1.UIPickerView的宽度和高度是固定的,纵向是320216,横向是568162
2.属性:
@property(nonatomic,assign)idUIPickerViewDataSource> dataSource; (类似于UITableView)
@property(nonatomic,assign)idUIPickerViewDelegate>delegate; (类似于UITableView)
(BOOL)showsSelectionIndicator// 是否显示选择指示器 ,即是一个蓝色的条
pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, 320, 216)];
// 指定Delegate
pickerView.delegate=self;
// 显示选中框
pickerView.showsSelectionIndicator=YES;
[self.view addSubview:pickerView];
选取器上显示数据，必须依赖两个协议，UIPickerViewDelegate和UIPickerViewDataSource，把他们添加到ViewController.h文件中
@interface ViewController : UIViewController<UIPickerViewDelegate,UIPickerViewDataSource>
{
UIPickerView *pickerView;
NSArray *pickerData;
}
@end
pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, 320, 216)];
// 指定Delegate
pickerView.delegate=self;
// 显示选中框
pickerView.showsSelectionIndicator=YES;
[self.view addSubview:pickerView];
NSArray *dataArray = [[NSArray alloc]initWithObjects:@"许嵩",@"周杰伦",@"梁静茹",@"许飞",@"凤凰传奇",@"阿杜",@"方大同",@"林俊杰",@"胡夏",@"邱永传", nil];
pickerData=dataArray;
// 添加按钮
CGRect frame = CGRectMake(120, 250, 80, 40);
UIButton *selectButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
selectButton.frame=frame;
[selectButton setTitle:@"SELECT" forState:UIControlStateNormal];
[selectButton addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:selectButton];
}
//返回显示的列数
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
return 1;
}
//返回当前列显示的行数
-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
return [pickerData count];
}
#pragma mark Picker Delegate Methods
//返回当前行的内容,此处是将数组中数值添加到滚动的那个显示栏上
-(NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
return [pickerData objectAtIndex:row];
}
说一下两个协议实例方法
UIPickerViewDelegate中的实例方法
- (void) pickerView: (UIPickerView *)pickerView didSelectRow: (NSInteger)row inComponent: (NSInteger)component
// 当其在绘制row内容,需要row的高度时
(CGFloat) pickerView:(UIPickerView *)pickerView rowHeightForComponent: (NSInteger) component
// 返回指定component.row显示的文本
(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger) component
// 当picker view需要给指定的component.row指定view时,调用此函数.返回值为用作row内容的view
(UIView *)pickerView: (UIPickerView *)pickerView view ForRow:(NSInteger) row forComponent:(NSInteger) component reusingView:(UIView *) view
// row的宽度
(CGFloat)pickerView: (UIPickerView *)pickerView widthForComponent:(NSInteger) component
按照官方文档的说法,UIPickerViewDataSource这个协议仅有的功能就是提供picker view中component的个数和各个component中的row的个数,虽然名为datasource,但是它工作于MVC的C中
本协议仅有两个实例方法,均需要实现:
(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
// 返回每一列对应的行数
(NSInteger) pickerView:(UIPickerView *) pickerView numberOfRowsInComponent:(NSInteger) component
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示"
message:message
delegate:self
cancelButtonTitle:@"OK"
otherButtonTitles: nil];
[alert show];
}
- (NSInteger) numberOfRowsInComponent:(NSInteger)component
// 刷新所有的列
(void) reloadAllComponents
// 刷新指定的列
(void) reloadComponent: (NSInteger) component
(CGSize) rowSizeForComponent: (NSInteger) component
// 获取某列选择的行数
(NSInteger) selectedRowInComponent: (NSInteger) component
// 选择一行
(void) selectRow: (NSInteger)row inComponent: (NSInteger)component animated: (BOOL)animated
(UIView *) viewForRow: (NSInteger)row forComponent: (NSInteger)component
PS：多个component对应不同title的方法
有时候我们需要有多个component的UIPickerView并且对应不同的内容，比如地区的选择，需要有省份和城市两个选项，选择不同的省份，城市要相应发生变化。
下面假设component数量为2。
使用指定title的函数，根据[pickerView selectedRowInComponent:0]的不同来指定第二个component的title
我们还要指定刷新事件。
