GridViewCheckBoxColumn以CheckBox的形式显示、编辑bool值,实现行选中效果。
如果需要在表头添加全选框,可以将EnableHeaderCheckBox设置为true:
private void AddCheckColumn()
{
checkColumn = new GridViewCheckBoxColumn();
checkColumn.Name = "Select";
checkColumn.HeaderText = "All";
checkColumn.EnableHeaderCheckBox = true;
this.radGridView1.Columns.Insert(0, checkColumn);
this.radGridView1.HeaderCellToggleStateChanged += RadGridView1_HeaderCellToggleStateChanged;
}
private void RadGridView1_HeaderCellToggleStateChanged(object sender, GridViewHeaderCellEventArgs e)
{
MessageBox.Show($"状态:{e.State}");
}
通过监听RadGridView的HeaderCellToggleStateChanged事件监听表头的全选框状态。除了切换表头的全选框状态时会触发该事件,切换列的CheckBox时如果同时切换了表头的全选框状态,也会触发该事件。
问题:
使用过程中,发现GridView隐藏再显示会报空指针异常。
分析
报错发生在GridView设置只读属性的位置,异常调用堆栈如下:
at Telerik.WinControls.UI.GridCheckBoxHeaderCellElement.UpdateCheckboxReadOnly()
at Telerik.WinControls.UI.GridCheckBoxHeaderCellElement.MasterTemplate_PropertyChanged(Object sender, PropertyChangedEventArgs e)
at System.ComponentModel.PropertyChangedEventHandler.Invoke(Object sender, PropertyChangedEventArgs e)
at Telerik.WinControls.UI.GridViewTemplate.OnNotifyPropertyChanged(PropertyChangedEventArgs e)
at Telerik.WinControls.UI.MasterGridViewTemplate.OnNotifyPropertyChanged(PropertyChangedEventArgs e)
at Telerik.WinControls.UI.GridViewTemplate.SetProperty[T](String propertyName, T& propertyField, T value)
at Telerik.WinControls.UI.MasterGridViewTemplate.set_GridReadOnly(Boolean value)
at Telerik.WinControls.UI.RadGridView.set_ReadOnly(Boolean value)
at CheckBoxInHeader_csharp.RadForm1.<AddButton>b__8_2(Object o, EventArgs e) in \CheckBoxInHeader_csharp\RadForm1.cs:line 82
根据异常调用堆栈,发现是在Telerik内部报错,直接反编译调试下,在GridCheckBoxHeaderCellElement.UpdateCheckboxReadOnly()处设置断点,看看为什么导致空指针。查看this无法计算表达式,可以编辑下方法,加几个判断:
可以看到,this.ColumnInfo为空。继续调试,发现EnableHeaderCheckBox设置为true的列如果被隐藏,当设置GridView的Readonly属性的时候就会触发该异常,这是UI框架的BUG。
解决
可以自己实现GridCheckBoxHeaderCellElement,不用官方的,参考文档,这比较麻烦。简单处理,加个try-catch捕获下吧。以下是测试代码,先点击测试1,再点击测试2就会触发该异常。
public partial class RadForm1 : RadForm
{
private bool flag1 = false;
private bool flag2 = false;
private GridViewCheckBoxColumn checkColumn;
public RadForm1()
{
InitializeComponent();
AddCheckColumn();
AddButton();
this.radGridView1.RowCount = 10;
this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
this.radGridView1.MasterTemplate.AllowAddNewRow = false;
}
private void AddCheckColumn()
{
checkColumn = new GridViewCheckBoxColumn();
checkColumn.Name = "Select";
checkColumn.HeaderText = "All";
checkColumn.EnableHeaderCheckBox = true;
this.radGridView1.Columns.Insert(0, checkColumn);
this.radGridView1.HeaderCellToggleStateChanged += RadGridView1_HeaderCellToggleStateChanged;
this.radGridView1.Columns.Add(new GridViewTextBoxColumn("A"));
this.radGridView1.Columns.Add(new GridViewTextBoxColumn("B"));
}
private void RadGridView1_HeaderCellToggleStateChanged(object sender, GridViewHeaderCellEventArgs e)
{
MessageBox.Show($"状态:{e.State}");
}
private void AddButton()
{
Button btn1 = new Button();
btn1.Text = "测试1";
btn1.Click += (o, e) =>
{
checkColumn.IsVisible = flag1;
flag1 = !flag1;
};
btn1.Location = new Point(5, 5);
this.Controls.Add(btn1);
Button btn2 = new Button();
btn2.Text = "测试2";
btn2.Click += (o, e) =>
{
if (flag2)
radGridView1.Hide();
else
{
radGridView1.Show();
try
{
radGridView1.ReadOnly = flag2;
}
catch { }
}
flag2 = !flag2;
};
btn2.Location = new Point(120, 5);
this.Controls.Add(btn2);
}
}
标签:Telerik,导致,EnableHeaderCheckBox,checkColumn,private,radGridView1,UI,new,指针
From: https://www.cnblogs.com/louzixl/p/17585628.html