应用程序在UIAlertController中UIDatePicker for UITextField的ValueCha
本文关键字:UITextField ValueCha for UIDatePicker UIAlertController 应用程序 | 更新日期: 2023-09-27 18:35:07
我实例化一个UIAlertController,并将UIDatePicker分配给它的UITextField之一作为输入视图。我还为选取器分配了一个 ValueChanged 事件处理程序。UIDatePicker 正确显示上述 UITextField 何时获得焦点,但当我更改应用程序崩溃日期的值时。
请考虑下面的代码。
var d = UIAlertController.Create( "Confirm", "Fill below with the required info.", UIAlertControllerStyle.Alert);
d.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, ((UIAlertAction obj) => SubmitAction(obj, d))));
d.AddAction(UIAlertAction.Create("Cancel", UIAlertActionStyle.Cancel, null));
d.AddTextField((delegate(UITextField obj) {
UIDatePicker picker = new UIDatePicker ();
picker.ValueChanged += (object sender, EventArgs e) => { obj.Text = picker.Date.Description; };
obj.InputView = picker;
}));
PresentViewController(d, true, null);
同样,机械臂显示正常。应用在 ValueChanged 事件上崩溃,即使使用空处理程序picker.ValueChanged += (object sender, EventArgs e) => {};
。
不添加事件处理程序不会崩溃!
此代码位于按钮 TouchUpInside 事件处理程序中。
我哪里做错了?
我认为您在代码示例中混淆了事件方法。 TouchUpInside
不会为选取器触发。如果要在选择新的日期值时更新文本视图的内容,则需要使用:
picker.ValueChanged += (pickerSender, pickerArgs) =>
{
obj.Text = picker.Date.Description;
};
为了防止这种情况崩溃,您需要保留对 UIDatePicker 实例的引用,否则收集起来会太早。最简单的方法是将日期选取器移动到类范围:
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
// Perform any additional setup after loading the view, typically from a nib.
this.btnTest.TouchUpInside += HandleTouchUpInside;
}
UIDatePicker picker;
void HandleTouchUpInside (object sender, EventArgs e)
{
var d = UIAlertController.Create( "Confirm", "Fill below with the required info.", UIAlertControllerStyle.Alert);
d.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, ((UIAlertAction obj) => {})));
d.AddAction(UIAlertAction.Create("Cancel", UIAlertActionStyle.Cancel, null));
d.AddTextField((delegate(UITextField obj) {
picker = new UIDatePicker ();
picker.ValueChanged += (pickerSender, pickerArgs) =>
{
obj.Text = picker.Date.Description;
};
obj.InputView = picker;
}));
PresentViewController(d, true, null);
}