iOS 为键盘添加隐藏按钮

// 为键盘添加隐藏按钮
    UIToolbar * backView = [[UIToolbar alloc]initWithFrame:CGRectMake(, , , )];
    [backView setBarStyle:UIBarStyleDefault];

    UIBarButtonItem * btnSpace = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:self action:nil];

    UIButton *btn = [UIButton buttonWithType:UIButtonTypeSystem];
    [btn setTitle:@"隐藏键盘" forState:UIControlStateNormal];
    btn.frame = CGRectMake(, , , );
    [btn addTarget:self action:@selector(cancelInput:) forControlEvents:UIControlEventTouchUpInside];
    UIBarButtonItem *doneBtn = [[UIBarButtonItem alloc]initWithCustomView:btn];
    NSArray * buttonsArray = @[btnSpace,doneBtn];
    [backView setItems:buttonsArray];
    [self.searchBar setInputAccessoryView:backView];