall:) ]; 

	如何让navigationItem.rightBarButtonItem隐藏消失？
	self.navigationItem.rightBarButtonItem=nil；即可实现