Question

我有这个非常简单的代码，或者至少我认为这很简单。

// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {  
CGRect rect = CGRectMake(0.0f, 20.0f, 320.0f, 216.0f); 

UIPickerView *myPickerView = [[UIPickerView alloc] initWithFrame:rect]; 

self.view = myPickerView;
[myPickerView release];
}

我正在使用XCode运行一般的基于视图的模板。我可以看到loadView被调用，但我得到一个黑框而不是UIPickerView。

我做错了什么？

/ donnib

Answer 1

您是否实施了选择器的数据源方法？你需要它，否则它不会显示。

此处链接到Apple文档：http://developer.apple.com/library/ios/#DOCUMENTATION/iPhone/Reference/UIPickerViewDataSource_Protocol/Reference/Reference.html#//apple_ref/occ/intf/UIPickerViewDataSource

Answer 2

您忘记将UIPickerView的委托设置为当前视图。添加：

myPickerView.delegate = self;

...在初始化之后和您的观点之前。当然，请确保将头文件设置为UIPickerView委托并实现dataSource方法。

Answer 3

试试这个：

UIView *contentView = [[UIView alloc] initWithFrame: [[UIScreen mainscreen] bounds]];
UIPickerView *pickerView = [[UIPickerView alloc] initWithFrame: CGRectZero];
CGSize pickerSize = [pickerView sizeThatFits: CGSizeZero];
pickerView.frame = [self pickerFrameWithSize: pickerSize];
[pickerView setShowsSelectionIndicator: YES];
[contentView addSubview: pickerView];
[pickerView release];
[self setView: contentView];
[contentView release];

Answer 4

您应该覆盖-loadView，而不是覆盖-viewDidLoad。加载视图后，您将创建选择器并将其添加为视图控制器拥有的视图的子视图。

- (void)viewDidLoad
{
    [super viewDidLoad];

    CGRect rect = CGRectMake(0.0f, 20.0f, 320.0f, 216.0f); 
    UIPickerView *myPickerView = [[UIPickerView alloc] initWithFrame:rect];
    [self.view addSubview:myPickerView];
    [myPickerView release];
}

为什么我得到一个黑框而不是选择器？

4 个答案: