Question

相当新，我需要了解UIPickerViews。

我已经以编程方式为我的项目创建了一个UIPickerView：

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    UIPickerView *myPickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 200, 375, 200)];
    myPickerView.delegate = self;
    myPickerView.showsSelectionIndicator = YES;
    [self.view addSubview:myPickerView];   
}

然后为行数添加了一个方法：

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    NSUInteger numRows = 5;

    return numRows;
}

返回预期的五个问号。然后我可以继续创建一个数组来填充这些行等......但是我接下来会添加另一个UIPickerView：

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    UIPickerView *myPickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 200, 375, 200)];
    myPickerView.delegate = self;
    myPickerView.showsSelectionIndicator = YES;
    [self.view addSubview:myPickerView];

    UIPickerView *my2PickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 400, 375, 200)];
    my2PickerView.delegate = self;
    my2PickerView.showsSelectionIndicator = YES;
    [self.view addSubview:my2PickerView];
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    NSUInteger numRows = 5;

    return numRows;
}

现在我有两个pickerview控制器，它们共有五行。我的问题是如何选择该方法适用的哪个pickerview，也可以解释为什么该方法适用于项目中的所有pickerview？感谢。

Answer 1

两个PickerView只有一个委托方法;这是我不喜欢iOS的东西，但你真的没有选择。

你必须自己if-statement。

委托方法中的pickerView参数是分配了行数的选择器视图。

请注意，这适用于iOS的任何常用委托方法，无论是pickerview的numberOfRows，还是tableview，collectionView，还是参数中包含视图的任何委托方法。 / p>

易于理解的方法是将您的选择器视图作为您的类（或属性）的字段，并简单地将参数与其进行比较。

@interface ViewController ()
@property (weak, nonatomic) UIPickerView *_mySexyPickerView;
@property (weak, nonatomic) UIPickerView *_myOtherPickerView;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    _mySexyPickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 200, 375, 200)];
    _mySexyPickerView.delegate = self;
    _mySexyPickerView.showsSelectionIndicator = YES;
    [self.view addSubview:_mySexyPickerView];

    _myOtherPickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 400, 375, 200)];
    _myOtherPickerView.delegate = self;
    _myOtherPickerView.showsSelectionIndicator = YES;
    [self.view addSubview:_myOtherPickerView];
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    if (pickerView == _mySexyPickerView){
         return 2;
    }

    if (pickerView == _myOtherPickerView){
         return 19;
    }
    return 0;
}

了解UIPickerView的工作原理

1 个答案: