UIPickerView委託方法titleForRow執行不正確？

我在爲UIPickerview實現委託方法時面臨一個問題。問題的描述是，我想在pickerview中有3個組件，每個組件具有不同的行數。造成這種情況的代碼如下UIPickerView委託方法titleForRow執行不正確？

-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView 
{ 
    return 3; 

} 

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

{ 
    NSInteger rows; 
    if (0 == component) 
     rows = 5; 
    else if (1 == component) 
     rows = 10; 
    else 
     rows = 15; 

    NSLog(@"Number of rows returned for component %d are rows %d",component, rows); 
    return rows; 
}

在此之後我在執行「titleForRow」委託方法代碼是如下：

#pragma -mark UIPIckerView Delegate Methods 
-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component 
{ 
     //NSString *temp; 


     //temp = [[NSString alloc] initWithString:[self.pocModelData.arrayOfDistricts objectAtIndex:row]]; 
    if (0 == component) 
    { 
    NSLog(@"String returned is %@ for row %d for component %d", [self.pocModelData.arrayOfDistricts objectAtIndex:row], row, component); 
    return [self.pocModelData.arrayOfDistricts objectAtIndex:row]; 
    } 
    else if 
     (1 == component){ 
     NSLog(@"String returned is %@ for row %d for component %d", [self.pocModelData.arrayOfDistricts objectAtIndex:row], row, component); 
    return [self.pocModelData.arrayOfDistricts objectAtIndex:row]; 
    }else{ 
     NSLog(@"String returned is %@ for row %d for component %d", [self.pocModelData.arrayOfDistricts objectAtIndex:row], row, component); 
    return [self.pocModelData.arrayOfDistricts objectAtIndex:row]; 
    } 
     //return temp; 
     // return [self.pocModelData.arrayOfDistricts objectAtIndex:row]; 
}

上執行此方法爲每個組件只返回3行，如以下語句所示

2013-05-18 02:00:40.743 PopOverControllerExample[8228:c07] Number of rows returned for component 0 are rows 5 
2013-05-18 02:00:41.221 PopOverControllerExample[8228:c07] Number of rows returned for component 1 are rows 10 
2013-05-18 02:00:41.696 PopOverControllerExample[8228:c07] Number of rows returned for component 2 are rows 15 
2013-05-18 02:00:42.035 PopOverControllerExample[8228:c07] Number of rows returned for component 0 are rows 5 
2013-05-18 02:00:43.761 PopOverControllerExample[8228:c07] String returned is 1 for row 0 for component 0 
2013-05-18 02:00:44.687 PopOverControllerExample[8228:c07] String returned is 2 for row 1 for component 0 
2013-05-18 02:00:45.048 PopOverControllerExample[8228:c07] String returned is 3 for row 2 for component 0 
2013-05-18 02:00:45.544 PopOverControllerExample[8228:c07] Number of rows returned for component 1 are rows 10 
2013-05-18 02:00:46.131 PopOverControllerExample[8228:c07] String returned is 1 for row 0 for component 1 
2013-05-18 02:00:46.620 PopOverControllerExample[8228:c07] String returned is 2 for row 1 for component 1 
2013-05-18 02:00:47.380 PopOverControllerExample[8228:c07] String returned is 3 for row 2 for component 1 
2013-05-18 02:00:47.772 PopOverControllerExample[8228:c07] Number of rows returned for component 2 are rows 15 
2013-05-18 02:00:48.543 PopOverControllerExample[8228:c07] String returned is 1 for row 0 for component 2 
2013-05-18 02:00:48.915 PopOverControllerExample[8228:c07] String returned is 2 for row 1 for component 2 
2013-05-18 02:00:49.461 PopOverControllerExample[8228:c07] String returned is 3 for row 2 for component 2

我不能理解爲什麼每個組件只執行3次？我使用一組數據填充行，所以數據源對於所有這些數據源都是通用的。這裏有什麼問題，我現在無法把握和困擾一段時間？任何指導是高度讚賞和提前感謝。

來源

2013-05-17 Mobility Associate Architect

它只查詢可見的值。在微調中心的第0行，你有3行可見。一旦你旋轉它將查詢其他值。

來源

2013-05-17 20:40:38 mvds

thnks @mvds，但你能詳細闡述一下嗎？糾正我，如果我錯了，但你的意思是，它的返回3值只會導致，只有3行可見？ –

@experimentalist是的，當需要顯示更多的值時，它們被請求。只需旋轉選取器，您就會看到需要其他值。 – mvds

非常感謝解釋..它幫助我解決了我的問題!! :) –

UIPickerView委託方法titleForRow執行不正確？

回答

相關問題