1.UIPickView什么时候用?

• 通常在注册模块，当用户需要选择一些东西的时候，比如说城市，往往
弹出一个PickerView给他们选择。
• 老虎机效果

UIPickView和TableView一样,想要展示数据也要设置数据源和代理

设置数据源

self.pickView.dataSource = self; 设置代理
self.pickView.delegate = self;

• 遵守数据源,代理协议:

@interface ViewController () <UIPickerViewDataSource,UIPickerViewDelegate>
@property (weak, nonatomic) IBOutlet UIPickerView *pickView; @end
//实现数据源代理⽅方法:
//总共有多少列
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView
*)pickerView
{
return 3; 
}
第component列有多少行.
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
return 4; 
}
返回每一列的宽度
- (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent: (NSInteger)component
{
}
返回第⼀列⾼高度
- (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component
{
return 50;
 }
返回每一行的标题
- (nullable NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
return @"gaowei"; 
}
返回每⼀一⾏行的视图UIView
- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow: (NSInteger)row forComponent:(NSInteger)component reusingView: (nullable UIView *)view
{
    UIButton *btn = [UIButton
buttonWithType:UIButtonTypeContactAdd];
return btn; 
}