了解UIPickerView的工作原理-Java 学习之路

相当新的，我需要一只手了解UIPickerViews .

我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...但我接下来添加另一个UIPickerView，如下所示：

@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，他们两个有五行 . 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？谢谢 .

1 回答

您只有两个PickerViews的委托方法;这是我不喜欢iOS的东西，但你真的没有选择 .

你必须自己离开这个 .

委托方法中的 pickerView 参数是分配了行数的选择器视图 .

请注意，这对于iOS的任何常用委托方法都有效，它是pickerview的numberOfRows，或者是tableview，或者是collectionView，或者是参数中包含视图的任何委托方法 .

容易理解的方法是将您的pickerview作为您的类（或属性）的字段，并简单地将参数与它进行比较 .

@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;
}

回复于 2024-04-26T16:48:36+08:00

了解UIPickerView的工作原理

1 回答

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