通过脚本或 Storyboard 动态关闭 UIPickerView

Question

我在 iOS 上实现 UIPickerView 时遇到很多问题。 我想显示一个选择器来填充某个字段，但仅当选择该字段时才显示，并在其他情况下关闭（或隐藏）选择器。可能有动画。

• 故事板：

我能够通过插座引用它，填充并在我的 ViewController 上显示它。但我无法使用 Storyboard 动态关闭（或隐藏） UIPickerView。 我尝试过：

pickerView.hidden = YES;

但没有成功。有什么想法吗？

---

• 编码

我尝试以编程方式实现我的选取器：

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
//if click on fieldWithPicker, dismiss the keyaboard and load the picker
if (textField == fieldWithPicker)
{        
    //dismiss the keyboard of fieldWithoutPicker
    [fieldWithoutPicker resignFirstResponder];
    // Check if the picker is already on screen. If so, skip creating picker view and go to handling choice
    if (myPickerView.superview == nil)
    {           
        //Make picker
        myPickerView = [[UIPickerView alloc] initWithFrame:CGRectZero];
        CGSize pickerSize = [myPickerView sizeThatFits:CGSizeZero];
        myPickerView.frame = [self pickerFrameWithSize:pickerSize];
        myPickerView.autoresizingMask = UIViewAutoresizingFlexibleWidth;
        myPickerView.showsSelectionIndicator = YES;
        // this view controller is the data source and delegate
        myPickerView.delegate = self;
        myPickerView.dataSource = self;

        // Add the picker
        [self.view.window addSubview: myPickerView];

        // size up the picker view to our screen and compute the start/end frame origin for our slide up animation
        // compute the start frame
        CGRect screenRect = [[UIScreen mainScreen] applicationFrame];
        CGRect startRect = CGRectMake(0.0, screenRect.origin.y + screenRect.size.height, pickerSize.width, pickerSize.height);
        mypickerView.frame = startRect;
        // compute the end frame
        CGRect pickerRect = CGRectMake(0.0, screenRect.origin.y + screenRect.size.height - pickerSize.height-100, pickerSize.width, pickerSize.height);

        // start the slide up animation
        [UIView beginAnimations:nil context:NULL];
        [UIView setAnimationDuration:PICKER_ANIMATION_DURATION];
        // Give time for the table to scroll before animating the picker's appearance
        [UIView setAnimationDelay:PICKER_ANIMATION_DELAY];

        // we need to perform some post operations after the animation is complete
        [UIView setAnimationDelegate:self];
        myPickerView = pickerRect;
        [UIView commitAnimations];
    }
    //we don't want keyboard, since we have a picker
    return NO;
}

//if click on fieldWithoutPicker, dismiss the picker and load the keyboard
if (textField == fieldWithoutPicker)
{
    [self hidePickerContinenteView];
}
return YES;
}

然后我实现了我的hidePickerContinenteView函数以移出选取器：

- (void) hidePickerContinenteView
{
CGRect screenRect = [[UIScreen mainScreen] applicationFrame];
CGRect endFrame = self.view.frame;
endFrame.origin.y = screenRect.origin.y + screenRect.size.height;

// start the slide down animation
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:PICKER_ANIMATION_DURATION];

// we need to perform some post operations after the animation is complete
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(slideDownDidStop)];

pickerContinenteView.frame = endFrame;
[UIView commitAnimations];
}

此时我有两个主要问题：

• 在 textFieldShouldBeginEditing 方法中，我检查 PickerView 是否已存在，以防万一什么也不做。在 hidePickerContinenteView 方法中，我隐藏了 Picker，但 PickerView 仍然存在：这意味着下次我单击 fieldWithPicker 时，不会显示 Picker。 我尝试在 hidePickerContinenteView 方法中使用以下内容： [pickerContinenteView removeFromSuperview]; 但这会立即关闭 PickerView 并且根据此，不会显示任何动画。 有什么想法吗？

• 如果显示选取器并且用户更改视图，例如单击另一个选项卡或后退按钮，则不会关闭选取器。对此还有什么想法吗？

先感谢您， 亚萨

Answer 1

我将通过创建选择器并将其放置在故事板中您希望它可见和使用时所在的位置来解决此问题。选中属性检查器中的隐藏框，以便在加载视图时它将隐藏。确保它位于故事板中任何其他视图的顶部。然后对视图控制器进行编码以使用隐藏属性来显示它并再次隐藏。您仍然可以使用动画来更改隐藏属性。

要隐藏选择器，请使用：

[templatePicker setHidden:YES];

并显示选择器，请使用：

[templatePicker setHidden:NO];