我有3个Comboboxes。一个用于COM端口，一个用于波特率，一个用于延迟。有一次，他们都工作了，但由于一些奇怪的原因，它不再有效。在我加载表单之前没有例外，然后我得到一个NullPointerException。之所以会发生这种情况，是因为我的Load事件没有被触发，而且有些人搜索某人建议他们的DataSource应该受到指责。果然我注释掉了我的DataSource，我不再有空指针异常。
但令我困惑的是为什么。
this.comportCombo.DataSource = System.IO.Ports.SerialPort.GetPortNames();
this.comportCombo.Dock = DockStyle.Fill;
this.comportCombo.SelectedValueChanged += comportCombo_SelectedValueChanged;
this.baudRatCombo.DataSource = new int[] { 4800, 9600, 19200, 115200 };
this.baudRatCombo.Dock = DockStyle.Fill;
this.baudRatCombo.SelectedValueChanged += baudRatCombo_SelectedValueChanged;
this.delayCombo.DataSource = new int[] { 50, 100, 200, 300, 400, 500 }; //Code I comment out to stop the NPE.
this.delayCombo.Dock = DockStyle.Fill;
this.delayCombo.SelectedValueChanged += delayCombo_SelectedValueChanged;
BaudRatCombo工作正常。所以我尝试了一个愚蠢的解决方案，只放4个数字，但仍然没有。我对此完全感到困惑。我的调试器对此也没有太多帮助。有什么建议？我已经尝试评论dalyCombo.DataSource（摆脱我的NPE）我已经尝试评论出其他2个组合框。我不知所措。请帮忙。
更新
public class IInputDialog : Form
{
public IInputDialog()
{
InitializeComponent();
this.Load += SerialPortDialog_Load;
}
public IInputDialog(IInput iinput)
: this()
{
this._iinput = iinput;
}
void SerialPortDialog_Load(object sender, EventArgs e)
{
//Doesn't Fire with DelayCombo.DataSource
if (this._iinput != null)
{
serialPortTablePanel.IInput = this._iinput;
}
}
public static IInput GetIInputDialog(IInput iinput)
{
IInput temp = iinput;
using (IInputDialog icb = new IInputDialog(iinput))
{
if (icb.ShowDialog() == DialogResult.OK)
temp = icb.serialPortTablePanel.IInput;
}
return temp;
}
private void InitializeComponent()
{
this.SuspendLayout();
this.serialPortTablePanel = new IInputTablePanel();
this.serialPortTablePanel.Dock = DockStyle.Fill;
this.Controls.Add(serialPortTablePanel);
this.MinimumSize = new System.Drawing.Size(501, 562);
this.ResumeLayout(false);
}
private IInputTablePanel serialPortTablePanel;
private IInput _iinput;
}
SerialPortWedgeTablePanel（部分）
internal class IInputTablePanel : Control
{
internal IInputTablePanel()
{
InitializeComponent();
}
private void InitializeComponent()
{
SetupTestGroupBox(ref gb1, ref split1);
tbl.Controls.Add(gb1, 0, 2);
}
private void SetupTestGroupBox(ref GroupBox gb1, ref SplitContainer split1)
{
this.comportCombo.DataSource = System.IO.Ports.SerialPort.GetPortNames();
this.comportCombo.Dock = DockStyle.Top;
this.comportCombo.SelectedValueChanged += comportCombo_SelectedValueChanged;
this.baudRatCombo.DataSource = new int[] { 4800, 9600, 19200, 115200 };
this.baudRatCombo.Dock = DockStyle.Top;
this.baudRatCombo.SelectedValueChanged += baudRatCombo_SelectedValueChanged;
this.delayCombo.DataSource = new int[] { 50, 100, 200, 300, 400, 500 };
this.delayCombo.Dock = DockStyle.Top;
this.delayCombo.SelectedValueChanged += delayCombo_SelectedValueChanged;
gb1.Controls.Add(split1);
gb1.Controls.Add(delayCombo);
gb1.Controls.Add(baudRatCombo);
gb1.Controls.Add(comportCombo);
//gb1.Controls.Add(GetDefaultGroupBox("Input Delay", delayCombo));
//gb1.Controls.Add(GetDefaultGroupBox("Baud Rate", baudRatCombo));
//gb1.Controls.Add(GetDefaultGroupBox("Port Name", comportCombo));
gb1.Dock = DockStyle.Fill;
gb1.Enabled = false;
gb1.Font = new Font("Arial", 10F, FontStyle.Regular, GraphicsUnit.Point, 0x00);
gb1.Margin = new Padding(0);
gb1.Padding = new Padding(10, 3, 10, 10);
gb1.Text = "Serial Port Options";
}
void delayCombo_SelectedValueChanged(object sender, EventArgs e)
{
_iinput.Delay = (int)this.delayCombo.SelectedItem;
}
void baudRatCombo_SelectedValueChanged(object sender, EventArgs e)
{
_serialPort.BaudRate = (int)baudRatCombo.SelectedItem;
}
void comportCombo_SelectedValueChanged(object sender, EventArgs e)
{
_serialPort.PortName = comportCombo.SelectedItem.ToString();
}
internal IInput IInput
{
get {return _iinput;}
set
{
this._iinput = value;
this.delayCombo.SelectedItem = value.Delay;
if (value is ComPortInput)
{
this.comportCombo.SelectedItem = (value as ComPortInput).serialPort.PortName; //string[]
this.baudRatCombo.SelectedItem = (value as ComPortInput).serialPort.BaudRate; //object[]
_serialPort = (value as ComPortInput).serialPort;
}
}
}
private void SuspendLayouts(params Control[] args)
{
this.SuspendLayout();
foreach(Control c in args)
c.SuspendLayout();
}
private void ResumeLayouts(bool resume, params Control[] args)
{
foreach (Control c in args)
c.ResumeLayout(resume);
this.ResumeLayout(resume);
}
private Button testButt;
private ClickComboBox comportCombo = new ClickComboBox();
private ClickComboBox baudRatCombo = new ClickComboBox();
private ClickComboBox delayCombo = new ClickComboBox();
private System.IO.Ports.SerialPort _serialPort = new System.IO.Ports.SerialPort();
private IInput _iinput;
}
internal class ClickComboBox : System.Windows.Forms.ComboBox
{
internal ClickComboBox()
{
this.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;
this.Font = new System.Drawing.Font("Microsoft Sans Serif", 24F);
this.FormattingEnabled = true;
this.ItemHeight = 37;
this.Click += ClickComboBox_Click;
}
void ClickComboBox_Click(object sender, System.EventArgs e)
{
this.BeginInvoke(new System.Action(() => this.DroppedDown = true));
}
}
UPDATE2
我刚试过这个，它按预期工作......
this.delayCombo.Items.AddRange(new object[] { 50, 100, 200, 300, 400, 500 });
this.delayCombo.Dock = DockStyle.Top;
this.delayCombo.SelectedValueChanged += delayCombo_SelectedValueChanged;