Navigationbar的相关设置

1.navigationbar上的左右按钮的位置的改变

如果想要图示1的效果代码如下：

 UIButton *settingBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    [settingBtn setImage:[UIImage imageNamed:@"铃铛"] forState:UIControlStateNormal];
    settingBtn.frame = CGRectMake(0, 0, 60, 40);
    [settingBtn addTarget:self action:@selector(rightBtnClick:) forControlEvents:UIControlEventTouchUpInside];
    UIBarButtonItem *rightBar = [[UIBarButtonItem alloc]initWithCustomView:settingBtn];
    UIBarButtonItem *negativeSpacer = [[UIBarButtonItem alloc]
                                       initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace
                                       target:nil action:nil];
    negativeSpacer.width = -20;
    self.navigationItem.leftBarButtonItems = [NSArray arrayWithObjects:negativeSpacer,rightBar,nil];

如果想要图示2的效果代码如下

 UIBarButtonItem *left = [[UIBarButtonItem alloc]initWithImage:[UIImage imageNamed:@"三横线"] style:UIBarButtonItemStylePlain target:self action:@selector(leftBtnClick:)];
    self.navigationItem.leftBarButtonItem = left;

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