iOS 返回按钮

• 方法一：

UIButton *backBtn =[UIButton buttonWithType:(UIButtonTypeCustom)];
backBtn.frame = CGRectMake(0, 0, 20, 20);
[backBtn setImage:[UIImage imageNamed:@"fanhuijiantou"] forState:UIControlStateNormal];
backBtn.imageEdgeInsets = UIEdgeInsetsMake(0, -7, 0, 7);
[backBtn addTarget:self action:@selector(onLibraryButtonClicked) forControlEvents:(UIControlEventTouchUpInside)];
UIBarButtonItem *leftItem = [[UIBarButtonItem alloc]initWithCustomView:backBtn];
//self.navigationItem.leftBarButtonItem.width = 100*SCALE;
   
UIBarButtonItem *placeItem = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
self.navigationItem.leftBarButtonItems = @[leftItem,placeItem];