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//创建自定义视图
UIView *vs = [[UIView alloc] initWithFrame:CGRectMake(2, 2, 60, 40)];
//设置自定义视图的背景颜色
vs.backgroundColor = [UIColor redColor];
//加载自定义视图
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:vs];