Question

我的comboBox上有一个简单的Winform控件。我想设置一个comboBox项，作为将在表单加载时显示的默认项：

duration_ComboBox.SelectedItem = duration_ComboBox.Items.IndexOf("0 minutes");
        duration_ComboBox.Text = duration_ComboBox.SelectedText;

我在comboBox中有 0分钟项，但在加载时，该字段仍为空。
有什么想法吗？

Answer 1

main.cpp: In function 'int main()':
main.cpp:6:46: error: call to non-constexpr function 'constexpr std::array<_Tp, _Nm>::size_type std::array<_Tp, _Nm>::size() const [with _Tp = std::vector<int>; long unsigned int _Nm = 4ul; std::array<_Tp, _Nm>::size_type = long unsigned int]'
     std::array<std::vector<double>, arr1.size()> arr2;
                                              ^
In file included from main.cpp:1:0:
/usr/local/include/c++/5.3.0/array:170:7: note: 'constexpr std::array<_Tp, _Nm>::size_type std::array<_Tp, _Nm>::size() const [with _Tp = std::vector<int>; long unsigned int _Nm = 4ul; std::array<_Tp, _Nm>::size_type = long unsigned int]' is not usable as a constexpr function because:
       size() const noexcept { return _Nm; }
       ^
/usr/local/include/c++/5.3.0/array:170:7: error: enclosing class of constexpr non-static member function 'constexpr std::array<_Tp, _Nm>::size_type std::array<_Tp, _Nm>::size() const [with _Tp = std::vector<int>; long unsigned int _Nm = 4ul; std::array<_Tp, _Nm>::size_type = long unsigned int]' is not a literal type
/usr/local/include/c++/5.3.0/array:89:12: note: 'std::array<std::vector<int>, 4ul>' is not literal because:
     struct array
            ^
/usr/local/include/c++/5.3.0/array:89:12: note:   'std::array<std::vector<int>, 4ul>' has a non-trivial destructor
main.cpp:6:46: error: call to non-constexpr function 'constexpr std::array<_Tp, _Nm>::size_type std::array<_Tp, _Nm>::size() const [with _Tp = std::vector<int>; long unsigned int _Nm = 4ul; std::array<_Tp, _Nm>::size_type = long unsigned int]'
     std::array<std::vector<double>, arr1.size()> arr2;
                                              ^
main.cpp:6:48: note: in template argument for type 'long unsigned int' 
     std::array<std::vector<double>, arr1.size()> arr2;
                                                ^

Answer 2

设置Combo.SelectedItem。

，而不是设置Combo.SelectedIndex

duration_ComboBox.SelectedIndex = duration_ComboBox.Items.IndexOf（＆＃34; 0分钟＆＃34;）;

希望这有帮助。

Winform ComboBox-无法设置默认值

2 个答案: