1.选择器(UipickerView)UIPickerView是一个选择器，可以生成单列的选择器，也可生成多列的选择器，可以自定义选择器的外观。UIPickerView直接继承了UIView，没有继承UIControl，UIPickerView的事件由委托对象完成。
UIPickerVIew常用的属性和方法如下：
numberOfComponents只读，获取指定列包含的列表项的数量。
showSelectionIndicator控制是否显示UIPickerView中的选中标记(高亮背景)
-numberOfRowsInComponent:获取包含的列数量
-rorSizeForComponent:获取包含的指定列中列表项的大小。CGSize
-selectRow:inComponent:animated:设置选中指定列的特定列表项。
-selectRowInComponent:返回控件指定列中被选中的列表项
viewForRow:forComponent:返回指定列的列表项所使用的UiView控件UIPickerView包含的列及列包含的列表项由UIPickerViewDataSource对象设置，需要实现该对象的两个方法：
-numberOfComponentsInPickerView:该UIPickerView将通过该方法来判断包含多少列
-pickerView:numberOfRowsInComponent:通过该方法判断指定列包含多少列表项控制UIPickerView中的列的宽度、列表项的大小和外观，以及控件的事件响应，需要设置UIPickerViewDeletegate委托对象，根据需要，实现委托对象的如下方法：
-pickerView:rowHeightForComponent:该方法返回的CGFloat将作为该UIPickerView控件中指定列表项的高度
-pickerView:widthForComponent:返回的CGFloat作为指定列表项的宽度
- pickerView:titleForRow:forComponentNSString 作为指定列表项的文本标题
-pickerView:viewForRow:forComponent:reusingView:返回的UIView控件直接作为UIPickerView指定列的指定列表项
-pickerView:didSelectRow:inComponent:选中指定列的指定列表项是触发案例：单列选择器/多列选择器/级联选择器
定义三个UIPickerView分别用作单列、多列、级联选择器，并关联IBOutlet，控制器分别实现UIPickerViewDataSource,UIPickerViewDelegate
@PRoperty (weak, nonatomic) IBOutlet UIPickerView *picker;
@property (weak, nonatomic) IBOutlet UIPickerView *multiPicker;
@property (weak, nonatomic) IBOutlet UIPickerView *relPicker;
在控制器实现类中实现协议的方法：
NSArray* province;
NSArray* drink;
NSArray* size;
NSDictionary* city;
NSArray* prov;
NSString* selectedProv ;
-(void) viewDidLoad
{
[super viewDidLoad];
//初始化NSArray对象
province = [NSArray arrayWithObjects:@"广东",@"湖北",@"北京",@"四川",@"浙江",nil];
size = [NSArray arrayWithObjects:@"大杯",@"中杯",@"小杯", nil];
drink = [NSArray arrayWithObjects:@"红茶",@"绿茶",@"咖啡",@"拿铁",@"芒果冰沙", nil];
city = [NSDictionary dictionaryWithObjectsAndKeys:
[NSArray arrayWithObjects:@"朝阳区",@"海淀区",@"大兴区",@"房山区", nil],@"北京",
[NSArray arrayWithObjects:@"广州",@"深圳",@"珠海", nil],@"广东",
[NSArray arrayWithObjects:@"武汉",@"荆州",@"宜昌",@"荆门",@"黄冈", nil],@"湖北",nil];
prov = [[city allKeys] sortedArrayUsingSelector:@selector(compare:)];
//为UIPickerView设置dataSrouce和delegate
self.picker.dataSource = self;
self.picker.delegate = self;
self.multiPicker.dataSource = self;
self.multiPicker.delegate = self;
selectedProv = [prov objectAtIndex:0];
self.relPicker.dataSource = self;
self.relPicker.delegate = self;
}
//UIPickerViewDataSource中定义的方法，该方法返回值决定控件包含多少列
-(NSInteger) numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
if(pickerView == self.multiPicker)
{
return 2;
}
else if(pickerView == self.relPicker)
{
return 2;
}
return 1;//返回1 表明只包含1列
}
//UIPickerViewDataSrouce定义，该方法返回值决定控件指定列包含多少列表项
-(NSInteger) pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
if(pickerView == self.multiPicker)
{
if(component == 0)//如果是第一列
{
return size.count;
}
return drink.count; //其它列
}
else if(pickerView == self.relPicker)
{
if(component == 0)
{
return prov.count;
}
NSInteger c = [[city objectForKey:selectedProv] count];
return c;
}
return province.count;
}
//UiPickerViewDelegate定义方法返回值作为指定列的标题文本
-(NSString*) pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
if(pickerView == self.multiPicker)
{
if(component == 0)
{
return [size objectAtIndex:row];
}
return [drink objectAtIndex:row];
}
else if(pickerView == self.relPicker)
{
if(component ==0)
{
return [prov objectAtIndex:row];
}
return [[city objectForKey:selectedProv] objectAtIndex:row];
}
return [province objectAtIndex:row];
}
//选中指定列和列表项时触发
-(void) pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
NSString* msg ;
if(pickerView == self.picker)
{
msg =[NSString stringWithFormat:@"选中的省份是%@",[province objectAtIndex:row]];
}
else if(pickerView == self.multiPicker)
{
NSArray* tmp = component == 0? size : drink;
msg =[NSString stringWithFormat:@"选中的是%@",[tmp objectAtIndex:row]];
}
else if(pickerView == self.relPicker)
{
if(component ==0)
{
selectedProv = [prov objectAtIndex:row];
//控制重写加载第二个列表
[self.relPicker reloadComponent:1];
}
NSArray* tmp = component ==0?prov:[city objectForKey:selectedProv];
msg = [NSString stringWithFormat:@"选中的是%@",[tmp objectAtIndex:row]];
}
UIAlertView* alert = [[UIAlertView alloc]
initWithTitle:@"提示"
message:msg
delegate:nil cancelButtonTitle:@"确定" otherButtonTitles: nil];
[alert show];
}
-(CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component
{
if(pickerView == self.multiPicker || pickerView == self.relPicker)
{
if(component==0)
{
return 90;
}
return 210;
}
return 390;
}