ios / xcode / objective-c：UIPickerView不顯示

Question

我有一個UIPickerView，它顯示在情節提要中，但是如果我在編譯程序時更改背景顏色，則它是不可見的，或者最好是一個彩色塊。 我是否需要用數據填充它才能顯示，即編譯后它不再顯示庫比蒂諾，山景城等嗎？

順便說一句，我試圖用數據填充選擇器視圖，但仍然不可見：

    code:
    in .h file:
@interface pickerVC : UIViewController<UIPickerViewDelegate,UIPickerViewDataSource>
    @property (weak, nonatomic) IBOutlet UIPickerView *pickerView;
    @property (strong, nonatomic) IBOutlet UILabel *color;
    @property (strong, nonatomic)          NSArray *myArray;

    in viewdidload;
       UIPickerView *pickerView;
        pickerView.delegate = self;
        _myArray  = [[NSArray alloc]         initWithObjects:@"Blue",@"Green",@"Orange",@"Purple",@"Red",@"Yellow" , nil];


    //PICKER METHODS
    // tell the picker how many rows are available for a given component
    - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
     //   NSUInteger numRows = 3;

        return _myArray.count;
    }

    // tell the picker how many components it will have
    - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
        return 1;
    }

    // tell the picker the title for a given component
    - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
        NSString *title;

        title = _myArray[row];

        return title;
    }

    // tell the picker the width of each row for a given component
    - (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component {
        int sectionWidth = 300;

        return sectionWidth;
    }
    - (void)pickerView:(UIPickerView *)pickerView didSelectRow: (NSInteger)row inComponent:(NSInteger)component{
    NSLog(@"Selected Row %d", row);
    switch(row){
        // Handle the selection
    }

Answer 1

是的，您需要實現數據源和選擇器視圖委托。

Answer 2

是的，它沒有顯示。 您必須設置picker視圖的委托和數據源，並在controller.m文件中實現委托方法。 例如

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    return 1;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return 10;
}
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    return @"ABC";
}

Answer 3

首先，在您的.h文件中添加此<UIPickerViewDelegate,UIPickerViewDataSource> ，之后再添加Delegate方法

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    return 1;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return 5;
}
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    return @"xyz";
}