Question

iOS很遗憾没有像标签那样的html下拉选择器。我决定我终于要为我的应用创建一个，它看起来很棒。我的下拉对象是UITextField的子类。但是，我改变了一些东西，现在它只在某些时候起作用。

已启用用户互动，但我不希望文本字段可编辑。我的dropdown子类所在的类是UITextField委托，应该接收UITextField的委托方法。

我有- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField{我检查有问题的文本字段是否是下拉菜单，如果是，我调用一个方法来实例化一个弹出窗口并禁用编辑，但下拉列表只显示在其他所有轻按。

例如，我将点击“textfield”并显示我的popover。我点击，弹出消失，然后点击“文本字段”，没有任何反应。我再次点击文本字段，然后出现弹出窗口。不知道为什么会这样，这就是我正在做的事情：

·H

subclass : UIViewController<UITextFieldDelegate>

的.m

dropdownTextField.delegate = self;
...
- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField{
    if(textField == self.measurementSelect){
        NSLog(@"IM CALLED");
        [self showPopover:textField];
        return NO;
    }
    return YES;
}

-(void)showPopover:(id)sender{
    if (_measurementPicker == nil) {
        _measurementPicker = [[iPadMeasurementSelect alloc] initWithStyle:UITableViewStylePlain];
        _measurementPicker.delegate = self;
    }

    if (_measurementPopover == nil) {
        _measurementPopover = [[UIPopoverController alloc] initWithContentViewController:_measurementPicker];
        [_measurementPopover presentPopoverFromRect:self.measurementSelect.frame inView:self.conversionView permittedArrowDirections:UIPopoverArrowDirectionLeft animated:YES];

    }
    else {
        [_measurementPopover dismissPopoverAnimated:YES];
        _measurementPopover = nil;
    }
}

每次点击都会被记录，所以我认为我的popover方法是这个问题的罪魁祸首。有什么想法吗？

Answer 1

让我们通过戏弄UI元素的存在和popover的可见状态来重写：

// canonical lazy getters for UI elements

- (iPadMeasurementSelect *)measurementPicker {
    if (!_measurementPicker) {
        _measurementPicker = [[iPadMeasurementSelect alloc] initWithStyle:UITableViewStylePlain];
        _measurementPicker.delegate = self;
    }
    return _measurementPicker;
}

- (UIPopoverController *)measurementPopover {
    if (!_measurementPopover) {
        _measurementPopover = [[UIPopoverController alloc] initWithContentViewController:self.measurementPicker];
    }
    return _measurementPopover;
}

// now the show/hide method makes sense.  it can take a bool about whether to show or hide
-(void)showPopover:(BOOL)show {

    if (show) {
        [self.measurementPopover presentPopoverFromRect:self.measurementSelect.frame inView:self.conversionView permittedArrowDirections:UIPopoverArrowDirectionLeft animated:YES];
    } else {
        [self.measurementPopover dismissPopoverAnimated:NO];
        // if you want/need to create a new one each time it is shown, nil the popover here, like this:
        // self.measurementPopover = nil;
    }
}

当textField开始编辑时，显示如下的弹出窗口：

[self showPopover:YES];

当委托获得didEndEditing消息时：

[self showPopover:NO];

每隔一次调用UITextField shouldBeginEditing？

1 个答案: