一个 ViewController 中的三个 UIPickerViews

Question

我有三个 UIPickerView，我在一个 ViewController 中使用它们。它需要彼此独立，因为我需要保存每个结果，但是当我运行它时，它会看到三个pickerView，当你选择不同的 UIPickerView 时，它们也保存了相同的结果。 ViewController.m 文件：

 @interface ViewController (){
 NSArray *_pickerData;
 NSArray *_pickerData2;
 NSArray *_pickerData3;

__weak IBOutlet UITextField *max;
__weak IBOutlet UITextField *m2;
__weak IBOutlet UITextField *m3;
 }
@end

@implementation ViewController


   - (void)viewDidLoad {
     [super viewDidLoad];
 _pickerData = @[@"Apple",@"Avocado",@"Asparagus",@"Grapefruit"];
    _pickerData2 = @[@"Apple",@"Avocado",@"Asparagus",@"Grapefruit"];
    _pickerData3 = @[@"Apple",@"Avocado",@"Asparagus",@"Grapefruit"];
// Do any additional setup after loading the view, typically from a nib.
self.picker.dataSource = self;
self.picker.delegate = self;
self.picker2.dataSource = self;
self.picker2.delegate = self;
self.picker3.dataSource = self;
self.picker3.delegate = self;
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
// The number of columns of data
- (int)numberOfComponentsInPickerView:(UIPickerView *)pickerView
 {
return 1;
 }

 // The number of rows of data
 - (int)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
 {
return _pickerData.count;
  }
  - (int)picker2View:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
  {
return _pickerData2.count;
  }
  - (int)picker3View:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
  {
return _pickerData3.count;
  }
 - (NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:           (NSInteger)component                    
   {
   self->max.text = [NSString stringWithFormat:@"%@", _pickerData[row]];

    return _pickerData[row];

    }
   - (NSString*)pickerView2:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent: (NSInteger)component
     {
     self->m2.text = [NSString stringWithFormat:@"%@", _pickerData2[row]];
     return _pickerData2[row];
      }
  - (NSString*)pickerView3:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:   (NSInteger)component
      {
       self->m3.text = [NSString stringWithFormat:@"%@", _pickerData2[row]];
       return _pickerData3[row];
       }
       @end

当我运行它时，三个 PickerView 就像一个.ViewController.h 文件一样工作：

       #import <UIKit/UIKit.h>

      @interface ViewController : UIViewController<UIPickerViewDataSource, UIPickerViewDelegate>
      @property (weak, nonatomic) IBOutlet UIPickerView *picker;
      @property (weak, nonatomic) IBOutlet UIPickerView *picker2;
      @property (weak, nonatomic) IBOutlet UIPickerView *picker3;
      @end

Answer 1

调用的委托和数据源方法对于所有选择器视图都是相同的。不同之处在于传递给方法的 pickerView 参数。因此，例如，而不是：

- (int)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return _pickerData.count;
}
- (int)picker2View:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return _pickerData2.count;
}
- (int)picker3View:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return _pickerData3.count;
}

你应该有：

- (int)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    if (pickerView == self.picker) {
        return _pickerData.count;
    } else if (pickerView == self.picker2) {
        return _pickerData2.count;
    } else if (pickerView == self.picker3) {
        return _pickerData3.count;
    }
}

对于所有其他委托/数据源方法，依此类推。

Answer 2

您不需要实现 3 个不同的 (int)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger) 组件。我假设您有 3 个文本字段，当用户点击 TextField 时应该显示 UIPickerView。你也不需要 3 个不同的 UIPickerViews

您将需要三个布尔值 Bool firstTextFieldActive、Bool secondTextFieldActive、Bool thirdTextFieldActive，在 viewDidLoad 中将所有这些设置为默认“NO”。

一旦用户点击特定的 TextField，将其相应的布尔值设置为“YES”

例如：假设用户点击“max”，然后编译器调用“(BOOL)textFieldShouldBeginEditing:(UITextField *)textField”，在这里您将使用以下代码检查正在编辑哪个文本字段

-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
    if([textField isEqual: max]){

        //First textfield is being edited
        firstTextFieldActive = YES;
        //Make sure the other textfield actives are set to NO
        secondTextFieldActive = NO;
        thirdTextFieldActive = NO;
        //Now reload pickerView
        [picker reloadAllComponents];
    }
}

在你的

之后

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

    if(firstTextFieldActive){
        return _pickerData.count;
    }else if(secondTextFieldActive){
        return _pickerData2.count;
    }else if(thirdTextFieldActive){
        return _pickerData3.count;
    }
}

也只实现其中之一

-(NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component                    
{
    if(firstTextFieldActive){
        self->max.text = [NSString stringWithFormat:@"%@", _pickerData[row]];

        return _pickerData[row];
    }else if(secondTextFieldActive){
        self->m2.text = [NSString stringWithFormat:@"%@", _pickerData2[row]];
        return _pickerData2[row];
    }else if(thirdTextFieldActive){
        self->m3.text = [NSString stringWithFormat:@"%@", _pickerData2[row]];
        return _pickerData3[row];
    }
}

希望对您有所帮助

Answer 3

您重复了委托方法 - 这不是委托方法的工作方式。 上述 6 种方法中唯一有效的方法将是每组中的第一种 - 这些是您的 UIPickerView 将调用的实际委托方法。其他人永远不会受到打击。这就是为什么他们的行为似乎都一样。

传递给委托方法的 pickerView 参数已经告诉您它是 3 个中的哪一个。 您需要通过将传入方法的选项与您在 viewController 的 .h 中声明的 @property 进行比较来获取 pickerView。此外，它们可能不需要在 .h 中。

 //The following is the only one of the 3 "titleForRow" methods that's working
 - (NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:           (NSInteger)component                    
   {
   //...result is that they're all set to the same array value Don't use the following line.
   //self->max.text = [NSString stringWithFormat:@"%@", _pickerData[row]];

  //use this instead to determine which UIPicker the argument `pickerView` refers to
  if (pickerView == self.picker) {
    return _pickerData[row]; //this assumes the data array has an NSString value for this row. What if it doesn't?  
   } else if ... //looks like pbasdf already mentioned this approach above... Account for the 3 options

   return nil; //after all the if/else branches, in case pickerView or row are nil, since you have to return something  
}


- (int)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
 {
     //check the "pickerView" argument against your @properties. @pbasdf beat me to it! 
    //Same if/else check as the other delegate methods
    //then return the correct _pickerData.count; //
  }