UIPickerView簡單使用

 先說一下當個組件選取器，我們創建一個數組NSAray來保存選取器中的內容；選取器本身不會儲存任何數據，，它通過調用數據源和委託方法來顯示數據；但是對於大量數據的數據源，數組並不合適，我們可以做一個靜態列表如plist文件或者URL載入，和後面將講在文件中獲取數據，還以多個選取器的之間的關聯如何實現；先說下簡單的單個選取器:

先把效果圖貼出來

1.新建工程名爲PickerViewDemo ， File->New->Project ->single View Application -> next

2.在視圖上添加選取器

pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, 320, 216)];
//    指定Delegate
    pickerView.delegate=self;
//    顯示選中框
    pickerView.showsSelectionIndicator=YES;
    [self.view addSubview:pickerView];

以上可以在視圖顯示一個選取器，但是內容空白，pickerView.showsSelectionIndicator=YES;是這隻當前選取器所選中的內容：

選取器上顯示數據，必須依賴兩個協議，UIPickerViewDelegate和UIPickerViewDataSource，把他們添加到ViewController.h文件中

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<UIPickerViewDelegate,UIPickerViewDataSource>
{

    UIPickerView *pickerView;
    NSArray *pickerData;

}

@end

3.然後在.m文件的ViewDidLoad中初始化界面

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, 320, 216)];
//    指定Delegate
    pickerView.delegate=self;
//    顯示選中框
    pickerView.showsSelectionIndicator=YES;
    [self.view addSubview:pickerView];

    NSArray *dataArray = [[NSArray alloc]initWithObjects:@"許嵩",@"周杰倫",@"梁靜茹",@"許飛",@"鳳凰傳奇",@"阿杜",@"方大同",@"林俊杰",@"胡夏",@"邱永傳", nil];

    pickerData=dataArray;

//     添加按鈕
    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];

}

4.實現UIPickerView的代理方法，將數據顯示在選取器上所需要幾個方法

#pragma mark -
#pragma mark Picker Date Source Methods

//返回顯示的列數
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    return 1;
}
//返回當前列顯示的行數
-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return [pickerData count];
}

#pragma mark Picker Delegate Methods

//返回當前行的內容,此處是將數組中數值添加到滾動的那個顯示欄上
-(NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    return [pickerData objectAtIndex:row];
}

前兩個是數據源的代理方法，一個是返回列，有幾個選取器就返回幾，第二個是設置選取器有多少行，因爲就這一個選取器，所以直接返回行數，即數組元素個數多少；第三個代理方法是將數組元素添加到了選取器上面顯示；

說一下兩個協議實例方法,參考http://www.cnblogs.com/edsioon/

UIPickerViewDelegate中的實例方法

-(void) pickerView: (UIPickerView *)pickerView didSelectRow: (NSInteger)row inComponent: (NSInteger)component

作用: 當用戶選擇某個row時,picker view調用此函數

參數: pickerView representing the picker view request the data

-(CGFloat) pickerView:(UIPickerView *)pickerView rowHeightForComponent: (NSInteger) component

作用:由picker view調用,當其在繪製row內容,需要row的高度時

-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger) component

作用: 當picker view需要給指定的component.row指定title時,調用此函數

-(UIView *)pickerView: (UIPickerView *)pickerView view ForRow:(NSInteger) row forComponent:(NSInteger) component reusingView:(UIView *) view

作用: 當picker view需要給指定的component.row指定view時,調用此函數.返回值爲用作row內容的view

參數: view參數, a view object that was previously used for this rows, but is now hidden and cached by the picker view

- （CGFloat)pickerView: (UIPickerView *)pickerView widthForComponent:(NSInteger) component

作用:當picker view 需要row的寬度時,調用此函數

UIPickerViewDataSource中的實例方法

按照官方文檔的說法,UIPickerViewDataSource這個協議僅有的功能就是提供picker view中component的個數和各個component中的row的個數,雖然名爲datasource,但是它工作於MVC的C中

本協議僅有兩個實例方法,均需要實現

-(NSInteger) numberOfComponentsInPickerView:(UIPickerView *)pickerView

作用:返回pickerView應該有幾個component

-(NSInteger) pickerView:(UIPickerView *) pickerView numberOfRowsInComponent:(NSInteger) component

作用:返回指定component應該有幾個row

5.關於按鈕響應事件，關於按鈕的形成和添加響應事件不再提，前面都有，

-(void) buttonPressed:(id)sender
{
     NSInteger row =[pickerView selectedRowInComponent:0];
     NSString *selected = [pickerData objectAtIndex:row];
     NSString *message = [[NSString alloc] initWithFormat:@"你選擇的是:%@",selected];

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示"
                                                    message:message
                                                   delegate:self
                                          cancelButtonTitle:@"OK"
                                          otherButtonTitles: nil];
    [alert show];

}

[pickerViewselectedRowInComponent:0];方法返回當前被選中的索引序號，這是UIPickerView的實例方法，在官方文檔中

UIPickerView還有其他實例方法

- (NSInteger) numberOfRowsInComponent:(NSInteger)component

參數爲component的序號(從左到右,以0起始),返回指定的component中row的個數

-(void) reloadAllComponents

調用此方法使得PickerView向delegate: Query for new data for all components

-(void) reloadComponent: (NSInteger) component

參數爲需更新的component的序號,調用此方法使得PickerView向其delegate: Query for new data

-(CGSize) rowSizeForComponent: (NSInteger) component

參數爲component的序號,返回值爲the size of rows in the given components, picker view 通過調用委託方法中的pickerView:widthForComponent:和pickerView:rowHeightForComponent:獲得返回值

-(NSInteger) selectedRowInComponent: (NSInteger) component

參數爲component的序號,返回被選中row的序號,若無row被選中,則返回-1

-(void) selectRow: (NSInteger)row inComponent: (NSInteger)component animated: (BOOL)animated

作用:在代碼指定要選擇的某component的某row

參數:row序號,component序號,BOOL值(若爲YES,轉動spin到你選擇的新值,若爲NO,直接顯示你選擇的值)

-(UIView *) viewForRow: (NSInteger)row forComponent: (NSInteger)component

參數:row序號,component序號,返回由委託方法pickerView:viewForRow:forComponentreusingView:指定的view.如果委託對象並沒有實現這個方法,或者說這個view並不是可見的,則返回nil

附上源代碼: http://download.csdn.net/detail/duxinfeng2010/4410909