复选框值/无MVVM Xamarin
我有一组复选框，需要它们来更改值。。如果一个被选中，另一个应该被取消选中。不想实现MVVM的原因是，这只是现有应用程序的新前端，我只需要在合并项目之前让它们工作。这就是我拥有的，但它不起作用，我得到null reference/System.NullReferenceException:“对象引用未设置为对象的实例。” 我的密码里有这个复选框值/无MVVM Xamarin,xamarin,xamarin.forms,Xamarin,Xamarin.forms,我有一组复选框，需要它们来更改值。。如果一个被选中，另一个应该被取消选中。不想实现MVVM的原因是，这只是现有应用程序的新前端，我只需要在合并项目之前让它们工作。这就是我拥有的，但它不起作用，我得到null reference/System.NullReferenceException:“对象引用未设置为对象的实例。” 我的密码里有这个 private void AdvancedCheckBox_IsCheckedChanged(object sender, IsCheckedChangedEv
private void AdvancedCheckBox_IsCheckedChanged(object sender, IsCheckedChangedEventArgs e)
{
if (AdvancedCheckBox.IsChecked == true) //System.NullReferenceException: 'Object reference not set to an instance of an object.'
{
AllCheckBox.IsChecked = false;
UpperIntermediateCheckBox.IsChecked = false;
AdvancedCheckBox.IsChecked = false;
}
else
AdvancedCheckBox.IsChecked = true;
}
private void UpperIntermediateCheckBox_IsCheckedChanged(object sender, IsCheckedChangedEventArgs e)
{
if (UpperIntermediateCheckBox.IsChecked == true)
{
AllCheckBox.IsChecked = false;
UpperIntermediateCheckBox.IsChecked = false;
AdvancedCheckBox.IsChecked = false;
}
else
UpperIntermediateCheckBox.IsChecked = true;
}
private void IntermediateCheckBox_IsCheckedChanged(object sender, IsCheckedChangedEventArgs e)
{
CheckBox IntermediateCheckBox = sender as CheckBox;
if (IntermediateCheckBox.IsChecked == false)
{
AllCheckBox.IsChecked = false;
UpperIntermediateCheckBox.IsChecked = false;
AdvancedCheckBox.IsChecked = false ;
}
else
IntermediateCheckBox.IsChecked = true ;
}
private void AllCheckBox_IsCheckedChanged(object sender, IsCheckedChangedEventArgs e)
{
CheckBox AllCheckBox = sender as CheckBox;
if (AllCheckBox.IsChecked == true) System.NullReferenceException: 'Object reference not set to an instance of an object.'
{
UpperIntermediateCheckBox.IsChecked = false;
AdvancedCheckBox.IsChecked = false;
IntermediateCheckBox.IsChecked = false;
}
else
AllCheckBox.IsChecked = true;
}
<StackLayout Grid.Row="0"
Orientation="Horizontal"
Spacing="10"
HorizontalOptions="Start">
<grial:Checkbox x:Name="AllCheckBox"
IsCheckedChanged ="AllCheckBox_IsCheckedChanged"
HorizontalOptions="Start">
<Label
Margin="10,0"
FontSize="19"
Text="{ grial:Translate A_LabelAllArticles}"
VerticalOptions="Center"
TextColor="{ DynamicResource AccentColor }" />
</grial:Checkbox>
</StackLayout>
<StackLayout Grid.Row="1"
Orientation="Horizontal"
Spacing="10"
HorizontalOptions="Start">
<grial:Checkbox x:Name="BeginnerCheckBox"
IsChecked="false"
HorizontalOptions="Start">
<Label
FontSize="19"
Margin="10,0"
Text="{ grial:Translate A_LabelBeginnerArticles}"
VerticalOptions="Center"
TextColor="{ DynamicResource AccentColor }" />
</grial:Checkbox>
</StackLayout>
<StackLayout Grid.Row="2"
Orientation="Horizontal"
Spacing="10"
HorizontalOptions="Start">
<grial:Checkbox x:Name="IntermediateCheckBox"
IsCheckedChanged="IntermediateCheckBox_IsCheckedChanged"
HorizontalOptions="Start">
<Label
FontSize="19"
Margin="10,0"
Text="{ grial:Translate A_LabelIntermediateArticles}"
VerticalOptions="Center"
TextColor="{ DynamicResource AccentColor }" />
</grial:Checkbox>
</StackLayout>
<StackLayout Grid.Row="3"
Orientation="Horizontal"
Spacing="10"
HorizontalOptions="Start">
<grial:Checkbox x:Name="UpperIntermediateCheckBox"
IsCheckedChanged="UpperIntermediateCheckBox_IsCheckedChanged"
HorizontalOptions="Start">
<Label
FontSize="19"
Margin="10,0"
Text="{ grial:Translate A_LabelUpperIntermediateArticles}"
VerticalOptions="Center"
TextColor="{ DynamicResource AccentColor }" />
</grial:Checkbox>
</StackLayout>
<StackLayout Grid.Row="4"
Orientation="Horizontal"
Spacing="10"
HorizontalOptions="Start">
<grial:Checkbox x:Name="AdvancedCheckBox"
IsCheckedChanged="AdvancedCheckBox_IsCheckedChanged"
HorizontalOptions="Start">
<Label
FontSize="19"
Margin="10,0"
Text="{ grial:Translate A_LabelAdvancedArticles}"
VerticalOptions="Center"
TextColor="{ DynamicResource AccentColor }" />
</grial:Checkbox>
您使用的是Grial UIKit中的复选框，但将发送者定义为本机Xamarin。如果是Forms复选框，请使用Grial复选框作为发送者的强制类型
//This will make every checkbox to checked or unchecked depending of the state of the clicked one
private void AllCheckBox_IsCheckedChanged(object sender, IsCheckedChangedEventArgs e)
{
CheckBox ClickedCheckbox = sender as UXDivers.Grial.Checkbox;
ChangeAllCheckboxesTo(ClickedCheckbox.IsChecked != null ? ClickedCheckbox.IsChecked : false);
}
//This will make every checkbox to false if you select one
private void AnyCheckBox_IsCheckedChanged(object sender, IsCheckedChangedEventArgs e)
{
CheckBox ClickedCheckbox = sender as UXDivers.Grial.Checkbox;
bool WasSelected = ClickedCheckbox.IsChecked != null ? ClickedCheckbox.IsChecked != null : false;
ChangeAllCheckboxesTo(false);
if(!WasSelected)
ClickedCheckbox.IsChecked = true;
}
public void ChangeAllCheckboxesTo(bool value)
{
try
{
UpperIntermediateCheckBox.IsChecked = value;
AdvancedCheckBox.IsChecked = value;
IntermediateCheckBox.IsChecked = value;
}
catch(Exception ex)
{
}
}
您的前三个方法在IF中有相同的语句-这似乎不正确是的，我尝试了不同的方法我添加了一个anwser，但我没有太多的上下文说明是什么导致了nullexception，您能将该信息添加到问题中吗？如果需要，我很乐意更新我的anwserto@Ricardo迪亚斯·莫瑞斯你好，这看起来很棒。但我也有同样的例外。我想我遗漏了什么。这是下划线和（ClickedCheckbox.IsChecked！=null？这是输出结果，结果始终为null，因为它从不等于类型的nullbool@RicardoDias Morais bool wassected=ClickedCheckbox.IsChecked！=null？ClickedCheckbox.IsChecked！=null:false；System.NullReferenceException:“对象引用未设置为对象的实例。”